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1

Characterization of poly(vinyl acetate) based floating matrix tablets.  

PubMed

Floating Kollidon SR matrix tablets containing Propranolol HCl were developed and characterized with respect to drug release characteristics and floating strength. Kollidon SR was able to delay Propranolol HCl release efficiently. Drug release kinetics was evaluated using the Korsmeyer-Peppas model and found to be governed by Fickian diffusion. Tablet floating started immediately and continued for 24 h. It was possible to monitor the floating strength of the matrix devices using a simple experimental setup. Floating strength was related to Kollidon SR level with improved floating characteristics for samples with a high polymer/drug ratio. Swelling characteristics of the tablets were analyzed by applying the equation according to Therien-Aubin et al. The influence of the polymer content on swelling characteristics was found to be only marginal. Furthermore, the new method of benchtop MRI was introduced to study the water diffusion and swelling behaviour non-invasively and continuously. PMID:18180069

Strübing, Sandra; Metz, Hendrik; Mäder, Karsten

2008-03-01

2

Sustained delivery of captopril from floating matrix tablets.  

PubMed

The development of a controlled release formulation of captopril has been a challenge for some time. In this work, the in vitro sustained release of captopril from Metolose SH 4000 SR/sodium bicarbonate floating tablets has been studied, varying the proportions of Metolose and bicarbonate. This was studied at two different compaction pressures. Other studied variables include the kinetics of the hydration volume, the matrices floating time and the matrix density. The results show that matrices compacted at 55 MPa float in the dissolution medium for more than 8h while those compacted at 165 MPa float only when sodium bicarbonate is included in the formulation. The increase of the matrix polymer proportion increases the maximal hydration volume as well as the time to attain this maximum. The matrices hydration volume increases with the inclusion of sodium bicarbonate in the formulation. The matrix density is lower when compacted at 55 MPa. The drug release constant (k) decreases and the exponent indicative of the release mechanism (n) increases with increasing polymer contents. The drug released with time is lesser when sodium bicarbonate is included in the formulation. Carbon dioxide bubbles obstruct the diffusion path and decrease the matrix coherence. The effect of compaction pressure to reduce the drug release rate has to be made clear in further studies. PMID:18588962

Jiménez-Martínez, Inéz; Quirino-Barreda, Tomás; Villafuerte-Robles, Leopoldo

2008-10-01

3

Studies on formulation and in vitro evaluation of floating matrix tablets of domperidone.  

PubMed

Floating matrix tablets of domperidone were developed to prolong gastric residence time and thereby increased drug bioavailability. Domperidone was chosen as a model drug because it is poorly absorbed from the lower gastrointestinal tract. The tablets were prepared by wet granulation technique, using polymers such as hydroxypropylmethylcellulose K4M, carbopol 934P, and sodium alginate, either alone or in combination, and other standard excipients. Tablets were evaluated for physical characteristics viz. hardness, % friability, floating capacity, weight variation and content uniformity. Further, tablets were evaluated for in vitro release characteristics for 24 h. In vitro release mechanism was evaluated by linear regression analysis. Floating matrix tablets based on combination of three polymers namely; hydroxypropylmethylcellulose K4M, carbopol 934P and sodium alginate exhibited desired floating and prolonged drug release for 24 h. Carbopol loading showed negative effect on floating properties but were found helpful to control the release rate of drug. PMID:20177450

Prajapati, S T; Patel, L D; Patel, D M

2009-01-01

4

Studies on Formulation and In Vitro Evaluation of Floating Matrix Tablets of Domperidone  

PubMed Central

Floating matrix tablets of domperidone were developed to prolong gastric residence time and thereby increased drug bioavailability. Domperidone was chosen as a model drug because it is poorly absorbed from the lower gastrointestinal tract. The tablets were prepared by wet granulation technique, using polymers such as hydroxypropylmethylcellulose K4M, carbopol 934P, and sodium alginate, either alone or in combination, and other standard excipients. Tablets were evaluated for physical characteristics viz. hardness, % friability, floating capacity, weight variation and content uniformity. Further, tablets were evaluated for in vitro release characteristics for 24 h. In vitro release mechanism was evaluated by linear regression analysis. Floating matrix tablets based on combination of three polymers namely; hydroxypropylmethylcellulose K4M, carbopol 934P and sodium alginate exhibited desired floating and prolonged drug release for 24 h. Carbopol loading showed negative effect on floating properties but were found helpful to control the release rate of drug.

Prajapati, S. T.; Patel, L. D.; Patel, D. M.

2009-01-01

5

Oral sustained delivery of atenolol from floating matrix tablets-formulation and in vitro evaluation.  

PubMed

Floating matrix tablets of atenolol were developed to prolong gastric residence time and increase drug bioavailability. Atenolol was chosen as a model drug because it is poorly absorbed from the lower gastrointestinal tract. The tablets were prepared by direct compression technique, using polymers such as hydroxypropyl methylcellulose (HPMC K15M, K4M), guargum (GG), and sodium carboxymethylcellulose (SCMC), alone or in combination, and other standard excipients. Tablets were evaluated for physical characteristics viz. hardness, swelling index, floating capacity, thickness, and weight variation. Further, tablets were evaluated for in vitro release characteristics for 8 hr. The effect of effervescent on buoyancy and drug release pattern was also studied. In vitro release mechanism was evaluated by linear regression analysis. GG- and SCMC-based matrix tablets showed significantly greater swelling indices compared with other batches. The tablets exhibited controlled and prolonged drug release profiles while floating over the dissolution medium. PMID:16093202

Srivastava, A K; Wadhwa, Saurabh; Ridhurkar, D; Mishra, B

2005-05-01

6

Optimisation of floating matrix tablets and evaluation of their gastric residence time.  

PubMed

The present investigation concerns the development of the floating matrix tablets, which after oral administration are designed to prolong the gastric residence time, increase the drug bioavailability and diminish the side effects of irritating drugs. The importance of the composition optimisation, the technological process development for the preparation of the floating tablets with a high dose of freely soluble drug and characterisation of those tablets (crushing force, floating properties in vitro and in vivo, drug release) was examined. Tablets containing hydroxypropyl methylcellulose (HPMC), drug and different additives were compressed. The investigation shows that tablet composition and mechanical strength have the greatest influence on the floating properties and drug release. With the incorporation of a gas-generating agent together with microcrystalline cellulose, besides optimum floating (floating lag time, 30 s; duration of floating, >8 h), the drug content was also increased. The drug release from those tablets was sufficiently sustained (more than 8 h) and non-Fickian transport of the drug from tablets was confirmed. Radiological evidence suggests that, that the formulated tablets did not adhere to the stomach mucus and that the mean gastric residence time was prolonged (>4 h). PMID:10675690

Baumgartner, S; Kristl, J; Vrecer, F; Vodopivec, P; Zorko, B

2000-02-15

7

Effect of bioadhesion on initial in vitro buoyancy of effervescent floating matrix tablets of ciprofloxacin HCL.  

PubMed

The purpose of this study was to investigate effect of bioadhesion on the initial in vitro buoyancy behaviour of effervescent matrix tablets of ciprofloxacin HCl (CIPRO). Tablets were prepared by direct compression using HPMC K4M and Carbopol 971P as hydrophilic-controlled release polymers, sodium bicarbonate (NaHCO(3)) as gas-generating agent, polyplasdone XL, Explotab and Ac-Di-Sol as swelling agents. Tablets were evaluated for normal and modified initial in vitro floating behavior, floating duration, swelling behavior and in vitro drug release studies. A modified buoyancy lag time for tablets was determined in order to include the effect of bioadhesion on initial buoyancy. The initial buoyancy was found depended on bioadhesion ability of tablets. The lowest modified buoyancy lag time of 20 seconds was obtained for Formulation F7 having both NaHCO(3) and polyplasdone XL. The floating duration was also found dependent on concentration of NaHCO(3) and swelling agents. The drug release of F7 was also sustained up to 12-hr duration with anomalous drug transport mechanism. PMID:22171304

Negi, Jeetendra Singh; Trivedi, Abhinav; Khanduri, Praveen; Negi, Vandana; Kasliwal, Nikhil

2011-04-01

8

Development and in vitro evaluation of an oral floating matrix tablet formulation of diltiazem hydrochloride.  

PubMed

The purpose of this research was to prepare a floating drug delivery system of diltiazem hydrochloride (DTZ). Floating matrix tablets of DTZ were developed to prolong gastric residence time and increase its bioavailability. Rapid gastrointestinal transit could result in incomplete drug release from the drug delivery system above the absorption zone leading to diminished efficacy of the administered dose. The tablets were prepared by direct compression technique, using polymers such as hydroxypropylmethylcellulose (HPMC, Methocel K100M CR), Compritol 888 ATO, alone or in combination and other standard excipients. Sodium bicarbonate was incorporated as a gas-generating agent. The effects of sodium bicarbonate and succinic acid on drug release profile and floating properties were investigated. A 3(2) factorial design was applied to systematically optimize the drug release profile. The amounts of Methocel K100M CR (X1) and Compritol 888 ATO (X2) were selected as independent variables. The time required for 50% (t50) and 85% (t85) drug dissolution were selected as dependent variables. The results of factorial design indicated that a high level of both Methocel K100M CR (X1) and Compritol 888 ATO (X2) favors the preparation of floating controlled release of DTZ tablets. Comparable release profiles between the commercial product and the designed system were obtained. The linear regression analysis and model fitting showed that all these formulations followed Korsmeyer and Peppas model, which had a higher value of correlation coefficient (r). While tablet hardness had little or no effect on the release kinetics and was found to be a determining factor with regards to the buoyancy of the tablets. PMID:17915823

Gambhire, Manoj N; Ambade, Kshitij W; Kurmi, Sushma D; Kadam, Vilasrao J; Jadhav, Kisan R

2007-01-01

9

Lornoxicam gastro retentive floating matrix tablets: Design and in vitro evaluation  

PubMed Central

The objective of this present investigation is to prolong the gastric residence time of Lornoxicam by fabricating it into a floating sustained release matrix tablets. Lornoxicam, a potent oxicam group of non-steroidal anti-inflammatory drugs, suffers from relatively short half life of 2 to 3 hrs showing maximal absorption in proximal gastro intestinal tract region necessitating its need to be formulated as a floating sustained release matrix tablets. In this current investigation, hydroxyl propyl methyl cellulose K15M, a high viscous grade polymer with apparent viscosity of 15,000 cps, was kept as a variable (10-50%) and calcium carbonate (13%) was used as a gas generator. The prepared blends were subjected for its pre-formulation characterization. The directly compressed tablets were evaluated for physical parameters such as weight uniformity, hardness, friability, drug content, in-vitro buoyancy with axial and radial enlargement measurement, swelling index. From the investigation it was observed that the buoyancy lasted for up to 24 hrs. Fourier transform infra-red spectroscopy peaks assured the compatibility of the drug with excipients and confirmed the presence of pure drug in the formulation. It was supported by in-vitro dissolution studies; and the dissolution data was subjected to various release kinetic models to understand the mechanism of drug release.

Sathiyaraj, S.; Devi, Ramya D.; Hari, Vedha B. N.

2011-01-01

10

Lornoxicam gastro retentive floating matrix tablets: Design and in vitro evaluation.  

PubMed

The objective of this present investigation is to prolong the gastric residence time of Lornoxicam by fabricating it into a floating sustained release matrix tablets. Lornoxicam, a potent oxicam group of non-steroidal anti-inflammatory drugs, suffers from relatively short half life of 2 to 3 hrs showing maximal absorption in proximal gastro intestinal tract region necessitating its need to be formulated as a floating sustained release matrix tablets. In this current investigation, hydroxyl propyl methyl cellulose K15M, a high viscous grade polymer with apparent viscosity of 15,000 cps, was kept as a variable (10-50%) and calcium carbonate (13%) was used as a gas generator. The prepared blends were subjected for its pre-formulation characterization. The directly compressed tablets were evaluated for physical parameters such as weight uniformity, hardness, friability, drug content, in-vitro buoyancy with axial and radial enlargement measurement, swelling index. From the investigation it was observed that the buoyancy lasted for up to 24 hrs. Fourier transform infra-red spectroscopy peaks assured the compatibility of the drug with excipients and confirmed the presence of pure drug in the formulation. It was supported by in-vitro dissolution studies; and the dissolution data was subjected to various release kinetic models to understand the mechanism of drug release. PMID:22171312

Sathiyaraj, S; Devi, Ramya D; Hari, Vedha B N

2011-07-01

11

Floating matrix tablets of domperidone formulation and optimization using simplex lattice design.  

PubMed

The purpose of this research was to prepare a floating matrix tablet containing domperidone as a model drug. Polyethylene oxide (PEO) and hydroxypropyl methylcellulose (HPMC) were evaluated for matrix-forming properties. A simplex lattice design was applied to systemically optimize the drug release profile. The amounts of PEO WSR 303, HPMC K15M and sodium bicarbonate were selected as independent variables and floating lag time, time required to release 50% of drug (t50) and 80% of drug (t80), diffusion coefficient (n) and release rate (k) as dependent variables. The amount of PEO and HPMC both had significant influence on the dependent variables. It was found that the content of PEO had dominating role as drug release controlling factor, but using suitable concentration of sodium bicarbonate, one can tailor the desired drug release from hydrophilic matrixes. The linear regression analysis and model fitting showed that all these formulations followed Korsmeyer and Peppas model, which had a higher value of correlation coefficient (r). The tablets of promising formulation were found to be stable for 3 months under accelerated (40°C / 75% RH) stability testing. PMID:24250376

Prajapati, Shailesh; Patel, Laxmanbhai; Patel, Chhaganbhai

2011-01-01

12

Floating Matrix Tablets of Domperidone Formulation and Optimization Using Simplex Lattice Design  

PubMed Central

The purpose of this research was to prepare a floating matrix tablet containing domperidone as a model drug. Polyethylene oxide (PEO) and hydroxypropyl methylcellulose (HPMC) were evaluated for matrix-forming properties. A simplex lattice design was applied to systemically optimize the drug release profile. The amounts of PEO WSR 303, HPMC K15M and sodium bicarbonate were selected as independent variables and floating lag time, time required to release 50% of drug (t50) and 80% of drug (t80), diffusion coefficient (n) and release rate (k) as dependent variables. The amount of PEO and HPMC both had significant influence on the dependent variables. It was found that the content of PEO had dominating role as drug release controlling factor, but using suitable concentration of sodium bicarbonate, one can tailor the desired drug release from hydrophilic matrixes. The linear regression analysis and model fitting showed that all these formulations followed Korsmeyer and Peppas model, which had a higher value of correlation coefficient (r). The tablets of promising formulation were found to be stable for 3 months under accelerated (40°C / 75% RH) stability testing.

Prajapati, Shailesh; Patel, Laxmanbhai; Patel, Chhaganbhai

2011-01-01

13

Effect of sodium bicarbonate on the properties of metronidazole floating matrix tablets.  

PubMed

The effect of sodium bicarbonate (SB) on the swelling behavior and the sustained release of floating systems was studied with varied proportions of this excipient and metronidazole. Two polymers with different hydration characteristics, Methocel K4M and Carbopol 971P NF, were used to formulate the matrices. Under in vitro dissolution conditions, the addition of SB to metronidazole sustained-release tablets modifies the matrix hydration volume, increasing at the beginning, reaching a maximum, and then declining. Pure Carbopol matrices show a rapid hydration with a limited further effect of the SB and metronidazole loads. Methocel show a significant increase of the apparent hydration volume due to SB addition with no further notable change due to metronidazole load. Increasing the metronidazole load reduces the floating time of Carbopol matrices while no effect on Methocel matrices could be observed within 8 hours dissolution. Matrices show increasing release constant values (k) as the metronidazole load increases. Methocel matrices release the drug 10% to 15% faster than Carbopol matrices. SB increases the cumulative amount of drug released from Methocel but not that releasing from Carbopol. These results are attributed to the intrinsic polymer properties, the barrier effect of CO(2) bubbles, and the matrix volume expansion produced after addition of SB. PMID:18302036

Gutiérrez-Sánchez, Pablo Emilio; Hernández-León, Alejandra; Villafuerte-Robles, Leopoldo

2008-02-01

14

Preparation and evaluation of novel metronidazole sustained release and floating matrix tablets.  

PubMed

In the present study, metronidazole was used for preparing floating dosage forms that are designed to retain in the stomach for a long time and have developed as a drug delivery system for better eradication of Helicobacter Pylori in peptic ulcer diseases. For this means, various formulations were designed using multi-factorial design. HPMC, psyllium and carbopol in different concentrations were used as floating agents, and sodium bicarbonate was added as a gas-forming agent. Hardness, friability, drug loading, floating ability and release profiles as well as kinetics of release were assessed. Formulations containing HPMC as filler showed prolonged lag times for buoyancy. Adding psyllium to these formulations had reduced relative lag times. Overall, selected formulations were able to float immediately and showed buoyancy for at least 8?h. Meanwhile, sustained profiles of drug release were also obtained. Kinetically, among the 10 assessed models, the release pattern of metronidazole from the tablets fitted best to Power law, Weibull and Higuchi models in respect overall to mean percentage error values of 3.8, 4.73 and 5.77, respectively, for calcium carbonate-based tablets and, 2.95, 6.39 and 3.9, respectively, for calcium silicate-based tablets. In general, these systems can float in the gastric condition and control the drug release from the tablets. PMID:20429828

Asnaashari, Solmaz; Khoei, Nazaninossadat Seyed; Zarrintan, Mohammad Hosein; Adibkia, Khosro; Javadzadeh, Yousef

2011-08-01

15

Polymers derived from Xanthomonas campesteris and Cyamopsis tetragonolobus used as retardant materials for the formulation of sustained release floating matrix tablet of atenolol.  

PubMed

The objective of the present study was to develop, optimize, in vitro, and in vivo evaluation of floating matrix tablet of atenolol using polymer blend derived from Xanthomonas campesteris and Cyamopsis tetragonolobus that are characterized by release requirements of sustained-release product and to improve the oral bioavailability of the drug. A 3(2) full factorial design was employed to optimize the tablets, where content of polymer blend (X1) and ratio of xanthan gum-to-guar gum (X2) were considered as independent variables. The effects of independent variables on dependent variables, i.e. floating time, diffusion exponent, and time to release 50% of atenolol were evaluated. The in vivo pharmacokinetic parameters of the optimized formulation were compared with the marketed sustained release formulation of atenolol (Aten(®)). The optimized formulation containing 20% (w/w) of polymer blend and 50:50 ratio of xanthan gum-to-guar gum was able to float more than 12h and showed the desired sustained drug release from the tablets. In vivo retention studies in rabbit stomach showed the gastric residence of tablet up to 6h. The in vivo study of optimized tablets illustrated significant improvement in the oral bioavailability of atenolol in rabbits. It can be concluded that floating matrix tablet of atenolol prepared by using xanthan gum and guar gum has potential for sustained release of the drug as well as improved oral bioavailability through enhanced gastric residence time of formulation in stomach. PMID:24472506

Dey, Sanjay; Mazumder, Bhaskar; Chattopadhyay, Sankha; Das, Malay Kanti; Sinha, Samarendu; Ganguly, Shantanu; De, Kakali; Mishra, Mridula

2014-04-01

16

Floating and sustained-release characteristics of effervescent tablets prepared with a mixed matrix of Eudragit L-100-55 and Eudragit E PO.  

PubMed

The aim of this study was to evaluate the influence of Na-bicarbonate as an effervescent agent on the floating and sustained-release characteristics in 0.1 M HCl of tablets made of Eudragit E PO (EE) and/or Eudragit L-100-55 (EL) as matrix formers at different EE:EL weight ratios: 0:100, 25:75, 50:50, 75:25, and 100:0. The tablets were made by direct compression utilizing metronidazole as a model drug. Effervescent tablets with 50EE/50EL (w/w) showed the best floating and sustained drug release properties in the dissolution medium. The corresponding noneffervescent tablets were nonfloating and showed significantly faster drug release. Effervescent tablets with single polymers showed an immediate drug release pattern. These results were explained by Fourier-transform infrared spectroscopy and elemental analysis, which showed strong evidence of interpolyelectrolyte complexation between EE and EL when they were exposed to 0.1 M HCl as an effervescent hybrid matrix, but not as a noneffervescent hybrid matrix. The role of Na-bicarbonate in allowing EE-EL complexation during dissolution was explained as due to raising the pH around EL particles for sufficient polymer ionization and ionic-interaction with the ionized EE. PMID:21297292

Bani-Jaber, Ahmad Khaled; Alkawareek, Mahmoud Yousef; Al-Gousous, Jozef Jawad; Abu Helwa, Ahmad Yousef

2011-01-01

17

Gastric floating matrix tablets: design and optimization using combination of polymers.  

PubMed

The purpose of the present study was to develop an optimized gastric floating drug delivery system (GFDDS) containing domperidone as a model drug. Box-Behnken design was employed in formulating the GFDDS with three polymers: hydroxypropyl methylcellulose K4M (HPMC K4M) (X1), Carbopol 934P (X2) and sodium alginate (X3), as independent variables. Floating lag time (FLT), total floating time (TFT), time required to release 50% of the drug (t50) and diffusion exponent (n) were selected as dependent variables. Seventeen formulations were prepared, dissolution data obtained was fitted to the power law and floating profiles were analyzed. HPMC loading was found to be significant for floating properties. Carbopol loading had a negative effect on floating properties but was found helpful in controlling the release rate of the drug. No significant effect of sodium alginate on floating properties was observed but it was important for gel formation. The quadratic mathematical model developed could be used to predict formulations with desired release and floating properties. PMID:18515232

Prajapati, Shailesh T; Patel, Laxmanbhai D; Patel, Dasharath M

2008-06-01

18

Preparation and evaluation of gastroretentive floating tablets of acyclovir.  

PubMed

The present study performed by preparation and evaluation of floating tablets of Acyclovir as model drug for prolongation of gastric residence time. Floating effervescent tablets were formulated by various materials like hydroxypropyl methylcellulose K 4M, K 15M, psyllium husk, swelling agent as crospovidone and microcrystalline cellulose and gas generating agent like sodium bicarbonate and citric acid and evaluated for floating properties, swelling characteristics and in vitro drug release studies. Floating noneffervescent tablets were prepared by polypropylene foam powder and different matrix forming polymers like HPMC K 4M, Carbopol 934P, xanthan gum and sodium alginate. In vitro drug release studies were performed and drug release kinetics evaluated using the linear regression method was found to follow both the Higuchi and the Korsmeyer and Peppas equation. The drug release mechanism was found fickian type in most of the formulations. PMID:19751200

Garg, Rajeev; Gupta, G D

2009-10-01

19

Statistical evaluation of influence of xanthan gum and guar gum blends on dipyridamole release from floating matrix tablets.  

PubMed

The present investigation explored the use of xanthan gum and guar gum for development of floating drug delivery system of dipyridamole using factorial design approach. The content of polymer blends (X(1)) and ratio of xanthan gum to guar gum (X(2)) were selected as independent variables. The diffusion exponent (n), release rate constant (k), percentage drug release at 1 hr (Q(1)) and 6 hr (Q(6)) were selected as dependent variables. Tablets of all batches had desired buoyancy characteristics. Multiple regression analysis with two way ANOVA revealed that both the factors had statistically significant influence on the response studied (p<0.05). Results of Tukey test showed the relative contribution of each level of different factors for the response studied. It was concluded that the ratio of xanthan to gaur gum had equal or dominant role as controlling factor on kinetics of drug release compared to content of polymer blends. PMID:17454065

Patel, Viral F; Patel, Natavarlal M

2007-03-01

20

Preparation and evaluation of gastroretentive floating tablets of Silymarin.  

PubMed

The present study performed by preparation and evaluation of floating tablets of Silymarin as model drug for prolongation of gastric residence time. Floating effervescent tablets were formulated by various materials like hydroxypropyl methylcellulose (HPMC) K 4M, K 15M, psyllium husk, swelling agent as crospovidone and microcrystalline cellulose and gas generating agent like sodium bicarbonate and citric acid and evaluated for floating properties, swelling characteristics and in vitro drug release studies. Floating noneffervescent tablets were prepared by polypropylene foam powder and different matrix forming polymers like HPMC K 4M, Carbopol 934P, xanthan gum and sodium alginate. In vitro drug release studies were performed and drug release kinetics evaluated using the linear regression method was found to follow both the Higuchi and the Korsemeyer and Peppas equation. The drug release mechanism was found fickian type in most of the formulations. The developed floating tablets of Silymarin may be used in clinic for prolonged drug release for at least 24 h, thereby improving the bioavailability and patient compliance. PMID:19483331

Garg, Rajeev; Gupta, Ghanshyam Das

2009-06-01

21

Floating Tablet of Trimetazidine Dihydrochloride: An Approach for Extended Release with Zero-Order Kinetics  

PubMed Central

Trimetazidine dihydrochloride is an effective anti-anginal agent; however, it is freely soluble in water and suffers from a relatively short half-life. To solve this encumbrance, it is a prospective candidate for fabricating trimetazidine extended-release formulations. Trimetazidine extended-release floating tablets were prepared using different hydrophilic matrix forming polymers including HPMC 4000 cps, carbopol 971P, polycarbophil, and guar gum. The tablets were fabricated by dry coating technique. In vitro evaluation of the prepared tablets was performed by the determination of the hardness, friability, content uniformity, and weight variation. The floating lag time and floating duration were also evaluated. Release profile of the prepared tablets was performed and analyzed. Furthermore, a stability study of the floating tablets was carried out at three different temperatures over 12 weeks. Finally, in vivo bioavailability study was done on human volunteers. All tablet formulas achieved <0.5 min of floating lag time, more than 12 h of floating duration, and extended t1/2. The drug release in all formulas followed zero-order kinetics. T4 and T8 tablets contained the least polymer concentration and complied with the dissolution requirements for controlled-release dosage forms. These two formulas were selected for further stability studies. T8 exhibited longer expiration date and was chosen for in vivo studies. T8 floating tablets showed an improvement in the drug bioavailability compared to immediate-release tablets (Vastrel® 20 mg).

Abdelbary, Ahmed; El-Gazayerly, Omaima N.; Ali, Adel A.

2010-01-01

22

Formulation and evaluation of non-effervescent floating tablets of losartan potassium.  

PubMed

The aim of the work is to modify the solubility and bioavailability of Losartan potassium, by employing noneffervescent floating drug delivery (tablet dosage forms). Non-effervescent systems are a type of floating drug delivery systems, that have been used to boost the gastric residence and the floatation time in the gastro intestinal tract. The study included formulation of floating tablets using polymers like Chitosan and Karaya gum as matrix forming agents. Accurel(®) MP 1000 was used as floating agent. The tablets were prepared by direct compression technique. FTIR, DSC studies conformed that there was no incompatibility between the polymer and the drug. Tablet preformulation parameters were within the Pharmacopoeial limit. Tablet showed zero lag time, contisnuance of buoyancy for >12 h. The tablet showed good in vitro release. Drug release was through swelling and abided by the gellation mechanism. In vivo X-ray studies depicted that tablets continued to float in the GIT for 12 h. Accelerated stability showed that, tablets were stable for over 6 month. Thus the prepared non-effervescent floating tablet of Losartan potassium can be used for the treatment of hypertension for more than 12 h with single dose administration. PMID:23286884

Getyala, Anil; Gangadharappa, H V; Prasad, M Sarat Chandra; Reddy, M Praveen Kumar; Kumar, T M Pramod

2013-10-01

23

Design of floating bilayer tablets of diltiazem hydrochloride and lovastatin.  

PubMed

The purpose of the study is to design bilayer floating tablets of diltiazem HCI and lovastatin to give immediate release of lovastatin and controlled release of diltiazem HCl and to study the influence of presence of one drug on the release pattern of other drug. The bilayer tablets consist of sodium starch glycolate as superdisintegrant for lovastatin in the immediate release layer and hydroxypropyl methylcellulose (HPMC) K4M and Xanthan gum as release-retarding agents for diltiazem HCl in the controlled release layer. Sodium bicarbonate was used as the gas generating agent. Dicalcium phosphate was used as the channeling agent. The direct compression method was employed for preparation of the bilayer tablets. Various physicochemical parameters were evaluated for the prepared tablets. The physicochemical parameters were found to be within range. There was significant difference in drug release and floating lag time (P < 0.05). All the formulations showed good matrix integrity. All the formulations released lovastatin within 30 min. The diffusion exponent for diltiazem HCl was found to be independent of polymer concentration. The release pattern of diltiazem HCI was fitted to different models based on coefficient of correlation (R). All the formulations followed the Higuchi model, except F1 which followed the Peppas model. HPMC K4M and Xanthan gum retarded the release of diltiazem HCl for 12 h. The release of one drug remained unaffected in presence of the other drug. In conclusion, such kind of combined dosage forms can effectively be formulated to deliver more than one drug so as to have improved patient compliance and better disease management. PMID:19055230

Kulkarni, Ajit S; Bhatia, Manish S

2008-01-01

24

Formulation and evaluation of floating tablets of liquorice extract  

PubMed Central

Background: Floating tablets prolong the gastric residence time of drugs, improve bioavailability, and facilitate local drug delivery to the stomach. With this objective, floating tablets containing aqueous extract of liquorice as drug was prepared for the treatment of Helicobacter pylori and gastric ulcers. Methods: The aqueous extract of liquorice was standardized by HPTLC. Tablets containing HPMC K100M (hydrophilic polymer), liquorice extract, sodium bicarbonate (gas generating agent), talc, and magnesium stearate were prepared using direct compression method. The formulations were evaluated for physical parameters like diameter, thickness, hardness, friability, uniformity of weight, drug content, buoyancy time, dissolution, and drug release mechanism. The formulations were optimized on the basis of buoyancy time and in vitro drug release. Results: The diameter of all formulations was in the range 11.166–11.933 mm; thickness was in the range 4.02–4.086 mm. The hardness ranged from 3.1 to 3.5 kg/cm2. All formulations passed the USP requirements for friability and uniformity of weight. The buoyancy time of all tablet formulations was less than 5 min and tablet remained in floating condition throughout the study. All the tablet formulations followed zero-order kinetics and Korsemeyer-Peppas model in drug release. Conclusion: The optimized formulation was found to be F6 which released 98.3% of drug in 8 h in vitro, while the buoyancy time was 3.5 min. Formulations containing psyllium husk, sodium bicarbonate and HPMC K100M in combination can be a promising for gastroretentive drug delivery systems.

Ram, H. N. Aswatha; Lachake, Prachiti; Kaushik, Ujjwal; Shreedhara, C. S.

2010-01-01

25

Development and in vivo floating behavior of verapamil HCl intragastric floating tablets.  

PubMed

A novel gastro retentive controlled release drug delivery system of verapamil HCl was formulated in an effort to increase the gastric retention time of the dosage form and to control drug release. Hydroxypropylmethylcellulose (HPMC), carbopol, and xanthan gum were incorporated for gel-forming properties. Buoyancy was achieved by adding an effervescent mixture of sodium bicarbonate and anhydrous citric acid. In vitro drug release studies were performed, and drug release kinetics was evaluated using the linear regression method. The optimized intragastric floating tablet composed of 3:2 of HPMC K4M to xanthan gum exhibited 95.39% drug release in 24 h in vitro, while the buoyancy lag time was 36.2 s, and the intragastric floating tablet remained buoyant for >24 h. Zero-order and non-Fickian release transport was confirmed as the drug release mechanism from the optimized formulation (F7). X-ray studies showed that total buoyancy time was able to delay the gastric emptying of verapamil HCl intragastric floating tablet in mongrel dogs for more than 4 h. Optimized intragastric floating tablet showed no significant change in physical appearance, drug content, total buoyancy time, or in vitro dissolution pattern after storage at 40 degrees C/75% relative humidity for 3 months. PMID:19296224

Patel, Anand; Modasiya, Moin; Shah, Dushyant; Patel, Vishnu

2009-01-01

26

Design, development and evaluation of clopidogrel bisulfate floating tablets  

PubMed Central

Objective: The objective of the present work was to formulate and to characterize a floating drug delivery system for clopidogrel bisulphate to improve bioavailability and to minimize the side effects of the drug such as gastric bleeding and drug resistance development. Materials and Methods: Clopidogrel floating tablets were prepared by direct compression technique by the use of three polymers xanthan gum, hydroxypropyl methylcellulose (HPMC) K15M and HPMC K4M in different concentrations (20%, 25% and 30% w/w). Sodium bicarbonate (15% w/w) and microcrystalline cellulose (30% w/w) were used as gas generating agent and diluent respectively. Studies were carried out on floating behavior and influence of type of polymer on drug release rate. All the formulations were subjected to various quality control and in-vitro dissolution studies in 0.1 N hydrochloric acid (1.2 pH) and corresponding dissolution data were fitted to popular release kinetic equations in order to evaluate release mechanisms and kinetics. Results and Discussion: All the clopidogrel floating formulations followed first order kinetics, Higuchi drug release kinetics with diffusion as the dominant mechanism of drug release. As per Korsmeyer-Peppas equation, the release exponent “n” ranged 0.452-0.654 indicating that drug release from all the formulations was by non-Fickian diffusion mechanism. The drug release rate of clopidogrel was found to be affected by the type and concentration of the polymer used in the formulation (P < 0.05). As the concentration of the polymer was increased, the drug release was found to be retarded. Conclusion: Based on the results, clopidogrel floating tablets prepared by employing xanthan gum at concentration 25% w/w (formulation F2) was the best formulation with desired in-vitro floating time and drug dissolution.

Rao, K. Rama Koteswara; Lakshmi, K. Rajya

2014-01-01

27

Development of bilayer floating tablet of amoxicillin and Aloe vera gel powder for treatment of gastric ulcers.  

PubMed

Usual treatment for Helicobacter pylori-induced peptic ulcer includes a 'triple therapy' consisting of two antibiotics (amoxicillin and clarithromycin) and a proton pump inhibitor (omeprazole). The objective of this project work was defined with a view to retain the drug in stomach for better antiulcer activity and substituting one of the synthetic drugs in this therapy with a herbal alternative. Hence, aim of the present work was to design and develop a bilayer floating tablet of amoxicillin and Aloe vera gel powder for the treatment of peptic ulcer. A. vera gel powder is used for its cytoprotective action. Bilayer floating tablets were prepared by applying direct compression technique. The proportion of sodium bicarbonate and citric acid was adjusted to get the least possible lag time with good matrix integrity and total floating time. Polymer concentration was adjusted to get the maximum release in 8 h. The formulation was developed using hydroxypropyl methyl cellulose (HPMC) K4M and HPMC K100M in a ratio of 85:15 along with 1:4 ratio of effervescent agents was found to give floating lag time of less than 1 min with total floating time of more than 8 h and 97.0% drug release in 8 h. In vivo study in rats meets the requirement of antiulcer activity for bilayer tablet in comparison to single amoxicillin as standard. PMID:23135966

Ranade, Arati N; Wankhede, Sonali S; Ranpise, Nisharani S; Mundada, Mayur S

2012-12-01

28

Design and characterization of controlled release gastro-retentive floating tablet of an atypical psychotropic agent  

PubMed Central

The purpose of the present work was to design and evaluate the once daily sustained release matrix type gastro-retentive floating tablet of Quetiapine Fumarate base on hydrophilic matrices of HPMC, sodium CMC and Carbopol. Sodium bicarbonate was incorporated as a gas-generating agent to give buoyancy. In-vitro drug release studies were performed in pH 1.2 buffer using USP type II paddle at 50 rpm. The release rate of drug decreased with increasing polymer proportion of HPMC K15M from 20 to 60 mg. Formulation with desired drug release achieved with combination of sodium CMC and K15M in ratio of 1:3. The drug release mechanism was predominantly found to be Non-Fickian diffusion and Higuchi controlled.

Ukawala, Ravikumar; Singhvi, Gautam; Jain, Suresh; Shukla, Vipin; Yadav, Nilesh; Sharma, Sohiny

2012-01-01

29

Prolonged intragastric drug delivery mediated by Eudragit® E-carrageenan polyelectrolyte matrix tablets.  

PubMed

Interpolyelectrolyte (IPE) complexation between carrageenan (CG) and Eudragit E (EE) was studied in 0.1 M HCl and was used to develop floating matrix tablets aimed to prolong gastric-residence time and sustain delivery of the loaded drug. The optimum EE/CG IPE complexation weight ratio (0.6) was determined in 0.1 M HCl using apparent viscosity measurements. The IPE complex was characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. Metronidazole matrix tablets were prepared by direct compression using EE, CG, or hybrid EE/CG with ratio optimal for IPE complexation. Corresponding effervescent tablets were prepared by including Na bicarbonate as an effervescent agent. Tablets were evaluated for in vitro buoyancy and drug release in 0.1 M HCl. Both CG and EE-CG effervescent matrices (1:2 drug to polymer weight ratio, 60 mg Na bicarbonate) achieved fast and prolonged floating with floating lag times less than 30 s and floating duration of more than 10 h. The corresponding EE effervescent matrices showed delayed floating and rapid drug release, and completely dissolved after 3 h of dissolution. CG matrices showed an initial burst drug release (48.3±5.0% at 1 h) followed by slow drug release over 8 h. EE-CG matrices exhibited sustained drug release in almost zero-order manner for 10 h (68.2±6.6%). The dissolution data of these matrices were fitted to different dissolution models. It was found that drug release followed zero-order kinetics and was controlled by the superposition of the diffusion and erosion. PMID:21302009

Bani-Jaber, Ahmad; Al-Aani, Leena; Alkhatib, Hatim; Al-Khalidi, Bashar

2011-03-01

30

Release Mechanisms Behind Polysaccharides-Based Famotidine Controlled Release Matrix Tablets  

PubMed Central

Polysaccharides, which have been explored to possess gelling properties and a wide margin of safety, were used to formulate single-unit floating matrix tablets by a direct compression technique. This work has the aim to allow continuous slow release of famotidine above its site of absorption. The floating approach was achieved by the use of the low density polypropylene foam powder. Polysaccharides (?-carrageenan, gellan gum, xyloglucan, and pectin) and blends of polysaccharides (?-carrageenan and gellan gum) and cellulose ethers (hydroxypropylmethyl cellulose, hydroxypropylcellulose, sodium carboxymethyl cellulose) were tried to modulate the release characteristics. The prepared floating tablets were evaluated for their floating behavior, matrix integrity, swelling studies, in vitro drug release studies, and kinetic analysis of the release data. The differential scanning calorimetry and Fourier transform infrared spectroscopy studies revealed that changing the polymer matrix system by formulation of polymers blends resulted in formation of molecular interactions which may have implications on drug release characteristics. This was obvious from the retardation in drug release and change in its mechanistics.

Elmowafy, Enas M.; Awad, Gehanne A. S.; El-Shamy, Abd El-Hamid A.

2008-01-01

31

Release mechanisms behind polysaccharides-based famotidine controlled release matrix tablets.  

PubMed

Polysaccharides, which have been explored to possess gelling properties and a wide margin of safety, were used to formulate single-unit floating matrix tablets by a direct compression technique. This work has the aim to allow continuous slow release of famotidine above its site of absorption. The floating approach was achieved by the use of the low density polypropylene foam powder. Polysaccharides (kappa-carrageenan, gellan gum, xyloglucan, and pectin) and blends of polysaccharides (kappa-carrageenan and gellan gum) and cellulose ethers (hydroxypropylmethyl cellulose, hydroxypropylcellulose, sodium carboxymethyl cellulose) were tried to modulate the release characteristics. The prepared floating tablets were evaluated for their floating behavior, matrix integrity, swelling studies, in vitro drug release studies, and kinetic analysis of the release data. The differential scanning calorimetry and Fourier transform infrared spectroscopy studies revealed that changing the polymer matrix system by formulation of polymers blends resulted in formation of molecular interactions which may have implications on drug release characteristics. This was obvious from the retardation in drug release and change in its mechanistics. PMID:19089643

Elmowafy, Enas M; Awad, Gehanne A S; Mansour, Samar; El-Shamy, Abd El-Hamid A

2008-01-01

32

Floating-point sparse matrix-vector multiply for FPGAs  

Microsoft Academic Search

Large, high density FPGAs with high local distributed memory bandwidth surpass the peak floating-point performance of high-end, general-purpose processors. Microprocessors do not deliver near their peak floating-point performance on efficient algorithms that use the Sparse Matrix-Vector Multiply (SMVM) kernel. In fact, it is not uncommon for microprocessors to yield only 10--20% of their peak floating-point performance when computing SMVM. We

Michael deLorimier; André DeHon

2005-01-01

33

Floating matrix dosage form for phenoporlamine hydrochloride based on gas forming agent: in vitro and in vivo evaluation in healthy volunteers.  

PubMed

Phenoporlamine hydrochloride is a novel compound that is used for the treatment of hypertension. The purpose of this study was to develop a sustained release tablet for phenoporlamine hydrochloride because of its short biological half-life. Three floating matrix formulations of phenoporlamine hydrochloride based on gas forming agent were prepared. Hydroxypropyl methylcellulose K4M and Carbopol 971P NF were used in formulating the hydrogel drug delivery system. Incorporation sodium bicarbonate into matrix resulted in the tablet floating over simulated gastric fluid for more than 6h. The dissolution profiles of all tablets showed non-Fickian diffusion in simulated gastric fluid. Moreover, release of the drug from these tablets was pH-dependent. In vivo evaluations of these formulations of phenoporlamine hydrochloride were conducted in six healthy male human volunteers to compare the sustained release tablets with immediate release tablets. Data obtained in these studies demonstrated that the floating matrix tablet containing more Carbopol was capable of sustained delivery of the drug for longer periods with increased bioavailability and the relative bioavailability of formulation (containing 25% Carbopol 971P NF, 8.3% HPMC K4M) showed the best bioequivalency to the reference tablet (the relative bioavailability was 1.11+/-0.19). PMID:16413710

Xu, Xiaoqiang; Sun, Minjie; Zhi, Feng; Hu, Yiqiao

2006-03-01

34

Study of drug release and tablet characteristics of silicone adhesive matrix tablets.  

PubMed

Matrix tablets of a model drug acetaminophen (APAP) were prepared using a highly compressible low glass transition temperature (T(g)) polymer silicone pressure sensitive adhesive (PSA) at various binary mixtures of silicone PSA/APAP ratios. Matrix tablets of a rigid high T(g) matrix forming polymer ethyl cellulose (EC) were the reference for comparison. Drug release study was carried out using USP Apparatus 1 (basket), and the relationship between the release kinetic parameters of APAP and polymer/APAP ratio was determined to estimate the excipient percolation threshold. The critical points attributed to both silicone PSA and EC tablet percolation thresholds were found to be between 2.5% and 5% w/w. For silicone PSA tablets, satisfactory mechanical properties were obtained above the polymer percolation threshold; no cracking or chipping of the tablet was observed above this threshold. Rigid EC APAP tablets showed low tensile strength and high friability. These results suggest that silicone PSA could eliminate issues related to drug compressibility in the formulation of directly compressed oral controlled release tablets of poorly compressible drug powder such as APAP. No routinely used excipients such as binders, granulating agents, glidants, or lubricants were required for making an acceptable tablet matrix of APAP using silicone PSA. PMID:22820648

Tolia, Gaurav; Li, S Kevin

2012-11-01

35

64-bit floating-point FPGA matrix multiplication  

Microsoft Academic Search

We introduce a 64-bit ANSI\\/IEEE Std 754-1985 floating point design of a hardware matrix multiplier optimized for FPGA implementations. A general block matrix multiplication algorithm, applicable for an arbitrary matrix size is proposed. The algorithm potentially enables optimum performance by exploiting the data locality and reusability incurred by the general matrix multiplication scheme and considering the limitations of the I\\/O

Yong Dou; Stamatis Vassiliadis; Georgi Kuzmanov; G. N. Gaydadjiev

2005-01-01

36

Formulation, release characteristics and bioavailability of novel monolithic hydroxypropylmethylcellulose matrix tablets containing acetaminophen  

Microsoft Academic Search

Effect of incorporating pharmaceutical excipients on the in vitro release profiles and the release mechanism of monolithic hydroxypropylmethylcellulose (4000 cps) matrix tablets (m-HPMC tablets) in terms of mimicking the dual drug release character of bi-layered Tylenol® ER tablets was studied. We also compared the in vitro release profiles of optimized m-HPMC matrix tablet and Tylenol® ER tablet in water, pH

Qing-Ri Cao; Yun-Woong Choi; Jing-Hao Cui; Beom-Jin Lee

2005-01-01

37

The effect of chemical heterogeneity of HPMC on polymer release from matrix tablets  

Microsoft Academic Search

Polymer release from hydrophilic matrix tablets, composed of hydroxypropyl methylcellulose, was studied for seven different polymer batches. A time difference of more than 80h between fully dissolved tablets was noticed although the batches were of the same pharmaceutical substituent (USP 2208) and viscosity (100 cps) grade. To find the functionality related parameters for polymer release from hydrophilic matrix tablets the

Anna Viridén; Bengt Wittgren; Thomas Andersson; Anette Larsson

2009-01-01

38

Influence of water-soluble polymers on the in vitro performance of floating mucoadhesive tablets containing metformin.  

PubMed

Abstract Context: The in vitro performance of floating mucoadhesive metformin tablets was optimized using different polymer ratios of polyvinylpyrrolidone (PVP) tamarind seed gum (TSG) and hydroxypropylmethylcellulose (HPMC). Objective: The objectives of this investigation were to investigate the combinatorial effects of PVP, TSG and HPMC; to study the work of adhesion measured on stainless steel (Wss) and on rabbit gastric mucosa (Wgm); and a comparison of hydrophilic and more hydrophobic tablets. Material and methods: In vitro performance was measured as tablet hardness (H), tablet floating lag time (FLT), time needed to release 60% of drug content (t60%), swelling thickness (S), Wss and Wgm. To compare the effects, a simplex lattice mixture design was used. Results and discussion: H, FLT, Wss and Wgm were found dependent on polymer ratio. H was increased when PVP ratio was increased. FLT, Wss and Wgm were increased when HPMC ratio was increased. The p value for the lack of fit for all models were greater than 0.05. An approximate linear correlation between Wgm and Wss was established (R(2)?=?0.71). The tablets containing PVP resulted in larger H, shorter FLT and t60%, whereas Wss and Wgm were enhanced. Conclusion: The different in vitro performance of tablets containing different water-soluble polymers could be explained partially by the differences in the hydrophilic properties of the polymers and the ability of PVP to interact with HPMC or TSG. An equation established is used to conclude mucoadhesion based on adhesion measurements on stainless steel. PMID:23607725

Rajab, Mazen; Jouma, Muhidien; Neubert, Reinhard H H; Dittgen, Michael

2014-07-01

39

Optimization of HPMC and carbopol concentrations in non-effervescent floating tablet through factorial design.  

PubMed

This study was to optimize HPMC K4M and carbopol 934 concentration in the development of non-effervescent floating tablets (NEFTs) of glipizide as model drug using 3(2) factorial design. The time required for releasing drug of 50% and 80% and similarity factor were the target responses. HPMC K4M and carbopol 934 concentrations were the variables. The response surface methodology and optimized polynomial equations were used to select the optimal formulation with desired responses. The excipients used in tablets were compatible with glipizide as per the results of isothermal stress testing and DSC study. The drug release of entire NEFTs followed zero order kinetics and non-Fickian diffusion mechanism. Validation of the optimization technique demonstrated the reliability of the model. The optimized formulation containing 124.33 mg HPMC K4M and 25.76 mg carbopol 934 was prepared according to the software determined levels. The stability study of the optimized formulation proved the integrity of the developed formulation. PMID:24507292

Acharya, Sujata; Patra, Sradhanjali; Pani, Nihar Ranjan

2014-02-15

40

Modeling drug release from PVAc/PVP matrix tablets.  

PubMed

Kollidon SR-based matrix tablets containing various amounts of diprophylline were prepared and thoroughly characterized in vitro. This includes drug release measurements in 0.1M HCl and phosphate buffer pH 7.4, monitoring of changes in the tablet's height and diameter, morphology as well as dry mass upon exposure to the release media. Based on these experimental results, a mechanistic realistic mathematical theory is proposed, taking into account the given initial and boundary conditions as well as radial and axial mass transport in cylinders. Importantly, good agreement between theory and experiment was obtained in all cases, indicating that drug diffusion with constant diffusivity is the dominant mass transport mechanism in these systems. Furthermore, the proposed theory was used to quantitatively predict the effects of the initial tablet height and diameter on the resulting drug release patterns. These theoretical predictions were compared with independently measured drug release kinetics. Good agreement was observed in all cases, proving the validity of the mathematical theory and illustrating the latter's practical benefit: The model can help to significantly facilitate the recipe optimization of this type of advanced drug delivery systems in order to achieve a desired release profile. PMID:19737588

Siepmann, F; Eckart, K; Maschke, A; Kolter, K; Siepmann, J

2010-01-25

41

Floating matrix dosage form for dextromethorphan hydrobromide based on gas forming technique: in vitro and in vivo evaluation in healthy volunteers.  

PubMed

The objective of this study was to develop the dextromethorphan hydrobromide sustained-release (DMB-SR) tablets using floating technique to prolong the gastric residence time and compared their pharmacokinetic behavior with conventional sustained release tablets. DMB-SR floating tablets were prepared employing hydroxypropyl methylcellulose (HPMC) as hydrophilic gel material, sodium bicarbonate as gas-generating agent and hexadecanol as floating assistant agent. An orthogonal experiment design method was used to select the optimized formulation. The floating tablets were evaluated for uniformity of weight, hardness, friability, drug content, floating characteristics, in vitro release and in vivo bioavailability. The optimized tablets were prepared with HPMC K4M 25 mg, sodium bicarbonate 20 mg and hexadecanol 18 mg. The prepared tablets could float within 3 min and maintain for more than 24 h. The data of physical parameters were all lie within the limits. Drug release at 12 h was more than 85%. The comparative pharmacokinetic study was performed by administration of the DMB-SR floating tablets and conventional DMB-SR tablets. The area under curve of plasma concentration-time (AUC) of floating tablets was slightly higher than that of reference tablets, T(max) was prolonged apparently. The results showed the floating tablets are a feasible approach for the sustained-release preparation of drugs, which have limited absorption sites in the stomach. PMID:21050887

Hu, Liandong; Li, Li; Yang, Xun; Liu, Wei; Yang, Jianxue; Jia, Yanhong; Shang, Chuang; Xu, Hongxin

2011-01-18

42

Estimation of the percolation thresholds in acyclovir hydrophilic matrix tablets.  

PubMed

The principles of percolation theory were applied to design controlled release matrix tablets containing acyclovir. This statistical theory studies disordered or chaotic systems where the components are randomly distributed in a lattice. The application of this theory to study the release and hydration rate of hydrophilic matrices allows to explain the changes in release and hydration kinetics of swellable matrix type controlled delivery systems. The objective of the present paper is to estimate the percolation threshold of HPMC K4M in matrices of acyclovir and to apply the obtained result to the design of hydrophilic matrices for the controlled delivery of this drug. Matrix tablets have been prepared using acyclovir as drug and HPMC K4M as matrix forming material, employing five different excipient/drug percentages. Dissolution studies were carried out using the paddle method. Water uptake measurements were performed using a modified Enslin apparatus. In order to estimate the percolation threshold, the behaviour of the kinetic parameters with respect to the excipient volumetric fraction at time zero plus initial porosity was studied. According to percolation theory, the critical points observed in dissolution and water uptake studies can be attributed to the excipient percolation threshold. This threshold was situated between between 20.76% and 26.41% v/v of excipient plus initial porosity. The knowledge of the percolation threshold of the components of the matrix formulations contributes to improve their design. First, reducing the time to market and second, increasing their robustness when they are prepared at Industrial scale, avoiding the formulation in the nearby of the percolation threshold. PMID:16876392

Fuertes, Inmaculada; Miranda, Antonia; Millán, Mónica; Caraballo, Isidoro

2006-11-01

43

Thermal sintering: a novel technique used in the design, optimization and biopharmaceutical evaluation of propranolol HCl gastric floating tablets.  

PubMed

The objective of the present investigation was to study the applicability of thermal sintering technique for the development of gastric floating tablets of propranolol HCl. Formulations were prepared using four independent variables, namely (i) polymer quantity, (ii) sodium bicarbonate concentration, (iii) sintering temperature and (iv) sintering time. Floating lag time and t95 were taken as dependent variables. Tablets were prepared by the direct compression method and were evaluated for physicochemical properties, in vitro buoyancy and dissolution studies. From the drug release studies, it was observed that drug retarding property mainly depends upon the sintering temperature and time of exposure. The statistically optimized formulation (PTSso) was characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry studies, and no significant chemical interaction between drug and polymer was observed. Optimized formulation was stable at accelerated conditions for a period of six months. PTSso was evaluated for in vivo buoyancy studies in humans for both fed and fasted states and found that gastric residence time of the floating tablets were enhanced by fed stage but not in fasted state. Optimized formulation PTSso and commercial formulation Ciplar LA 80 were subjected to bioavailability studies in healthy human volunteers by estimating pharmacokinetic parameters such as Cmax, Tmax, area under curve (AUC), elimination rate constant (Kel), biological half-life (t1/2) and mean residence time (MRT). There was a significant increase in the bioavailability of the propranolol HCl from PTSso formulation, which was evident from increased AUC levels and larger MRT values than Ciplar LA 80. PMID:23317339

Venkata Srikanth, Meka; Songa, Ambedkar Sunil; Nali, Sreenivasa Rao; Battu, Janaki Ram; Kolapalli, Venkata Ramana Murthy

2014-01-01

44

Thermal sintering: a novel technique in the design of gastroretentive floating tablets of propranolol HCl and its evaluation.  

PubMed

The aim of the present investigation was to formulate thermally sintered floating tablets of propranolol HCl, and to study the effect of sintering conditions on drug release, as well as their in vitro buoyancy properties. A hydrophilic polymer, polyethylene oxide, was selected as a sintered polymer to retard the drug release. The formulations were prepared by a direct compression method and were evaluated by in vitro dissolution studies. The results showed that sintering temperature and time of exposure greatly influenced the buoyancy, as well as the dissolution properties. As the sintering temperature and time of exposure increased, floating lag time was found to be decreased, total floating time was increased and drug release was retarded. An optimized sintered formulation (sintering temperature 50 degrees C and time of exposure 4 h) was selected, based on their drug retarding properties. The optimized formulation was characterized with FTIR and DSC studies and no interaction was found between the drug and the polymer used. PMID:23248967

Meka, Venkata Srikanth; Songa, Ambedkar Sunil; Nali, Sreenivasa Rao; Battu, Janaki Ram; Kukati, Latha; Kolapalli, Venkata Ramana Murthy

2012-09-01

45

Formulation and in vitro evaluation of floating tablets of hydroxypropyl methylcellulose and polyethylene oxide using ranitidine hydrochloride as a model drug.  

PubMed

The present study was carried out with an objective of preparation and in vitro evaluation of floating tablets of hydroxypropyl methyl cellulose (HPMC) and polyethylene oxide (PEO) using ranitidine hydrochloride as a model drug. The floating tablets were based on effervescent approach using sodium bicarbonate a gas generating agent. The tablets were prepared by dry granulation method. The effect of polymers concentration and viscosity grades of HPMC on drug release profile was evaluated. The effect of sodium bicarbonate and stearic acid on drug release profile and floating properties were also investigated. The result of in vitro dissolution study showed that the drug release profile could be sustained by increasing the concentration of HPMC K15MCR and Polyox WSR303. The formulation containing HPMC K15MCR and Polyox WSR303 at the concentration of 13.88% showed 91.2% drug release at the end of 24 hours. Changing the viscosity grade of HPMC from K15MCR to K100MCR had no significant effect on drug release profile. Sodium bicarbonate and stearic acid in combination showed no significant effect on drug release profile. The formulations containing sodium bicarbonate 20 mg per tablet showed desired buoyancy (floating lag time of about 2 minutes and total floating time of >24 hours). The present study shows that polymers like HPMC K15MCR and Polyox WSR303 in combination with sodium bicarbonate as a gas generating agent can be used to develop sustained release floating tablets of ranitidine hydrochloride. PMID:23493037

Gharti, Kp; Thapa, P; Budhathoki, U; Bhargava, A

2012-10-01

46

Preparation of Coated Valproic Acid and Sodium Valproate Sustained-release Matrix Tablets  

PubMed Central

The aim of this research was to investigate the technique for preparation of coated valproic acid and sodium valproate sustained-release matrix tablets. Different diluents were tested and selected as the effective absorbent for oily valproic acid. Effect of the amount of absorbent and hydroxypropylmethylcellulose on drug release from valproic acid-sodium valproate matrix tablets prepared with wet granulation technique was evaluated in pH change system. Colloidal silicon dioxide effectively adsorbed liquid valproic acid during wet granulation and granule preparation. The amounts of colloidal silicon dioxide and hydroxypropylmethylcellulose employed in tablet formulations affected drug release from the tablets. The drug release was prominently sustained for over 12 h using hydroxypropylmethylcellulose-based hydrophilic matrix system. The mechanism of drug release through the matrix polymer was a diffusion control. The drug release profile of the developed matrix tablet was similar to Depakine Chrono®, providing the values of similarity factor (f2) and difference factor (f1) of 85.56 and 2.37, respectively. Eudragit® L 30 D-55 was used as effective subcoating material for core matrix tablets before over coating with hydroxypropylmethylcellulose film with organic base solvent. Drug release profile of coated matrix tablet was almost similar to that of Depakine Chrono®.

Phaechamud, T.; Mueannoom, W.; Tuntarawongsa, S.; Chitrattha, S.

2010-01-01

47

Use of Propranolol-Magnesium Aluminium Silicate Intercalated Complexes as Drug Reservoirs in Polymeric Matrix Tablets  

PubMed Central

The objective of the present study was to investigate the use of propranolol–magnesium aluminium silicate intercalated complexes as drug reservoirs in hydroxypropylmethylcellulose tablets. The matrix tablets containing the complexes were prepared and characterised with respect to propranolol release and were subsequently compared with those loading propranolol or a propranolol–magnesium aluminium silicate physical mixture. Additionally, the effects of varying viscosity grades of hydroxypropyl methylcellulose, compression pressures and calcium acetate incorporation on the drug release characteristics of the complex-loaded tablets were also examined. The results showed that the complex-loaded tablets have higher tablet hardness than those containing propranolol or a physical mixture. The drug release from the complex-loaded tablets followed a zero-order release kinetic, whereas an anomalous transport was found in the propranolol or physical mixture tablets. The drug release rate of the complex tablet significantly decreased with increasing hydroxypropylmethylcellulose viscosity grade. Increase in the compression pressure caused a decrease in the drug release rate of the tablets. Furthermore, the incorporation of calcium ions could accelerate propranolol release, particularly in acidic medium, because calcium ions could be exchanged with propranolol molecules intercalated in the silicate layers of magnesium aluminium silicate. These findings suggest that propranolol-magnesium aluminium silicate intercalated complexes show strong potential for use as drug reservoirs in matrix tablets intended for modifying drug release.

Pongjanyakul, T.; Rojtanatanya, S.

2012-01-01

48

Investigation of critical polymer properties for polymer release and swelling of HPMC matrix tablets  

Microsoft Academic Search

Four different HPMC batches were characterized to investigate properties related to critical functionality for their use in hydrophilic matrix tablets. In this study, the HPMC batches were chemically characterized and correlated to the behaviour of pure HPMC tablets. Parameters such as the molecular weight, viscosity, intrinsic viscosity and radius of gyration were kept in a rather limited range, which resulted

Anna Viridén; Bengt Wittgren; Anette Larsson

2009-01-01

49

Preparation of highly porous gastroretentive metformin tablets using a sublimation method.  

PubMed

The present investigation is aimed to formulate floating gastroretentive tablets containing metformin using a sublimation material. In this study, the release of the drug from a matrix tablet was highly dependent on the polymer concentrations. In all formulations, initial rapid drug release was observed, possibly due to the properties of the drug and polymer. The effect of the amount of PEO on swelling and eroding of the tablets was determined. The water-uptake and erosion behavior of the gastroretentive (GR) tablets were highly dependent on the amount of PEO. The water-uptake increased with increasing PEO concentration in the tablet matrix. The weight loss from tablets decreased with increasing amounts of PEO. Camphor was used as the sublimation material to prepare GR tablets that are low-density and easily floatable. Camphor was changed to pores in the tablet during the sublimation process. SEM revealed that the GR tablets have a highly porous morphology. Floating properties of tablets and tablet density were affected by the sublimation of camphor. Prepared floating gastroretentive tablets floated for over 24 h and had no floating lag time. However, as the amount of camphor in the tablet matrix increased, the crushing strength of the tablet decreased after sublimation. Release profiles of the drug from the GR tablets were not affected by tablet density or porosity. In pharmacokinetic studies, the mean plasma concentration of the GR tablets after oral administration was greater than the concentration of glucophase XR. Also, the mean AUC(0-?) values for the GR tablets were significantly greater than the plasma concentrations of glucophase XR. PMID:23246798

Oh, Tack-Oon; Kim, Ju-Young; Ha, Jung-Myung; Chi, Sang-Cheol; Rhee, Yun-Seok; Park, Chun-Woong; Park, Eun-Seok

2013-04-01

50

Evaluation of matrix type mucoadhesive tablets containing indomethacin for buccal application.  

PubMed

Nonsteroidal anti-inflammatory drugs (NSAIDs) are administered for pain relief from oral mucositis. However, the systemic administration of NSAIDs is limited due to systemic side effects. To avoid these side effects and treat local lesions effectively, a matrix type mucoadhesive tablet was developed. A mixture of hard fat, ethylcellulose (EC) and polyethylene glycol (PEG) was used as a matrix base, and indomethacin (IMC) was used as the principal agent. In tablets consisting of hard fat, EC and IMC, the drug release was sustained. In tablets consisting of hard fat, EC, considerable amounts of PEG and IMC, the drug release was relatively increased and IMC existed as the molecular phase or in an amorphous state. The in vitro adhesive force of the tablets consisting of hard fat, EC, considerable amounts of PEG and IMC was significantly increased as compared with the tablets consisting of hard fat and IMC. A significantly high tissue concentration and significantly low plasma concentration were observed after buccal administration of this matrix type mucoadhesive tablet as compared with that after oral administration of IMC. Thus, the matrix type mucoadhesive tablet has good potential as a preparation for the treatment of pain due to oral aphtha. PMID:23791737

Ikeuchi-Takahashi, Yuri; Sasatsu, Masanaho; Onishi, Hiraku

2013-09-10

51

Immunolocalization of matrix proteins in nacre lamellae and their in vivo effects on aragonitic tablet growth.  

PubMed

How matrix proteins precisely control the growth of nacre lamellae is an open question in biomineralization research. Using the antibodies against matrix proteins for immunolabeling and in vivo experiments, we investigate the structural and functional roles of EDTA-soluble matrix (SM) and EDTA-insoluble matrix (ISM) proteins in nacre biomineralization of the pearl oyster Pinctada fucata. Immunolabeling reveals that a SM protein, nacrein, distributes within aragonitic tablets and intertabular matrix. An ISM protein, which we named P43, has been specifically recognized by polyclonal antibodies raised against the recombinant protein of P. fucata bone morphogenetic protein 2 in immunoblot analysis. Immunolabeling indicates that P43 is localized to interlamellar sheet, and also embedded within aragonitic tablets. Although nacrein and P43 both distribute within aragonitic tablets, they function differently in aragonitic tablet growth. When nacrein is suppressed by the antibodies against it in vivo, crystal overgrowth occurs, indicating that this SM protein is a negative regulator in aragonitic tablet growth. When P43 is suppressed in vivo, the organo-mineral assemblage is disrupted, suggesting that P43 is a framework matrix. Taken together, SM and ISM proteins are indispensable factors for the growth of nacre lamellae, controlling crystal growth and constructing the framework of aragonitic tablets. PMID:18620869

Gong, Ningping; Shangguan, Junlong; Liu, Xiaojun; Yan, Zhenguang; Ma, Zhuojun; Xie, Liping; Zhang, Rongqing

2008-10-01

52

Formulation, evaluation and optimization of sustained release matrix tablets of captopril  

PubMed Central

Sustained release matrix tablet is a delivery system by which the drug can be delivered at a controlled rate for long period of time. The present study aims at formulation, evaluation and optimization of captopril matrix tablets. A 32 full factorial design was adopted and all 9 batches were prepared by wet granulation method. Prepared granules and tablets were evaluated for precompression and postcompression characteristics respectively. Check point analysis was applied to the observations and the formula of the tablet was optimized. Optimized formula, F6 showed zero order drug release kinetics for the time period of 24 hours i.e. 17.55% release at the end of 2 hours, 53.4% release at the end of 12 hours and 100.24% release at the end of 24 hours. The results revealed that concentration of matrix forming agent and solution of granulating agent significantly affected in vitro drug release profile.

Pandya, V. Pandya; Patel, Vandana B.; Patel, Prajesh

2012-01-01

53

Solid Dispersion Matrix Tablet Comprising Indomethacin-PEG-HPMC Fabricated with Fusion and Mold Technique  

PubMed Central

The purpose of this study is to fabricate the polyethylene glycol matrix tablet by mold technique. Indomethacin and hydroxypropylmethylcellulose were used as model drug and polymer, respectively, in PEG matrix system. The physical and drug release characteristics of developed matrix tablet were studied. This inert carrier system comprising 7:3 polyethylene glycol 4000: polyethylene glycol 400 could effectively enhance the solubility of indomethacin and an addition of hydroxypropylmethylcellulose could sustain the drug release. Scanning electron microscope photomicrograph indicated the drug diffusion outward through the porous network of this developed matrix tablet into the dissolution fluid. Least square fitting the experimental dissolution data to the mathematical expressions (power law, first-order, Higuchi's and zero-order) indicated the drug release kinetics primarily as Fickian diffusion. Both the enhancement of drug dissolution and the prolongation of the drug release could be achieved for aqueous insoluble drug such as, indomethacin, by using polyethylene glycol-hydroxypropylmethylcellulose matrix system prepared with melting and mold technique.

Mesnukul, A.; Yodkhum, K.; Phaechamud, T.

2009-01-01

54

In vitro controlled release of sodium ferulate from Compritol 888 ATO-based matrix tablets.  

PubMed

A controlled release matrix formulation for freely water-soluble drug of sodium ferulate (SF) was designed and developed to achieve a 24h release profile. Using Compritol 888 ATO as an inert matrix-forming agent to control the release of SF, formulation granules containing the physical mixtures or solid dispersions were investigated. The matrix tablets for these formulations were prepared by direct compression and their in vitro release tests were carried out. The solid dispersion based tablets were found to be more effective than those compressed from physical mixtures in retarding the release of SF. Drug release from the matrix tablets containing physical mixtures nearly completed within 12h, while that from the solid dispersion formulations lasted for over 24h. Images of the tablet surface and cross-section were characterized by scanning electron microscopy to show the formed pores and channels in the matrices. These might provide the release pathway for the inner embedded drugs. Drug released fast from the matrix tablets with the release-enhancer of lactose. The addition of surfactants was also found to increase the release rate of SF effectively. Moreover, the co-mixing of polyethylene glycol 6000 (PEG 6000) in the waxy matrices played a meaningful role in controlling the drug release for 24h. The drug release from the novel formulation might be attributed to the diffusion-controlled mechanism. PMID:16837152

Li, Feng-Qian; Hu, Jin-Hong; Deng, Jia-Xin; Su, Hua; Xu, Shu; Liu, Ji-Yong

2006-11-01

55

Formulation and Evaluation of Once Daily Minocycline Hydrochloride Extended Release Matrix Tablets  

PubMed Central

The present study was aimed to develop once daily extended release matrix tablets of minocycline hydrochloride, using hydroxypropylmethylcellulose either alone or in combination with ethyl cellulose as the matrix material in different proportions. The formulated tablets were also compared with a marketed product. The results of the dissolution study indicate that formulations FC-IV, FC-V and FC-VI showed maximum drug release upto 24 h, whereas the marketed product was found to extend the release only up to 14 h. Incase of formulations containing combination of hydroxypropylmethylcellulose and ethyl cellulose (FC-I to FC-IX), the release of the drug was found to be dependent on the relative proportions of hydroxypropylmethylcellulose and ethyl cellulose used in the tablet matrix. Mathematical treatment of the in vitro drug release data suggests that, all the formulations best fitted into first order release kinetics. Drug release from the matrix occurred by combination of two mechanisms, diffusion of drug from tablet matrix and erosion of tablet surface, which was reflected from Higuchi's model and Erosion plot.

Keny, R. V.; Mankame, S. A.; Lourenco, C. F.

2009-01-01

56

Controlled-Release Carbamazepine Granules and Tablets Comprising Lipophilic and Hydrophilic Matrix Components  

PubMed Central

The objective of this study was to investigate the effect of lipophilic (Compritol® 888 ATO) and hydrophilic components (combination of HPMC and Avicel) on the release of carbamazepine from granules and corresponding tablet. Wet granulation followed by compression was employed for preparation of granules and tablets. The matrix swelling behavior was investigated. The dissolution profiles of each formulation were compared to those of Tegretol® CR tablets and the mean dissolution time (MDT), dissolution efficiency (DE %) and similarity factor (f2 factor) were calculated. It was found that increase in the concentration of HPMC results in reduction in the release rate from granules and achievement of zero-order is difficult from the granules. The amount of HPMC plays a dominant role for the drug release. The release mechanism of CBZ from matrix tablet formulations follows non-Fickian diffusion shifting to case II by the increase of HPMC content, indicating significant contribution of erosion. Increasing in drug loading resulted in acceleration of the drug release and in anomalous controlled-release mechanism due to delayed hydration of the tablets. These results suggest that wet granulation followed by compression could be a suitable method to formulate sustained release CBZ tablets.

Elbagory, Ibrahim M.; Almurshedi, Alanood S.

2008-01-01

57

The Role of Oral Controlled Release Matrix Tablets in Drug Delivery Systems  

PubMed Central

Formulations that are able to control the release of drug have become an integral part of the pharmaceutical industry. In particular oral drug delivery has been the focus of pharmaceutical research for many years. This type of drug delivery has been at the centre of research due to its many benefits over conventional dosage. The focus of this review is on matrix tablets due to their widely use and simplicity of the formulation. This includes the discussion of various types of matrix tablets and factors affecting the drug release from these formulations. The mechanism of drug release from HPMC matrices is also discussed.

Nokhodchi, Ali; Raja, Shaista; Patel, Pryia; Asare-Addo, Kofi

2012-01-01

58

Floating Matrix Dosage Form for Propranolol Hydrochloride Based on Gas Formation Technique: Development and In Vitro Evaluation  

PubMed Central

Gastroretentive tablets of propranolol hydrochloride were developed by direct compression method using citric acid and sodium bicarbonate as the effervescent base. Hydroxypropyl methylcellulose; HPMC K15M was used to prepare the floating tablets to retard the drug release for 12h in stomach. Na-carboxymethyl cellulose (NaCMC) or carbopol 934P was added to alter the drug release profile or the dimensional stability of the formulation. Dicalcium phosphate (DCP) was used as filler. Formulations were evaluated for floating lag time, duration of floating, dimensional stability, drug content and in vitro drug release profile. The formulations were found to have floating lag time less than 1min. It was found that the dimensional stability of the formulations increase with increasing concentration of the swelling agent. The release mechanism of propranolol hydrochloride from floating tablets was evaluated on the basis of Peppas and Higuchi model. The ‘n’ value of the formulations ranged from 0.5201 to 0.7367 (0.5

Chaturvedi, Kiran; Umadevi, S.; Vaghani, Subhash

2010-01-01

59

Scalable and Modular Algorithms for Floating-Point Matrix Multiplication on Reconfigurable Computing Systems  

Microsoft Academic Search

The abundant hardware resources on current reconfigurable computing systems provide new opportunities for high-performance parallel implementations of scientific computations. In this paper, we study designs for floating-point matrix multiplication, a fundamental kernel in a number of scientific applications, on recon- figurable computing systems. We first analyze design tradeoffs in implementing this kernel. These tradeoffs are caused by the inherent parallelism

Ling Zhuo; Viktor K. Prasanna

2007-01-01

60

Scalable and Modular Algorithms for Floating-Point Matrix Multiplication on FPGAs  

Microsoft Academic Search

The abundant hardware resources on current FPGAs provide new opportunities to improve the performance of hardware implementations of scientific computations. In this paper, we propose two FPGA-based algorithms for floating-point matrix multiplication, a fundamental kernel in a number of scientific applications. We analyze the de- sign tradeoffs in implementing this kernel on FPGAs. Our algorithms employ a linear array architecture

Ling Zhuo; Viktor K. Prasanna

2004-01-01

61

Optimization of bilayer floating tablet containing metoprolol tartrate as a model drug for gastric retention  

Microsoft Academic Search

The purpose of the present study was to develop an optimized gastric floating drug delivery system (GFDDS) containing metoprolol\\u000a tartrate (MT) as a model drug by the optimization technique. A 23 factorial design was employed in formulating the GFDDS with total polymer content-to-drug ratio (X1), polymer-to-polymer ratio (X2), and different viscosity grades of hydroxypropyl methyl cellulose (HPMC) (X3) as independent

C. Narendra; M. S. Srinath; Ganesh Babu

2006-01-01

62

Effect of Kollidon® SR on the release of Albuterol Sulphate from matrix tablets.  

PubMed

The objective of this study was to evaluate Kollidon SR for the development of extended release Albuterol Sulphate matrix tablets in comparison with other polymers as Hydroxypropylmethylcellulose K15M, Carbopol 71G NF, and Eudragit L100-55. The mechanical properties of the tablets were improved as concentration of Kollidon SR or other polymers increased. It was found that Kollidon SR 30% (w/w) and HPMC 30% (w/w) tablets have f 2 similarity factor of 83.5 in their Albuterol Sulphate dissolution profile. The marketed product was found to release 99.7% of drug content within 8 h, while Kollidon SR and HPMC tablets with 30% (w/w) polymer concentration level released 92.7% and 92.9% respectively of drug content within 8 h. Kollidon SR has a unique character of maintaining tablets geometric shape until the end of dissolution test, this is mainly due to the water insoluble content, polyvinyl acetate, forming 80% (w/w) of Kollidon SR, while the remaining content 20% (w/w) is the water soluble, polyvinylpyrrolidone, responsible for pore formation causing a diffusion controlled release. Drug release from all previous formulations is best described to be controlled by more than one kinetic mechanism of release. In conclusion, Kollidon SR and HPMC and Carbopol were found to be potential candidates for the development of extended release of Albuterol Sulphate tablets. PMID:24115901

Sakr, Walid; Alanazi, Fars; Sakr, Adel

2011-01-01

63

Colonic luminal surface retention of meloxicam microsponges delivered by erosion based colon-targeted matrix tablet.  

PubMed

The work was aimed at developing calcium-pectinate matrix tablet for colon-targeted delivery of meloxicam (MLX) microsponges. Modified quassi-emulsion solvent diffusion method was used to formulate microsponges (MS), based on 3(2) full factorial design. The effects of volume of dichloromethane and EudragitRS100 content (independent variables) were determined on the particle size, entrapment efficiency and %cumulative drug release of MS1-MS9. The optimized formulation, MS5 (d(mean)=44.47 ?m, %EE=98.73, %CDR=97.32 and followed zero order release) was developed into colon-targeted matrix tablet using calcium pectinate as the matrix. The optimized colon-targeted tablet (MS5T2) shielded MLX loaded microsponges in gastrointestinal region and selectively delivered them to colon, as vizualized by vivo fluoroscopy in rabbits. The pharmacokinetic evaluation of MS5T2 in rabbits, revealed appearance of drug appeared in plasma after a lag time of 7h; a t(max) of 30 h with Fr=61.047%, thus presenting a formulation suitable for targeted colonic delivery. CLSM studies provided an evidence for colonic luminal retentive ability of microsponges at the end of 8h upon oral administration of MS5T2. Thus calcium pectinate matrix tablet loaded with MLX microsponges was developed as a promising system for the colon-specific delivery that has potential for use as an adjuvant therapy for colorectal cancer. PMID:22306039

Srivastava, Rishabh; Kumar, Deepesh; Pathak, Kamla

2012-05-10

64

Effect of the drug-matrix on the stability of enalapril maleate in tablet formulations  

Microsoft Academic Search

The chemical stability of enalapril maleate in tablet dosage forms consisting of different formulation excipients has been studied in this work. The influence of various parameters such as heat, moisture, light and the drug-matrix was investigated. The degradation of enalapril maleate has been followed by using an HPLC method, which was demonstrated to be specific, stability indicating, accurate and precise.

M. M Al-Omari; M. K Abdelah; A. A Badwan; A. M. Y Jaber

2001-01-01

65

In vitro characterization and release study of Ambroxol hydrochloride matrix tablets prepared by direct compression.  

PubMed

A series of either hydrophilic or hydrophobic polymers were used to prepare controlled release Ambroxol hydrochloride (AMX) matrix tablets by direct compression. Both the compatibility and flow properties of AMX/polymer mixtures were investigated. The effect of the amount and type of polymer on the physical properties and in vitro drug release was studied and compared to commercially available Ambroxol(®) SR capsules. A kinetic study of the release profile of AMX from the prepared matrix tablets was performed. All excipients used in the study were compatible with the model drug. AMX/drug mixtures containing sodium alginate (NA) and hydroxypropylmethyl cellulose (HPMC) showed better flow properties than other polymers used in the study. The in vitro drug release studies showed that matrix tablets formulae containing 10% HPMC (S7) or a combination of 30% NA and 5% HPMC (Ah) exhibited a higher ability to control the release of AMX. The kinetic study revealed that a diffusion controlled mechanism prevailed except when carbopol was used. Formula Ah followed a non-fickian diffusion mechanism similar to Ambroxol(®) SR capsules. Both formulae S7 and Ah could be considered as potential candidates for formulation of AMX controlled release matrix tablets. PMID:21428699

Abd-Elbary, A; Haider, M; Sayed, S

2012-01-01

66

Formulation and evaluation of sustained release matrix tablet of rabeprazole using wet granulation technique  

PubMed Central

Introduction: Rabeprazole, a member of substituted benzimidazoles, inhibits the final step in gastric acid secretions. This drug claims to cause fastest acid separation (due to higher pKa), and more rapidly converts to the active species to aid gastric mucin synthesis. The most significant pharmacological action of Rabeprazole is dose dependent suppression of gastric acid secretion; without anticholinergic or H2-blocking action. It completely abolishes the hydrochloric acid secretion as it is powerful inhibitor of gastric acid. Rabeprazole is acid labile and hence commonly formulated as an enteric coated tablet. The absorption of rabeprazole occurs rapidly as soon as tablet leaves the stomach. Aim: In the present study an attempt was made to formulate and evaluate Rabeprazole sustained release matrix tablet using wet granulation technique incorporating various polymers like HPMC-E15, Carbopol934, and sodium carboxymethyl cellulose (CMC). Materials and Methods: The Formulated tablets were evaluated for different physicochemical properties like rheological properties, weight variation, thickness, hardness, % friability, in vitro release studies and drug content. Results: Studies revealed that all the physicochemical parameters comply with the official standards. The in vitro release studies exhibits the release up to 90%, over a prolonged period of time which confirms the extended release profile of formulation, having better bioavailability as well as decreased dosing frequency with reduced doses. Conclusion: The sustained release matrix tablets of rabiprazole shown better bioavailability, efficacy and potency, when compared with official standards.

Khan, Ruqaiyah; Ashraf, Md Shamim; Afzal, Muhammad; Kazmi, Imran; Jahangir, Mohammed Asadullah; Singh, Rajbala; Chandra, Ramesh; Anwar, Firoz

2014-01-01

67

Matrix-mini-tablets of lornoxicam for targeting early morning peak symptoms of rheumatoid arthritis  

PubMed Central

Objective(s): The aim of present research was to develop matrix-mini-tablets of lornoxicam filled in capsule for targeting early morning peak symptoms of rheumatoid arthritis. Materials and Methods: Matrix-mini-tablets of lornoxicam were prepared by direct compression method using microsomal enzyme dependent and pH-sensitive polymers which were further filled into an empty HPMC capsule. To assess the compatibility, FT-IR and DSC studies for pure drug, polymers and their physical mixture were performed. The formulated batches were subjected to physicochemical studies, estimation of drug content, in vitro drug release, drug release kinetics, and stability studies. Results: When FTIR and DSC studies were performed it was found that there was no interaction between lornoxicam and polymers which used. All the physicochemical properties of prepared matrix-mini-tablets were found to be in normal limits. The percentage of drug content was found to be 99.60±0.07%. Our optimized matrix mini-tablets-filled-capsule formulation F30 released lornoxicam after a lag time of 5.02±0.92 hr, 95.48±0.65 % at the end of 8 hr and 99.90±0.83 % at the end of 12 hr. Stability was also found for this formulation as per the guidelines of International Conference on Harmonisation of Technical Requirements of Pharmaceuticals for Human Use. Conclusion: A novel colon targeted delivery system of lornoxicam was successfully developed by filling matrix-mini-tablets into an empty HPMC capsule shell for targeting early morning peak symptoms of rheumatoid arthritis.

Mohd, Abdul Hadi; Raghavendra Rao, Nidagurthi Guggilla; Avanapu, Srinivasa Rao

2014-01-01

68

Use of hydrophilic natural gums in formulation of sustained-release matrix tablets of tramadol hydrochloride.  

PubMed

The objective of this work was to develop matrix sustained-release tablets of highly water-soluble tramadol HCl using natural gums (xanthan [X gum] and guar [G gum]) as cost-effective, nontoxic, easily available, and suitable hydrophilic matrix systems compared with the extensively investigated hydrophilic matrices (ie, hydroxypropyl methylcellulose [HPMC]/carboxymethyl cellulose [CMC] with respect to in vitro drug release rate) and hydration rate of the polymers. Matrix tablets of tramadol (dose 100 mg) were produced by direct compression method. Different ratios of 100:0, 80:20, 60:40, 20:80, 0:100 of G gum (or X):HPMC, X gum:G gum, and triple mixture of these polymers (G gum, X gum, HPMC) were applied. After evaluation of physical characteristics of tablets, the dissolution test was performed in the phosphate buffer media (pH 7.4) up to 8 hours. Tablets with only X had the highest mean dissolution time (MDT), the least dissolution efficiency (DE(8)%), and released the drug following a zero-order model via swelling, diffusion, and erosion mechanisms. Guar gum alone could not efficiently control the drug release, while X and all combinations of natural gums with HPMC could retard tramadol HCl release. However, according to the similarity factor (f(2) ), pure HPMC and H(8)G(2) were the most similar formulations to Topalgic-LP as the reference standard. PMID:16584155

Varshosaz, Jaleh; Tavakoli, Naser; Kheirolahi, Fatemeh

2006-01-01

69

Effect of the drug-matrix on the stability of enalapril maleate in tablet formulations.  

PubMed

The chemical stability of enalapril maleate in tablet dosage forms consisting of different formulation excipients has been studied in this work. The influence of various parameters such as heat, moisture, light and the drug-matrix was investigated. The degradation of enalapril maleate has been followed by using an HPLC method, which was demonstrated to be specific, stability indicating, accurate and precise. The degradation kinetics of enalalpril maleate in phosphate buffer solutions of pH values in the range of 2.2-10.5 were observed to be psuedo first order throughout the whole pH range studied. Enalapril maleate alone showed high stability for temperature under dry and humid conditions, however it became unstable when mixed with the drug-matrix in its tablet formulations and exposed to the same conditions. The pathway of degradation of enalapril maleate was found to be pH dependent. The extent of degradation of two different enalapril maleate tablet formulations (product A of a basic drug-matrix and product B of an acidic drug-matrix) has been investigated. The degree of degradation of the product with acidic matrix was significantly less than that of the basic matrix under same temperature and humidity conditions. In fact, diketopiperazine and enalaprilat degradants were mainly associated with the degradation of the product with the acidic matrix and that with the basic matrix, respectively. Dry enalapril maleate powder showed some photolysis, which was more significant with daylight (3.3%) compared with that under UV light (0.2%). Although the product with the acidic matrix showed some photolysis but the effect was not pronounced and the % recovery of enalapril was almost complete and within the acceptable experimental errors. However, the product with the basic matrix showed almost no response for photolysis. PMID:11377072

Al-Omari, M M; Abdelah, M K; Badwan, A A; Jaber, A M

2001-07-01

70

Simultaneous probing of swelling, erosion and dissolution by NMR-microimaging—Effect of solubility of additives on HPMC matrix tablets  

Microsoft Academic Search

Extensive studies of extended release tablets based on hydrophilic polymers have illuminated several aspects linked to their functionality. However, in some respects key factors affecting the mechanisms of release are yet unexplored. In the present study, a novel NMR-microimaging method has been used to study the influence of the solubility of additives in extended release hydroxypropyl methylcellulose (HPMC) matrix tablets.

Farhad Tajarobi; Susanna Abrahmsén-Alami; Anders S. Carlsson; Anette Larsson

2009-01-01

71

Influence of the viscosity grade and the particle size of HPMC on metronidazole release from matrix tablets  

Microsoft Academic Search

Matrix tablets of metronidazole with hydroxypropyl methylcellulose (HPMC) were prepared by granulation with water and compaction at 127 MPa in a hydraulic press. The release profile of the obtained tablets was evaluated with the USP 23 apparatus 2 (paddle) at 100 rpm and using 0.1 N HCl as the medium. The influence of the HPMC viscosity grade and particle size

María Elena Campos-Aldrete; Leopoldo Villafuerte-Robles

1997-01-01

72

FABRICATION AND IN VITRO EVALUATION OF CHITOSAN MATRIX TABLETS OF DICLOFENAC ON COLON DRUG DELIVERY SYSTEM (CODES)  

Microsoft Academic Search

The objective of this study is to fabricate and Evaluate Chitosan Matrix tablets of Diclofenac.The effect of various polymers like ethyl cellulose, cellulose acetate phthalate on the release of Diclofenac have been evaluated. Tablets were evaluated for physical and chemical parameters such as Hardness, Friability, Thickness, Weight variation, Drug Content uniformity and invitro release. All batches are complied physical and

A. ABIRAMI; S. MOHAMED HALITH; S. JAYAPRAKASH; R. SENTHIL PRABHU; K. KULATHURAN PILLAI

73

Biphasic release of indomethacin from HPMC/pectin/calcium matrix tablet: I. Characterization and mechanistic study.  

PubMed

Calcium-induced crosslinking of pectin acts as the dominating factor controlling drug release from pectin-based matrices. The same interaction was employed to modify indomethacin release from HPMC/pectin/calcium matrix in this study. The aim was to characterize the release profiles, and to study the formulation variables and the underlying mechanisms. The matrix tablet was made up of pectin HM 70, calcium chloride and HPMC K4M, and prepared by the wet granulation method. In vitro release was performed in water and characterized by the power law. Matrix erosion was evaluated by studying the weight loss and pectin release. Biphasic release of indomethacin from the HPMC/pectin/calcium matrix tablet was observed, and extraordinary power law exponent n values of over 1.0 were observed. Increase in calcium amount led to more significant retardation on drug release. The two power law parameters, n and K, correlated to the amount of calcium in the matrix. A lag time of over 4 h can be achieved at HPMC/pectin/calcium chloride amount of 100 mg/100 mg/100 mg. Both matrix weight loss and pectin release were linearly correlated to indomethacin release, indicating erosion-controlled drug release mechanisms. The hybrid matrix showed retarded erosion and hydration rate, which served as the basis for retarded indomethacin release. It is concluded that the pectin/calcium interaction can be employed to modify drug release from HPMC/pectin/calcium matrix tablet with biphasic release patterns for potential timed or site-specific drug delivery. PMID:17540549

Wu, Baojian; Chen, Zhukang; Wei, Xiuli; Sun, Ningyun; Lu, Yi; Wu, Wei

2007-11-01

74

Hydration, erosion, and release behavior of guar-based hydrophilic matrix tablets containing total alkaloids of Sophora alopecuroides.  

PubMed

It is a challenge to deliver water-soluble drug based on hydrophilic matrix to colon because of swelling and erosion of polysaccharides in contact with media. In our study, guar-based hydrophilic matrix tablets containing water-soluble total alkaloids of Sophora alopecuroides prepared by wet granulation technique were evaluated. A novel method was established to investigate the changes of swelling and volume for guar-based tablets in undynamic state, which generally showed a rapid swelling and volume change in the first 9 h, then the hydrated speed slowed down. On the other hand, the influence of different pH of the media on water uptake and erosion of various guar-based formulations in dynamic state indicated that the hydrated constants in simulated gastric fluid (SGF) was higher than that in SIF, which followed varied mechanism of water penetration by fitting Davidson and Peppas model. The extent of erosion was between 22.4 and 32.6% in SIF within 360 min. In vitro sophoridine release studies in successive different mimicking media showed that the guar matrix tablets released 13.5-25.6% of sophoridine in the first 6 h; therefore it was necessary to develop the bilayer matrix tablet by direct-compressing coating 100 mg guar granula on core tablet. The initial release of coated tablet was retarded and the bilayer matrix tablet was suitable for colon target. PMID:19040179

Zhao, Wenchang; Song, Lijun; Deng, Hongzhu; Yao, Hui

2009-05-01

75

Three-layer guar gum matrix tablet formulations for oral controlled delivery of highly soluble trimetazidine dihydrochloride  

Microsoft Academic Search

The present study is carried out to design oral controlled drug delivery systems for highly water-soluble drugs using guar gum as a carrier in the form of three-layer matrix tablets. Trimetazidine dihydrochloride was chosen as a model drug because of its high water solubility. Matrix tablet granules containing 30% (M1), 40% (M2) or 50% (M3) of guar gum were prepared

Y. S. R. Krishnaiah; R. S. Karthikeyan; V. Gouri Sankar; V. Satyanarayana

2002-01-01

76

[Determination of diclofenac sodium and codeine phosphate in shuerfen tablets by CPA-matrix method].  

PubMed

The contents of diclofenac sodium and codeine phosphate in shuerfen tablets may be determined simultaneously by CPA-matrix method without separation of its components. The program was edited by BASIC. The average recoveries and RSD were 99.85%, 0.46% for diclofenac sodium and 99.80%, 0.50% codeine phosphate, respectively. This method is simple and rapid, and the result is accurate. PMID:15819020

Yang, C; Ding, L; Liu, W; Zhang, Z

1999-04-01

77

Development of metoprolol tartrate extended-release matrix tablet formulations for regulatory policy consideration  

Microsoft Academic Search

This research study was designed to develop model extended-release (ER) matrix tablet formulations for metoprolol tartrate (100 mg) sufficiently sensitive to manufacturing variables and to serve as the scientific basis for regulatory policy development on scale-up and post approval changes for modified-release dosage forms (SUPAC-MR). Several grades and levels of hydroxypropyl methylcellulose (Methocel K4M, K15M, K100M and K100LV), fillers and

Ranjani V Nellore; Gurvinder Singh Rekhi; Ajaz S Hussain; Lloyd G Tillman; Larry L Augsburger

1998-01-01

78

Effect of solvents on physical properties and release characteristics of monolithic hydroxypropylmethylcellulose matrix granules and tablets  

Microsoft Academic Search

Effect of solvents on physical characteristics and release characteristics of monolithic acetaminophen (APAP) hydroxypropylmethylcellulose\\u000a (HPMC) matrix granules and tablets were examined. Various types and amounts of solvents were employed for granulation and\\u000a coating. APAP and other excipients were mixed and were then wet-granulated in a high-speed mixer. The dried granules were\\u000a then directly compressed and film-coated with low viscosity grade

Qing-Ri Cao; Yun-Woong Choi; Jing-Hao Cui; Beom-Jin Lee

2005-01-01

79

Designing an extended release waxy matrix tablet containing nicardipine-hydroxy propyl ? cyclodextrin complex  

PubMed Central

Aim The current study aimed to prepare a sustained release tablet for a drug which has poor solubility in alkaline medium using complexation with cyclodextrin. Nicardipine hydrochloride (NC) a weak basic drug was chosen as a model drug for this study. Method Firstly the most suitable binary system NC-HP?CD was selected in order to improve drug solubility in the intestinal media and then embedding the complexed drug into a plastic matrix, by fusion method, consists of glycerol monostearate (GMS) as an inert waxy substance and polyethylene glycol 4000 (PEG4000) as a channeling agent, after that the final solid dispersion [(NC:HP?CD):GMS:PEG4000] which was prepared at different ratios was mixed with other excipients, avicel PH101, lactose, and talc, to get a tablet owning dissolution profile complying with the FDA and USP requirements for the extended release solid dosage forms. Results Infrared spectroscopy (IR), differential scanning colorimetry (DSC), polarized microscopy and X-ray diffractometry proved that the coevaporation technique was effective in preparing amorphous cyclodextrin complexes with NC and trapping of NC within the HP?CD cavity by dissolving both in ethanol and evaporate the solvent using a rotavapor at 65 °C. Dissolution profile of NC enhanced significantly in pH 6.8 from NC:HP?CD inclusion complex prepared by the rotavapor (t-test Student p < 0.05). The release of NC from tablet containing [(NC:HP?CD):GMS:PEG4000] [(1):0.75:0.5] (w/w/w) solid dispersion (F8) was complying with the FDA dissolution requirements for extended release dosage forms, and studying the kinetics of the release showed that the diffusional contribution is the major factor controlling the drug release from that formula. Conclusion The prepared waxy matrix tablet containing NC complexes with CD shows promising results as extended release tablets.

Al-Zein, Hind; Sakeer, Khalil; Alanazi, Fars K.

2011-01-01

80

Formulation and evaluation of polyelectrolyte complex-based matrix tablet of Isosorbide Mononitrate  

PubMed Central

Introduction: The polyelectrolyte Complexes (PECs) are based on ionic cross-linking. They have been employed to prepare a sustained release matrix tablets. These systems are based upon the fact that their structure can entrap the drug within them. Isosorbide Mononitrate (ISMN) is an anti-anginal organic nitrate vasodilator used in the treatment of various cardiovascular disorders and prophylaxis of angina Pectoris, which is poorly absorbed from the upper GIT, hence CR formulation is desirable. Materials and Methods: Chitosan (CH)/Sodium alginate (SA), Guar gum (GG), and Xanthan gum (XG) were used as PECs, and were prepared using different proportions i.e., in 1:1 and 1:2 ratio. The optimum ratio of CH: SA, CH: GG and CH: XG was in the ratio was 1:2; these are formed due to electrostatic interaction between oppositely charged poly ions. These normally employ a hydrophilic matrix system. Matrix tablet of ISMN was formulated by using PECs as matrix forming agent by wet granulation technique. Results: The tablets were evaluated for hardness, wt variation, drug content, and in-vitro dissolution studies and found to be within limits. Release kinetics data indicated that ISMN released from the PECs-based matrix tablets of CH-SA, CH-GG and CH-XG CP in 1:1 and 1:2 ratio, followed Fickian and non-Fickian diffusion mechanism respectively. Thus, the drug release rate was extended for over a period of more than 12 h stability studies. There is no significant difference in the mean % drug released from formulation CH-X2 after storing for 3 months at 40°C/75% RH. The FT-IR spectra revealed that there was no interaction between polymers and drug, Statistical analysis showed a significant differences (P < 0.05) for the amount of ISMN released from the formulations (MXG) and formulations (CH-X2). Conclusion: Formulation CH-XG2 (1:2) showed better sustained release of highly water-soluble ISMN with the desired release rate. Thus, the formulated PECs-based matrix tablets seems to be a potential candidate for sustained drug delivery of highly soluble drug ISMN in the symptomatic therapy of angina pectoris.

Syed, Iizhar Ahmed; Niveditha, P.; Ahmad, Ismail

2014-01-01

81

Formulation and Evaluation of Hydroxypropyl Methylcellulose-based Controlled Release Matrix Tablets for Theophylline  

PubMed Central

The objectives of the study were to formulate hydroxypropyl methyl cellulose-based controlled release matrix tablets for theophylline with varying drug:polymer ratios (1:1 and 1:2) and differing tablet hardness (5, 6 and 7 kg/cm2), and to evaluate the tablet's physico-chemical properties such as hardness, uniformity of weight, friability, drug content and in vitro drug release. Initially, granules were made by wet granulation technique and evaluated for angle of repose, bulk density, tapped density, bulkiness, compressibility index and hausner ratio. The results indicate good flow property of the granules and thus, the evaluated tablet physical properties were within the acceptable limits. The FT-IR study for the F-6 formulation showed that there was no interaction between the drug and the polymer. In vitro release studies were performed using Disso-2000 (paddle method) in 900 ml of pH 7.4 at 50 rpm. The result indicated that at high drug:polymer ratio (1:2) and hardness value 7 kg/cm2, prolonged drug release was observed than the low drug: polymer ratio (1:1) and hardness values (5 and 6 kg/cm2). The release kinetics was found to follow korsmeyers-peppas model and the mechanism of drug release was by non-fickian or anomalous diffusion. The F-6 formulation was chosen for stability studies. F-6 formulation was stable when it was kept at different temperatures for a period of 6 months.

Sekharan, T. Raja; Palanichamy, S.; Tamilvanan, S.; Shanmuganathan, S.; Thirupathi, A. Thanga

2011-01-01

82

Drug release characteristics from chitosan-alginate matrix tablets based on the theory of self-assembled film.  

PubMed

The aim of this study was to better understand the underlying drug release characteristics from chitosan-alginate matrix tablets containing different types of drugs. Theophylline, paracetamol, metformin hydrochloride and trimetazidine hydrochloride were used as model drugs exhibiting significantly different solubilities (12, 16, 346 and >1000 mg/ml at 37 °C in water). A novel concept raised was that drugs were released from chitosan-alginate matrix tablets based on the theory of a self-assembled film-controlled release system. The film was only formed on the surface of tablets in gastrointestinal environment and originated from chitosan-alginate polyelectrolyte complex, confirmed by differential scanning calorimetry characterization. The formed film could decrease the rate of polymer swelling to a degree, also greatly limit the erosion of tablets. Drugs were all released through diffusion in the hydrated matrix and polymer relaxation, irrespective of the drug solubility. The effects of polymer level and initial drug loading on release depended on drug properties. Drug release was influenced by the change of pH. In contrast, the impact of ionic strength of the release medium within the physiological range was negligible. Importantly, hydrodynamic conditions showed a key factor determining the superiority of the self-assembled film in controlling drug release compared with conventional matrix tablets. The new insight into chitosan-alginate matrix tablets can help to broaden the application of this type of dosage forms. PMID:23624081

Li, Liang; Wang, Linlin; Shao, Yang; Ni, Rui; Zhang, Tingting; Mao, Shirui

2013-06-25

83

Development of polysaccharide based colon targeted drug delivery system: design and evaluation of Assam Bora rice starch based matrix tablet.  

PubMed

The aim of this study was to develop a novel colon targeted matrix tablet containing Metronidazole (MTZ) as model drug. Matrix tablets were prepared using Assam Bora rice starch, which is essentially a natural polymer, by wet granulation technique. The granules prepared were subjected to evaluation for angle of repose, bulk density, compressibility index, Hausner's ratio, total porosity, and drug content. The developed tablets were also analysed for thickness, diameter, weight variation tests, tablet crushing strength, friability, and in vitro release studies. The granules displayed satisfactory flow properties, compressibility, Hausner's ratio and drug content. Almost all the tablet formulations showed acceptable pharmacotechnical properties and complied with the in-house developed specifications for the tested parameters. Drug release study confirmed to the initial fast release in the acidic environment of surface adhered drug followed by slow release in alkaline media subsequently leading to fast and major drug release in the caecal content. Furthermore, the release of drug was unaffected by the hostile environment of GIT which can be ascribed to microbial degradation, promptly followed by enzymatic degradation. Curve fitting proved that the drug release from the tablets followed the Higuchi model. In vitro bacterial inhibition studies illustrated that the released drugs were able to diffuse through agar medium, inhibiting MTZ sensitive Bacteroides fragilis. The selected MTZ matrix tablets (F1-F6) had zones of inhibition paralleling those of the marketed formulation. PMID:21696349

Ahmad, Mohammad Zaki; Akhter, Sohail; Ahmad, Iqbal; Rahman, Mahfoozur; Anwar, Mohammad; Jain, Gourav K; Ahmad, Farhan J; Khar, Roop Krishen

2011-09-01

84

In vitro and in vivo evaluation of guar gum matrix tablets for oral controlled release of water-soluble diltiazem hydrochloride.  

PubMed

The objective of the study was to develop guar gum matrix tablets for oral controlled release of water-soluble diltiazem hydrochloride. Matrix tablets of diltiazem hydrochloride, using various viscosity grades of guar gum in 2 proportions, were prepared by wet granulation method and subjected to in vitro drug release studies. Diltiazem hydrochloride matrix tablets containing either 30% wt/wt low-viscosity (LM1), 40% wt/wt medium-viscosity (MM2), or 50% wt/wt high-viscosity (HM2) guar gum showed controlled release. The drug release from all guar gum matrix tablets followed first-order kinetics via Fickian-diffusion. Further, the results of in vitro drug release studies in simulated gastrointestinal and colonic fluids showed that HM2 tablets provided controlled release comparable with marketed sustained release diltiazem hydrochloride tablets (D-SR tablets). Guar gum matrix tablets HM2 showed no change in physical appearance, drug content, or in dissolution pattern after storage at 40 degrees C/relative humidity 75% for 6 months. When subjected to in vivo pharmacokinetic evaluation in healthy volunteers, the HM2 tablets provided a slow and prolonged drug release when compared with D-SR tablets. Based on the results of in vitro and in vivo studies it was concluded that that guar gum matrix tablets provided oral controlled release of water-soluble diltiazem hydrochloride. PMID:16353958

Al-Saidan, Saleh M; Krishnaiah, Yellela S R; Patro, Srinivas S; Satyanaryana, Vemulapalli

2005-01-01

85

Floating Node Method and Virtual Crack Closure Technique for Modeling Matrix Cracking-Delamination Interaction  

NASA Technical Reports Server (NTRS)

A novel approach is proposed for high-fidelity modeling of progressive damage and failure in composite materials that combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. In this study, the approach is applied to the modeling of delamination migration in cross-ply tape laminates. Delamination, matrix cracking, and migration are all modeled using fracture mechanics based failure and migration criteria. The methodology proposed shows very good qualitative and quantitative agreement with experiments.

DeCarvalho, N. V.; Chen, B. Y.; Pinho, S. T.; Baiz, P. M.; Ratcliffe, J. G.; Tay, T. E.

2013-01-01

86

Floating Node Method and Virtual Crack Closure Technique for Modeling Matrix Cracking-Delamination Migration  

NASA Technical Reports Server (NTRS)

A novel approach is proposed for high-fidelity modeling of progressive damage and failure in composite materials that combines the Floating Node Method (FNM) and the Virtual Crack Closure Technique (VCCT) to represent multiple interacting failure mechanisms in a mesh-independent fashion. In this study, the approach is applied to the modeling of delamination migration in cross-ply tape laminates. Delamination, matrix cracking, and migration are all modeled using fracture mechanics based failure and migration criteria. The methodology proposed shows very good qualitative and quantitative agreement with experiments.

DeCarvalho, Nelson V.; Chen, B. Y.; Pinho, Silvestre T.; Baiz, P. M.; Ratcliffe, James G.; Tay, T. E.

2013-01-01

87

Introduction of Sustained Release Opipramol Dihydrochloride Matrix Tablets as a New Approach in the Treatment of Depressive Disorders  

PubMed Central

Opipramol 2-HCl (OP) is used for therapy of general somatoform and anxiety disorders. Conventional tablets in the market contain 50 mg OP to be used once or up to three times a day in effective treatment of depression in mild. In case of serious depressive disorders, OP may be administired up to 300 mg a day. Decrease in frequency of high dose administration via sustained drug release would reduce incidence of symptoms of intoxication in long-term use of OP. With this aim, OP matrix tablets containing 100 mg were prepared by direct compression method to be used once a day to provide patient compliance and constant blood level, consequently to decrease side effects. Two concentrations of polymers (10% and 20%): hydroxypropylcellulose (HPC) and hydroxypropyl methylcellulose (HPMC), sodium alginate (NaAlg), xanthan gum (XG) and Carbopol®941 (C941) were used in preparation of matrix tablets. Drug release study were performed in distilled water, pH1.2 HCl buffer and pH7.4 phosphate buffer solutions according to the Method II in USP 29. Two commercial tablets containing 50 mg OP available in Turkish market were used for comparison. Kinetic models of release patterns from tablets were evaluated. Drug release was displayed slower to faster pattern in order of formulations containing C941, HPMC and HPC. Drug release was significantly faster in tablets of 10% polymers than those of 20%. NaAlg and XG were insufficient to sustain drug release. The most sustaining drug release effect at the lowest polymer concentration was obtained with C941. Drug release from matrix tablets containing 10% C941 was determined as 58.2%, 52.4 and 57.0% in related dissolution mediums above after 8 hours, respectively. However, HPMC and HPC sustained drug release at 20% concentration. As a result, Carbopol® 941, HPMC and HPC can be suggested as suitable to prepare matrix tablets of OP.

Gonullu, Umit; Uner, Melike; Yener, Gulgun; Alt?nkurt, Turan

2006-01-01

88

Introduction of sustained release opipramol dihydrochloride matrix tablets as a new approach in the treatment of depressive disorders.  

PubMed

Opipramol 2-HCl (OP) is used for therapy of general somatoform and anxiety disorders. Conventional tablets in the market contain 50 mg OP to be used once or up to three times a day in effective treatment of depression in mild. In case of serious depressive disorders, OP may be administired up to 300 mg a day. Decrease in frequency of high dose administration via sustained drug release would reduce incidence of symptoms of intoxication in long-term use of OP. With this aim, OP matrix tablets containing 100 mg were prepared by direct compression method to be used once a day to provide patient compliance and constant blood level, consequently to decrease side effects. Two concentrations of polymers (10% and 20%): hydroxypropylcellulose (HPC) and hydroxypropyl methylcellulose (HPMC), sodium alginate (NaAlg), xanthan gum (XG) and Carbopol(®)941 (C941) were used in preparation of matrix tablets. Drug release study were performed in distilled water, pH1.2 HCl buffer and pH7.4 phosphate buffer solutions according to the Method II in USP 29. Two commercial tablets containing 50 mg OP available in Turkish market were used for comparison. Kinetic models of release patterns from tablets were evaluated. Drug release was displayed slower to faster pattern in order of formulations containing C941, HPMC and HPC. Drug release was significantly faster in tablets of 10% polymers than those of 20%. NaAlg and XG were insufficient to sustain drug release. The most sustaining drug release effect at the lowest polymer concentration was obtained with C941. Drug release from matrix tablets containing 10% C941 was determined as 58.2%, 52.4 and 57.0% in related dissolution mediums above after 8 hours, respectively. However, HPMC and HPC sustained drug release at 20% concentration. As a result, Carbopol® 941, HPMC and HPC can be suggested as suitable to prepare matrix tablets of OP. PMID:23675002

Gönüllü, Umit; Uner, Melike; Yener, Gülgün; Alt?nkurt, Turan

2006-12-01

89

Preparation and in vitro evaluation of guar gum based triple-layer matrix tablet of diclofenac sodium  

PubMed Central

The objective of the present study was to design an oral controlled drug delivery system for sparingly soluble diclofenac sodium (DCL) using guar gum as triple-layer matrix tablets. Matrix tablet granules containing 30% (D1), 40% (D2) or 50% (D3) of guar gum were prepared by the conventional wet granulation technique. Matrix tablets of diclofenac sodium were prepared by compressing three layers one by one. Centre layer of sandwich like structure was incorporated with matrix granules containing DCL which was covered on either side by guar gum granule layers containing either 70, 80 or 87% of guar gum as release retardant layers. The tablets were evaluated for hardness, thickness, drug content, and drug release studies. To ascertain the kinetics of drug release, the dissolution profiles were fitted to various mathematical models. The in vitro drug release from proposed system was best explained by the Hopfenberg model indicating that the release of drug from tablets displayed heterogeneous erosion. D3G3, containing 87% of guar gum in guar gum layers and 50% of guar gum in DCL matrix granule layer was found to provide the release rate for prolonged period of time. The results clearly indicate that guar gum could be a potential hydrophilic carrier in the development of oral controlled drug delivery systems.

Chavda, H.V.; Patel, M.S.; Patel, C.N.

2012-01-01

90

Formulation and roentgenographic studies of naproxen-pectin-based matrix tablets for colon drug delivery.  

PubMed

A study has been carried out to assess the potential use of pectin in combination with two added hydrocolloids, i.e., hydroxy-propyl-methyl cellulose and hydroxyethyl cellulose in varied concentrations and coated with ethyl cellulose and cellulose acetate phthalate. The results of in vitro drug release showed that the matrix tablets prepared with pectin, hydroxy ethyl cellulose (20 percent) when coated with ethyl cellulose and cellulose acetate phthalate were found to be 63.0 percent, 8.4 percent, and 4.5 percent, respectively, in after eight hours during drug release study period. These results were confirmed with the results of roentgenographic studies in nine healthy human volunteers to find the shape and integrity of the dosage form. The X-ray photographs revealed that the enteric-coated tablet was visible only up to 5.5 hours and at the end of eighth hour, the photograph has not shown any presence of tablet indicating the loss of shape and size by the microflora present in the colon region. So, the results of in vitro and roentgenographic studies revealed that pectin, hydroxy ethyl cellulose (20 percent) base coated with ethyl cellulose and cellulose acetate phthalate was found to be a promising carrier for naproxen to colon. PMID:15482652

Rao, K Purushotham; Prabhashankar, B; Kumar, Ashok; Khan, Azeemuddin; Biradar, S S; Srishail, S Patil; Satyanath, B

2003-01-01

91

Formulation and roentgenographic studies of naproxen-pectin-based matrix tablets for colon drug delivery.  

PubMed Central

A study has been carried out to assess the potential use of pectin in combination with two added hydrocolloids, i.e., hydroxy-propyl-methyl cellulose and hydroxyethyl cellulose in varied concentrations and coated with ethyl cellulose and cellulose acetate phthalate. The results of in vitro drug release showed that the matrix tablets prepared with pectin, hydroxy ethyl cellulose (20 percent) when coated with ethyl cellulose and cellulose acetate phthalate were found to be 63.0 percent, 8.4 percent, and 4.5 percent, respectively, in after eight hours during drug release study period. These results were confirmed with the results of roentgenographic studies in nine healthy human volunteers to find the shape and integrity of the dosage form. The X-ray photographs revealed that the enteric-coated tablet was visible only up to 5.5 hours and at the end of eighth hour, the photograph has not shown any presence of tablet indicating the loss of shape and size by the microflora present in the colon region. So, the results of in vitro and roentgenographic studies revealed that pectin, hydroxy ethyl cellulose (20 percent) base coated with ethyl cellulose and cellulose acetate phthalate was found to be a promising carrier for naproxen to colon.

Rao, K. Purushotham; Prabhashankar, B.; Kumar, Ashok; Khan, Azeemuddin; Biradar, S. S.; Srishail, S. Patil; Satyanath, B.

2003-01-01

92

Prolonged release matrix tablet of pyridostigmine bromide: formulation and optimization using statistical methods.  

PubMed

The aim of this study was to design and optimize a prolonged release matrix formulation of pyridostigmine bromide, an effective drug in myasthenia gravis and poisoning with nerve gas, using hydrophilic - hydrophobic polymers via D-optimal experimental design. HPMC and carnauba wax as retarding agents as well as tricalcium phosphate were used in matrix formulation and considered as independent variables. Tablets were prepared by wet granulation technique and the percentage of drug released at 1 (Y(1)), 4 (Y(2)) and 8 (Y(3)) hours were considered as dependent variables (responses) in this investigation. These experimental responses were best fitted for the cubic, cubic and linear models, respectively. The optimal formulation obtained in this study, consisted of 12.8 % HPMC, 24.4 % carnauba wax and 26.7 % tricalcium phosphate, had a suitable prolonged release behavior followed by Higuchi model in which observed and predicted values were very close. The study revealed that D-optimal design could facilitate the optimization of prolonged release matrix tablet containing pyridostigmine bromide. Accelerated stability studies confirmed that the optimized formulation remains unchanged after exposing in stability conditions for six months. PMID:22713949

Bolourchian, Noushin; Rangchian, Maryam; Foroutan, Seyed Mohsen

2012-07-01

93

In vitro release kinetics and bioavailability of gastroretentive cinnarizine hydrochloride tablet.  

PubMed

An oral sustained release dosage form of cinnarizine HCl (CNZ) based on gastric floating matrix tablets was studied. The release of CNZ from different floating matrix formulations containing four viscosity grades of hydroxypropyl methylcellulose, sodium alginate or polyethylene oxide, and gas-forming agent (sodium bicarbonate or calcium carbonate) was studied in simulated gastric fluid (pH 1.2). CNZ release data from the matrix tablets were analyzed kinetically using Higuchi, Peppas, Weibull, and Vergnaud models. From water uptake, matrix erosion studies, and drug release data, the overall release mechanism can be explained as a result of rapid hydration of polymer on the surface of the floating tablet and formation of a gel layer surrounding the matrix that controls water penetration into its center. On the basis of in vitro release data, batch HP1 (CNZ, HPMC-K100LV, SBC, LTS, and MgS) was subjected to bioavailability studies in rabbits and was compared with CNZ suspension. It was concluded that the greater bioavailability of HP1 was due to its longer retention in the gastric environment of the test animal. Batch no. HP1 of floating tablet in rabbits demonstrated that the floating tablet CNZ could be a 24-h sustained release formulation. PMID:20182827

Nagarwal, Ramesh C; Ridhurkar, Devendra N; Pandit, J K

2010-03-01

94

Formulation and in vitro, in vivo evaluation of extended- release matrix tablet of zidovudine: influence of combination of hydrophilic and hydrophobic matrix formers.  

PubMed

The aim of the present study was to prepare and characterize extended-release matrix tablets of zidovudine using hydrophilic Eudragit RLPO and RSPO alone or their combination with hydrophobic ethyl cellulose. Release kinetics was evaluated by using United States Pharmacopeia (USP)-22 type I dissolution apparatus. Scanning electron microscopy was used to visualize the effect of dissolution medium on matrix tablet surface. Furthermore, the in vitro and in vivo newly formulated sustained-release zidovudine tablets were compared with conventional marketed tablet (Zidovir, Cipla Ltd, Mumbai, India). The in-vitro drug release study revealed that either Eudragit preparation was able to sustain the drug release only for 6 hours (94.3% +/- 4.5% release). Combining Eudragit with ethyl cellulose sustained the drug release for 12 hours (88.1% +/- 4.1% release). Fitting the in vitro drug release data to Korsmeyer equation indicated that diffusion along with erosion could be the mechanism of drug release. In vivo investigation in rabbits showed sustained-release pharmacokinetic profile of zidovudine from the matrix tablets formulated using combination of Eudragits and ethylcellulose. In conclusion, the results suggest that the developed sustained-release tablets of zidovudine could perform therapeutically better than conventional dosage forms, leading to improve efficacy and better patient compliance. PMID:16584139

Kuksal, Atul; Tiwary, Ashok K; Jain, Narendra K; Jain, Subheet

2006-01-01

95

Development and evaluation of chitosan based oral controlled matrix tablets of losartan potassium  

PubMed Central

Aim and Background: The novelty of the present study was to control the release profile of matrix tablets of losartan potassium prepared by using different concentrations of chitosan and trisodium citrate as cross-linking agent with combination of various release retardant polymers. Materials and Methods: Twelve formulations were prepared using HPMC K100M, carbopol 934P, and xanthan gum as polymers. Matrix tablets were prepared by wet granulation technique. The granules were subjected to precompression parameters such as angle of repose, loose bulk density, tapped bulk density, compressibility index. Tablets were evaluated for weight variation, hardness, drug content, in-vitro dissolution, stability studies, respectively. Drug -polymer compatibility studies were determined by FTIR spectroscopy. Further stability studies were carried out for 3months in accelerated conditions at 40°C and 75%RH. The granules of all formulations exhibited good flow and compressibility. In-vitro dissolution studies were carried out for 24 h using 0.1 N HCl for the first 2 h and pH 6.8 phosphate buffers for the remaining 22h. Results: It was found that among the 12 formulations F11 and F12 showed good dissolution profile to control the drug release. The release data was fitted to various mathematical models such as, Higuchi, Korsmeyer, first-order, and zero-order to evaluate the kinetics and the drug release. The drug release follows zero-order kinetics and the mechanism was found to be diffusion controlled and Case II transport. FT-IR spectroscopic studies revealed no interaction between drug and polymer. The stability studies indicated that F11 and F12 formulations were stable for 3months. Conclusion: The above results concluded that by combining different classes of polymers an acceptable release profile can be obtained in the fluctuating in vivo environment.

Rao, Tallapaneni Vishnuvardhan; Kumar, GB Kiran; Ahmed, Mohammed Gulzar; Joshi, Vedamurthy

2012-01-01

96

Influence of Organic Acids on Diltiazem HCl Release Kinetics from Hydroxypropyl Methyl Cellulose Matrix Tablets  

PubMed Central

The matrix tablets of diltiazem hydrochloride were prepared by direct compression using hydroxypropyl methyl cellulose (HPMC) and various amounts (2.5%, 5.0%, 10% and 20%) of citric acid, malic acid and succinic acid. The characterization of physical mixture of drug and organic acids was performed by Infra-red spectroscopy. An organic acid was incorporated to set up a system bringing about gradual release of this drug. The influence of organic acids on the release rate were described by the Peppas equation: M t /M? = Kt n and Higuchi’s equation: Q t = K1t1/2. The addition of organic acids and the pH value of medium could notably influence the dissolution behavior and mechanism of drug-release from matrices. Increasing amounts of organic acid produced an increase in drug release rate, which showed a good linear relationship between contents of organic acid and drug accumulate release (%) in phosphate buffer, pH 7.4. The drug release increased significantly (P < 0.05) with use of succinic acid in tablet formulation. Increasing amounts of succinic acid above 10% produced decreasing values of n and increasing values of k, in a linear relationship, which indicated there was a burst release of drug from the matrix. Optimized formulations are found to be stable upon 3-month study.

Sateesha, SB; Rajamma, AJ; Narode, MK; Vyas, BD

2010-01-01

97

Drug Release Kinetics and Front Movement in Matrix Tablets Containing Diltiazem or Metoprolol/?-Carrageenan Complexes  

PubMed Central

In this work we investigated the moving boundaries and the associated drug release kinetics in matrix tablets prepared with two complexes between ?-carrageenan and two soluble model drugs, namely, diltiazem HCl and metoprolol tartrate aiming at clarifying the role played by drug/polymer interaction on the water uptake, swelling, drug dissolution, and drug release performance of the matrix. The two studied complexes released the drug with different mechanism indicating two different drug/polymer interaction strengths. The comparison between the drug release behaviour of the complexes and the relevant physical mixtures indicates that diltiazem gave rise to a less soluble and more stable complex with carrageenan than metoprolol. The less stable metoprolol complex afforded an erodible matrix, whereas the stronger interaction between diltiazem and carrageenan resulted in a poorly soluble, slowly dissolving matrix. It was concluded that the different stability of the studied complexes affords two distinct drug delivery systems: in the case of MTP, the dissociation of the complex, as a consequence of the interaction with water, affords a classical soluble matrix type delivery system; in the case of DTZ, the dissolving/diffusing species is the complex itself because of the very strong interaction between the drug and the polymer.

Bonferoni, Maria Cristina; Colombo, Paolo; Zanelotti, Laura; Caramella, Carla

2014-01-01

98

Tablet boudinage of an anhydrite layer in rock-salt matrix: Results from thermomechanical experiments  

NASA Astrophysics Data System (ADS)

A single competent layer of anhydrite, embedded in a matrix of incompetent rock salt, was deformed in a flattening type of bulk deformation at temperature, T = 345 °C, strain rate, ? = 10 -7 s -1, to a maximum finite strain, e Z = -30%. As the anhydrite layer was oriented perpendicular to the main shortening direction, Z, the layer underwent equal layer-parallel extension in all directions resulting in tablet-shaped boudins. Boudinage results from tensile fracture of anhydrite. The rock-salt matrix, on the other hand, behaved viscously. Crystal plastic deformation of halite was accommodated by slip on {110}<110> which led to formation and rotation of subgrains and a 001-maximum parallel to the principal shortening axis, Z. An axisymmetric texture of halite, however, is present only in high-strain domains at the contact to the anhydrite layer where the differential stress, obtained from subgrain size of halite, reaches maximum values of ca. 6 MPa. Subgrains remote from the anhydrite layer yielded 2-3 MPa, which is consistent with the flow stress recorded by the load cell of the machine. The non-isometric shape of the tablet boudins in plan-view is indicated by the ratio between long and short axis ( R = 1.2-1.9), and can be explained by the interaction of concentric and radial tensile fractures. Both the mean diameter of the tablet boudins in plan-view, W a, and the number of boudins, N, show a linear relation to the layer thickness. Progressive finite strain results in a higher number and a smaller mean diameter of the boudins. The thickness of the boudins, H f, is almost the same like the initial layer thickness, H i, while the aspect ratio ( W d = W a/ H f) decreases with finite strain. The mean W d values obtained from all runs are ranging from ca. 0.8 to ca. 1.5. This range is much lower than the aspect ratio of boudins in viscous or brittle/viscous layers, but is similar to the aspect ratio expected from fracture-saturation models. The aspect ratio of the tablet-shaped anhydrite boudins is further consistent with aspect ratios published so far for tensile-fracture boudins which developed in a plane or constrictional type of bulk deformation.

Zulauf, J.; Zulauf, G.; Hammer, J.; Zanella, F.

2011-12-01

99

In vitro controlled release of colon targeted mesalamine from compritol ATO 888 based matrix tablets using factorial design  

PubMed Central

A controlled release matrix formulation for mesalamine was designed and developed to achieve a 24 h release profile. Using compritol 888 ATO (glyceryl behenate) as an inert matrix-forming agent to control the release of mesalamine, formulation granules containing the solid dispersions were investigated. Pectin, a polysaccharide, was used as bacterial dependent polymer for colon targeting. The matrix tablets for these formulations were prepared by direct compression and their in vitro release tests were carried out. A 32 full factorial design was used for optimization by taking the amounts of glyceryl behenate (X1) and pectin (X2) as independent variables and percentage drug released at 2 (Q2), 16 (Q16) and 24 (Q24) h as dependent variables. Drug release from the matrix tablets formulations lasted for over 24 h. Images of the tablet surface and cross-section were characterized by scanning electron microscopy to show the formed pores and channels in the matrices. These may provide the release pathway for the inner embedded drugs. The co-mixing of polysaccharide pectin, into the waxy matrices played a meaningful role in targeting the tablets to colon. The drug release from the novel formulation may be attributed to the diffusion-controlled mechanism. The results of the full factorial design indicated that an optimum amount of compritol ATO 888 and a high amount of pectin favors the colon targeting and controlled release of mesalamine from dosage form.

Patel, J.K.; Patel, N.V.; Shah, S.H.

2009-01-01

100

In vitro Evaluation of the Effect of Combination of Hydrophilic and Hydrophobic Polymers on Controlled Release Zidovudine Matrix Tablets  

PubMed Central

The aim of the present study was to prepare and characterize controlled-release matrix tablets of zidovudine using hydrophilic HPMC K4 M or Carbopol 934 alone or in combination with hydrophobic ethyl cellulose. Release kinetics was evaluated by using USP XXIV dissolution apparatus No.2 (paddle) type. Scanning electron microscopy was used to visualize the effect of dissolution medium on matrix tablet surface. The in vitro results of controlled – release zidovudine tablets were compared with conventional marketed tablet Zidovir. The in vitro drug release study revealed that HPMC K4 M or Carbopol 934 preparation was able to sustain the drug release near to 6 hours. Combining HPMC K4 M or Carbopol 934 with ethyl cellulose sustained the drug release for nearly 12 h. The in vitro evaluation showed that the drug release may be by diffusion along with erosion. Results suggest that the developed controlled-release tablets of zidovudine could perform therapeutically better than marketed dosage forms, leading to improve efficacy, controlling the release and better patient compliance.

Ganesh, S.; Radhakrishnan, M.; Ravi, M.; Prasannakumar, B.; Kalyani, J.

2008-01-01

101

The Influence of the Compression Force on Zidovudine Release from Matrix Tablets  

PubMed Central

The aim of the present work is the study of different zidovudine (AZT) formulations containing polymers (both cellulosic and acrylic), in order to evaluate the influence of the compression force on the antiviral release from the matrix tablets. The results evidenced that the formulations compressed at 500 and 1,000 MPa exhibit a higher hardness than those prepared at 100 MPa. The effect of the compression force on the drug release was analyzed and a statistically significant difference was observed (P?

Santos, Jucimary V.; Batista de Carvalho, Luis A. E.

2010-01-01

102

Controlled Release Hydrophilic Matrix Tablet Formulations of Isoniazid: Design and In Vitro Studies  

PubMed Central

The aim of the present investigation was to develop oral controlled release matrix tablet formulations of isoniazid using hydroxypropyl methylcellulose (HPMC) as a hydrophilic release retardant polymer and to study the influence of various formulation factors like proportion of the polymer, polymer viscosity grade, compression force, and release media on the in vitro release characteristics of the drug. The formulations were developed using wet granulation technology. The in vitro release studies were performed using US Pharmacopoeia type 1 apparatus (basket method) in 900 ml of pH 7.4 phosphate buffer at 100 rpm. The release kinetics was analyzed using Korsmeyer–Peppas model. The release profiles were also analyzed using statistical method (one-way analysis of variance) and f2 metric values. The release profiles found to follow Higuchi’s square root kinetics model irrespective of the polymer ratio and the viscosity grade used. The results in the present investigation confirm that the release rate of the drug from the HPMC matrices is highly influenced by the drug/HPMC ratio and viscosity grade of the HPMC. Also, the effect of compression force and release media was found to be significant on the release profiles of isoniazid from HPMC matrix tablets. The release mechanism was found to be anomalous non-Fickian diffusion in all the cases. In the present investigation, a series of controlled release formulations of isoniazid were developed with different release rates and duration so that these formulations could further be assessed from the in vivo bioavailability studies. The formulations were found to be stable and reproducible.

Saha, Ranendra N.

2008-01-01

103

Fabrication of Triple-Layer Matrix Tablets of Venlafaxine Hydrochloride Using Xanthan Gum  

Microsoft Academic Search

The objective of present investigation was to develop venlafaxine hydrochloride-layered tablets for obtaining sustained drug\\u000a release. The tablets containing venlafaxine hydrochloride 150 mg were prepared by wet granulation technique using xanthan\\u000a gum in the middle layer and barrier layers. The granules and tablets were characterized. The in vitro drug dissolution study was conducted in distilled water. The tablets containing two lower

Mukesh C. Gohel; Shital H. Bariya

2009-01-01

104

Photoimages and the release characteristics of lipophilic matrix tablets containing highly water-soluble potassium citrate with high drug loadings.  

PubMed

Two types of the carnauba wax-based lipophilic matrix tablet using spray-dried granules (SDT) or directly compressible powdered mixtures (DCT) were prepared for sustained release. The model drug was a highly water-soluble potassium citrate and loaded about 74% of the total tablet weight. The SDT slowly eroded and disintegrated during the release study without showing sustained release when the hydrophilic excipients were added. In contrast, the DCT was more efficient for sustained release. The release rate decreased with increasing carnauba wax concentration. In particular, the sustained release rate was markedly pronounced when the lipophilic stearyl alcohol and stearic acid were combined with the carnauba wax. The surface of the intact DCT appeared to be smooth and rusty. The DCT rose to the surface from the bottom of the vessel during the release test, and numerous pores and cracks with no signs of disintegration were also observed after the release test. The release profile was dependent on the formulation composition and preparation method of the matrix tablet. Diffusion-controlled leaching through the channels of the pores and cracks of the lipophilic matrix tablet (DCT) is a key to the sustained release. PMID:17532156

Cao, Qing-Ri; Kim, Tae-Wan; Lee, Beom-Jin

2007-07-18

105

An innovative matrix controlling drug delivery produced by thermal treatment of DC tablets containing polycarbophil and ethylcellulose.  

PubMed

An innovative matrix, produced by thermal treatment on direct compression (DC) tablets containing polycarbophil (POL) and ethylcellulose (EC), identified as matrix forming polymers, and able to control the release of diltiazem hydrochloride, was developed. At pH 7.2, 72 ± 1.2% (w/w) of drug loaded was released in 25 h, mostly at constant rate. This swellable and unerodible matrix controls drug release by an anomalous transport mechanism. The modifications induced by the thermal treatment are irreversible and can be used to control and characterize the matrix. A 3-component constrained mixture design allowed the investigation of the experimental domain in which the matrix forms and the computation of a mathematical model that can be used to optimize the formulation properties. The release rate can be modulated (0.032-0.064% drug released/min) through the choice of suitable treatment conditions and tablet composition. The maximum amount of diltiazem hydrochloride released by zero-order kinetics, at the lowest release rate, occurs for POL:EC ratio in the range of 1:1-2:3 with 20-30% of diluent. The tablets are able to load up to 50% (w/w) of diltiazem hydrochloride without losing their properties. A stability study performed on a selected formulation containing DTZ showed stability for at least 2.7 years at RT conditions. PMID:24144954

Caviglioli, Gabriele; Baldassari, Sara; Cirrincione, Paola; Russo, Eleonora; Parodi, Brunella; Gatti, Paolo; Drava, Giuliana

2013-12-15

106

Biphasic release of indomethacin from HPMC/pectin/calcium matrix tablet: II. Influencing variables, stability and pharmacokinetics in dogs.  

PubMed

The pectin/calcium interaction, which is the basis for biphasic release of indomethacin from the HPMC/pectin/calcium chloride matrix tablet, is susceptible to influence of a variety of variables that is supposed to be encountered by the oral route. In this study, the effect of influencing variables on biphasic release characteristics, the stability and the pharmacokinetics of the hybrid matrix tablet were investigated. An increasing tendency of the overall release rate was observed from pH 1.2 to 7.4. The power law correlation n values increased with pH, while the release lag time or 10% release time (T0.1) decreased at pH 6.8 and 7.4. Ionic strength in the release media also influenced the biphasic release significantly at sodium chloride levels of over 0.5%. Obvious increase in overall release rate was observed at sodium chloride level of 0.9% with an n value of 1.20 and a T0.1 of 3.4h. At sodium chloride levels of over 2%, the pectin/calcium interaction was disrupted resulting in very fast release of indomethacin. Release in gradient pH media was similar to that in pH 6.8 citrate buffer. When pectinase (Pectinex Ultra SP-L) was added into the release medium in 22.2 pg/ml or over, obvious triggering on drug release was observed. The stress testing showed increased release at extreme relative humidity of 92.5%. Both accelerated testing for 6m and long-term testing for 12 m affirmed fine stability, especially in release characteristics. Pharmacokinetic study in dogs gave Tmax/Cmax of 4h/604 ng/ml and 3h/1662 ng/ml for HPMC/pectin/calcium and HPMC/pectin tablet, respectively. The plasma indomethacin level of the calcium-containing tablet was maintained at a much lower level for 3h with a MRT of 7.13 h, longer than 3.97 and 5.61 h for indomethacin crude drug and HPMC/pectin tablet, confirming delayed absorption. The AUC of the HPMC/pectin/calcium tablet was lower than that of the HPMC/pectin tablet and indomethacin crude drug showing incomplete absorption. It is concluded that the HPMC/pectin/calcium matrix tablet is potentially useful for colon-specific drug delivery. PMID:17988844

Wu, Baojian; Deng, Daoyin; Lu, Yi; Wu, Wei

2008-05-01

107

Sustained release of a water-soluble drug from alginate matrix tablets prepared by wet granulation method.  

PubMed

Alginate matrix tablet of diltiazem hydrochloride (DTZ), a water-soluble drug, was prepared using sodium alginate (SAL) and calcium gluconate (CG) by the conventional wet granulation method for sustained release of the drug. The effect of formulation variables like SAL/CG ratio, drug load, microenvironmental pH modulator, and processing variable like compression force on the extent of drug release was examined. The tablets prepared with 1:2 w/w ratio of SAL/CG produced the most sustained release of the drug extending up to 13.5 h. Above and below this ratio, the drug release was faster. The drug load and the hardness of the tablets produced minimal variation in drug release. The addition of alkaline or acidic microenvironmental modulators did not extend the release; instead, these excipients produced somewhat faster release of diltiazem. This study revealed that proper selection of SAL/CG ratio is important to produce alginate matrix tablet by wet granulation method for sustained release of DTZ. PMID:19911286

Mandal, Sanchita; Basu, Sanat Kumar; Sa, Biswanath

2009-01-01

108

Conceptuation, formulation and evaluation of sustained release floating tablets of captopril compression coated with gastric dispersible hydrochlorothiazide using 23 factorial design  

PubMed Central

Ambulatory blood pressure monitoring is regarded as the gold standard for hypertensive therapy in non-dipping hypertension patients. A novel compression coated formulation of captopril and hydrochlorothiazide (HCTZ) was developed in order to improve the efficacy of antihypertensive therapy considering the half-life of both drugs. The synergistic action using combination therapy can be effectively achieved by sustained release captopril (t1/2= 2.5 h) and fast releasing HCTZ (average t1/2= 9.5 h). The sustained release floating tablets of captopril were prepared by using 23 factorial design by employing three polymers i.e., ethyl cellulose (EC), carbopol and xanthan gum at two levels. The formulations (CF1-CF8) were optimized using analysis of variance for two response variables, buoyancy and T50%. Among the three polymers employed, the coefficients and P values for the response variable buoyancy and T50% using EC were found to be 3.824, 0.028 and 0.0196, 0.046 respectively. From the coefficients and P values for the two response variables, formulation CF2 was optimized, which contains EC polymer alone at a high level. The CF2 formulation was further compression coated with optimized gastric dispersible HCTZ layer (HF9). The compression coated tablet was further evaluated using drug release kinetics. The Q value of HCTZ layer is achieved within 20 min following first order release whereas the Q value of captopril was obtained at 6.5 h following Higuchi model, from which it is proved that rapid release HCTZ and slow release of captopril is achieved. The mechanism of drug release was analyzed using Peppas equation, which showed an n >0.90 confirming case II transportation mechanism for drug release.

Sirisha, Pathuri Lakshmi; Babu, Govada Kishore; Babu, Puttagunta Srinivasa

2014-01-01

109

Conceptuation, formulation and evaluation of sustained release floating tablets of captopril compression coated with gastric dispersible hydrochlorothiazide using 2(3) factorial design.  

PubMed

Ambulatory blood pressure monitoring is regarded as the gold standard for hypertensive therapy in non-dipping hypertension patients. A novel compression coated formulation of captopril and hydrochlorothiazide (HCTZ) was developed in order to improve the efficacy of antihypertensive therapy considering the half-life of both drugs. The synergistic action using combination therapy can be effectively achieved by sustained release captopril (t1/2= 2.5 h) and fast releasing HCTZ (average t1/2= 9.5 h). The sustained release floating tablets of captopril were prepared by using 2(3) factorial design by employing three polymers i.e., ethyl cellulose (EC), carbopol and xanthan gum at two levels. The formulations (CF1-CF8) were optimized using analysis of variance for two response variables, buoyancy and T50%. Among the three polymers employed, the coefficients and P values for the response variable buoyancy and T50% using EC were found to be 3.824, 0.028 and 0.0196, 0.046 respectively. From the coefficients and P values for the two response variables, formulation CF2 was optimized, which contains EC polymer alone at a high level. The CF2 formulation was further compression coated with optimized gastric dispersible HCTZ layer (HF9). The compression coated tablet was further evaluated using drug release kinetics. The Q value of HCTZ layer is achieved within 20 min following first order release whereas the Q value of captopril was obtained at 6.5 h following Higuchi model, from which it is proved that rapid release HCTZ and slow release of captopril is achieved. The mechanism of drug release was analyzed using Peppas equation, which showed an n >0.90 confirming case II transportation mechanism for drug release. PMID:25006552

Sirisha, Pathuri Lakshmi; Babu, Govada Kishore; Babu, Puttagunta Srinivasa

2014-04-01

110

Ultrasound Transmission Technique as a Potential Tool for Physical Evaluation of Monolithic Matrix Tablets  

PubMed Central

The aim of this study was to investigate the effects of tablet porosity and particle size fraction of compacted Starch acetate powders, with and without model drug caffeine, on acoustic properties of tablets. The ultrasound velocity was determined from the transmission measurements. Tablets of starch acetate (SA DS 2.7) powder with two particle size fractions of 0–53 and 0–710 ?m were compressed with a compaction simulator. Porosities of tablets varied in the range from 12% to 43% for both particle size fractions. Strong associations were found between the ultrasound velocity and physical properties of the tablets such as porosity and particle size fraction. Interestingly, ultrasound velocity was practically insensitive to inclusion of the model drug caffeine with the concentrations used. Based on this study ultrasound transmission method is a potential non-destructive tool for studying structural changes of tablets and other solid dosage forms.

Pajander, J.; Leskinen, J.; Ketolainen, J.; van Veen, B.; Niinimaki, K.; Pirskanen, K.; Poso, A.; Lappalainen, R.

2008-01-01

111

Formualtion and evaluation of floating drug delivery system containing clarithromycin for Helicobacter pylori.  

PubMed

Floating matrix tablets are designed to prolong the gastric residence time after oral administration, at a particular site and controlling the release of drug especially useful for achieving controlled plasma level as well as improving bioavailability. With this objective, floating dosage form containing clarithromycin as drug was designed for the treatment of Helicobacter pylori. Tablets containing hydroxypropylmethylcellulose (HPMC), drug and different additives were compressed using wet granulation and D-optimal design technique. The study shows that tablet composition and mechanical strength have great influence on the floating properties and drug release. Incorporation of gas-generating agent together with polymer improved drug release, besides optimal floating (floating lag time < 30 s; total floating time > 10 h). The drug release was sufficiently sustained (more than 8 h) and anomalous diffusion as well as zero-order was confirmed. Optimization of the evaluating parameters with 'design expert' software was employed to get final optimized formulation. The optimized formulation was obtained using 62.5% clarithromycin, 4.95% HPMC K15M, 18.09% HPMC K4M, 12.96% sodium bicarbonate which gave floating lag time < 30 s with a total floating time > 10 h, in vitro release profile very near to the target in vitro release profile and follows anomalous diffusion as well as zero order pattern of release. PMID:17515330

Patel, Sanjay S; Ray, S; Thakur, R S

2006-01-01

112

Sustained Release of a Water-Soluble Drug from Alginate Matrix Tablets Prepared by Wet Granulation Method  

Microsoft Academic Search

Alginate matrix tablet of diltiazem hydrochloride (DTZ), a water-soluble drug, was prepared using sodium alginate (SAL) and\\u000a calcium gluconate (CG) by the conventional wet granulation method for sustained release of the drug. The effect of formulation\\u000a variables like SAL\\/CG ratio, drug load, microenvironmental pH modulator, and processing variable like compression force on\\u000a the extent of drug release was examined. The

Sanchita Mandal; Sanat Kumar Basu; Biswanath Sa

2009-01-01

113

Controlled Release Matrix Tablets of Olanzapine: Influence of Polymers on the In Vitro Release and Bioavailability  

PubMed Central

Controlled-release (CR) tablet formulation of olanzapine was developed using a binary mixture of Methocel® K100 LV-CR and Ethocel® standard 7FP premium by the dry granulation slugging method. Drug release kinetics of CR tablet formulations F1, F2, and F3, each one suitably compressed for 9-, 12-, and 15-kg hardness, were determined in a dissolution media of 0.1 N HCl (pH 1.5) and phosphate buffer (pH 6.8) using type II dissolution apparatus with paddles run at 50 rpm. Ethocel® was found to be distinctly controlling drug release, whereas the hardness of tablets and pH of the dissolution media did not significantly affect release kinetics. The CR test tablets containing 30% Methocel® and 60% Ethocel® (F3) with 12-kg hardness exhibited pH-independent zero-order release kinetics for 24 h. In vivo performance of the CR test tablet and conventional reference tablet were determined in rabbit serum using high-performance liquid chromatography coupled with electrochemical detector. Bioavailability parameters including Cmax, Tmax, and AUC0–48 h of both tablets were compared. The CR test tablets produced optimized Cmax and extended Tmax (P?tablet was calculated as 94%. The manufacturing process employed was reproducible and the CR test tablets were stable for 6 months at 40?±?2°C/75?±?5% relative humidity. It was concluded that the CR test tablet formulation successfully developed may improve tolerability and patient adherence by reducing adverse effects.

Subhan, Fazal; Rauf, Khalid

2010-01-01

114

Wax-matrix tablet for time-dependent colon-specific delivery system of sophora flavescens Aiton: preparation and in vivo evaluation.  

PubMed

A wax-matrix time-dependent colon-specific tablet (WM-TDCS) was studied. Wax-matrix tablet core consisting of semi-synthetic glycerides, as a wax polymeric expanding agent, carboxymethyl starch sodium (CMS-Na), and NaCl was prepared, and Sophora flavescens Aiton (ASF, extracts of traditional Chinese medicine) was used as model drug. The wax-matrix ASF tablets core was coated with Eudragit NE 30 D as the inner coating materials and with Opadry OY-P-7171 as the outer coating materials. The in vitro release behaviors of the coated tablets were examined and then in vivo absorption kinetics of the coated tablets in dogs was further investigated. The volume of the tablet core was markedly increased at 37 degrees C because of the expand effect of polymer semi-synthetic glycerides and CMS-Na. The drug release from WM-TDCS was more stable than TDCS in vitro and in vivo. The lag time of ASF release was also controlled by the thickness of the inner coating layer. In vivo evaluation demonstrated that in vivo lag time of absorption was in a good agreement with in vitro lag time of release. ASF wax-matrix tablets coated with Eudragit NE 30 D and Opadry OY-P-7171 using the regular coating technique could be designed to achieve a lag time of 3 h in the small intestinal tract. PMID:18785039

Zou, Meijuan; Wang, Yue; Xu, Caihong; Cheng, Gang; Ren, Jungang; Wu, Gaolei

2009-02-01

115

Use of hydroxypropyl methylcellulose acetate succinate in an enteric polymer matrix to design controlled-release tablets of amoxicillin trihydrate.  

PubMed

A controlled-release table of amoxicillin trihydrate was developed by use of a matrix formulation based on the enteric polymer hydroxypropyl methylcellulose acetate succinate (HPMCAS). Sustained drug release was shown by in vitro dissolution testing; the polymer could suppress drug release in the presence of gastric pH but could enhance drug release in the presence of small intestinal pH, compared with compacts of pure drug. Grinding or physical mixing of the drug with the polymer, an alteration in normal compaction pressure, or a substitution of other enteric polymers did not markedly affect drug release from compacts. Physicochemical testing of samples confirmed that the method of mixing did not alter powder morphology. An ethanolic granulation procedure was used in the production of final tablets (21 x 10 mm) containing amoxicillin (750 mg), HPMCAS, anhydrous directly compressible lactose, and lubricants. These large tablets showed a promising sustained-release effect in vitro when a variable-pH-shift dissolution procedure was used. However, single-dose studies with a panel of fasting subjects showed that the tablets had a relative bioavailability of only 64.4%. Other pharmacokinetic parameters confirmed a lack of therapeutic advantage of these tablets over an equivalent dose of conventional capsules. PMID:8360849

Hilton, A K; Deasy, P B

1993-07-01

116

Artificial neural networks in the modeling and optimization of aspirin extended release tablets with Eudragit L 100 as matrix substance.  

PubMed

The purpose of the present study was to model the effects of the concentration of Eudragit L 100 and compression pressure as the most important process and formulation variables on the in vitro release profile of aspirin from matrix tablets formulated with Eudragit L 100 as matrix substance and to optimize the formulation by artificial neural network. As model formulations, 10 kinds of aspirin matrix tablets were prepared. The amount of Eudragit L 100 and the compression pressure were selected as causal factors. In vitro dissolution time profiles at 4 different sampling times were chosen as responses. A set of release parameters and causal factors were used as tutorial data for the generalized regression neural network (GRNN) and analyzed using a computer. Observed results of drug release studies indicate that drug release rates vary widely between investigated formulations, with a range of 5 hours to more than 10 hours to complete dissolution. The GRNN model was optimized. The root mean square value for the trained network was 1.12%, which indicated that the optimal GRNN model was reached. Applying the generalized distance function method, the optimal tablet formulation predicted by GRNN was with 5% of Eudragit L 100 and tablet hardness 60N. Calculated difference (f1 2.465) and similarity (f2 85.61) factors indicate that there is no difference between predicted and experimentally observed drug release profiles for the optimal formulation. This work illustrates the potential for an artificial neural network, GRNN, to assist in development of extended release dosage forms. PMID:12916918

Ibri?, Svetlana; Jovanovi?, Milica; Djuri?, Zorica; Parojci?, Jelena; Petrovi?, Slobodan D; Solomun, Ljiljana; Stupar, Biljana

2003-01-01

117

An investigation into the drug release from ibuprofen matrix tablets with ethylcellulose and some poly-acrylate polymers.  

PubMed

This study was performed to achieve sustained-release Ibuprofen matrix tablets with a zero-order release kinetic while most of the previous formulations have shown Higuchi release kinetic. Considering the results from previous studies, ethyl cellulose, Carbopol 934P, Carbopol 974P, and Pemulen TR-1 were used at different amounts for preparation of the tablets by direct compression. The release profiles were studied in a two-stage release test using non-linear regression analysis. Carbopols 934P and 974P could not sustain the release adequately while Pemulen TR-1 had too strong sustaining effect. Therefore, combination formulations were considered and studied. The release profiles of ethyl cellulose formulation and the combination formulation consisting Carbopol 934P and Pemulen TR-1 best fitted in Higuchi model, although the zero-order model was not completely rejected. However, the kinetic model of release from the combination formulation consisting Carbopol 974P and Pemulen TR-1 changed to zero-order indicating the most constant release rate among formulations. This was speculated to be due to some erosion of the gel, as well as some interaction of the hydrophobic chain of Pemulen TR-1 with Ibuprofen. Therefore, this formulation is suggested for directly compressed sustained-release matrix tablets of Ibuprofen with a more constant release rate. PMID:24811808

Tabandeh, Hosseinali; Mortazavi, Seyed Alireza

2014-05-01

118

Microsphere-based once-daily modified release matrix tablets for oral administration in angina pectoris.  

PubMed

The objective of this research was to develop microsphere-based once-daily modified release tablet formulations of diltiazem hydrochloride (DH), a potent calcium channel blocker used in angina pectoris. For this purpose, DH-loaded microspheres were prepared by the solvent evaporation technique using Eudragit RS 100. The effect of variation in the drug/polymer ratio on the physical and release characteristics of the microspheres was investigated. After the selection of the suitable microspheres, tablets were compressed using Compritol 888 ATO, Ludipress and Cellactose 80 as different direct tableting agents and excipients. As a result, modified release tablet formulations of DH-loaded microspheres were designed successfully for oral administration once rather than two or three times a day in angina pectoris. PMID:18465309

Sengel-Türk, Ceyda T; Hasçicek, Canan; Gönül, Nur?in

2008-06-01

119

A novel gastro-floating multiparticulate system for dipyridamole (DIP) based on a porous and low-density matrix core: in vitro and in vivo evaluation.  

PubMed

The study was aimed to develop a novel gastro-floating multiparticulate system based on a porous and low-density matrix core with excellent floatability. The gastro-floating pellets (GFP) were composed of a porous matrix core, a drug loaded layer (DIP and HPMC), a sub-coating layer (HPMC) and a retarding layer (Eudragit(®) NE 30D). The porous matrix cores were evaluated in specific. EC was chosen as the matrix membrane for its rigidity and minimal expansion to large extent. The porous matrix core was achieved by the complete release of the bulk water soluble excipient from the EC coated beads, and mannitol was selected as the optimal water soluble excipient. SEM photomicrographs confirmed the structure of porous matrix cores. The compositions of GFP were investigated and optimized by orthogonal array design. The optimized formulation could sustain the drug release for 12h and float on the dissolution medium for at least 12h without lag time to float. The pharmacokinetic study was conducted in beagle dogs, and the relative bioavailability of the test preparation was 193.11±3.43%. In conclusion, the novel gastro-floating pellets can be developed as a promising approach for the gastro-retentive drug delivery systems. PMID:24368104

Li, Zhao; Xu, Heming; Li, Shujuan; Li, Qijun; Zhang, Wenji; Ye, Tiantian; Yang, Xinggang; Pan, Weisan

2014-01-30

120

Atenolol release from hydrophilic matrix tablets with hydroxypropylmethylcellulose (HPMC) mixtures as gelling agent: effects of the viscosity of the HPMC mixture  

Microsoft Academic Search

The aims of this study were to assess the potential value of hydroxypropylmethylcellulose (HPMC) mixtures as gelling agents in matrix tablets for hydrosoluble drugs, and to investigate relationships between gelling agent viscosity and the kinetics of drug release from such tablets. Experiments were carried out with MethocelR K100LV (an HPMC with nominal viscosity of 100 cP) and MethocelR K100M (an

María-Jesús Vázquez; Marta Casalderrey; Roberto Duro; José-Luis Gómez-Amoza; Ramón Martínez-Pacheco; Consuelo Souto; Angel Concheiro

1996-01-01

121

Response surface optimization of sustained release metformin-hydrochloride matrix tablets: influence of some hydrophillic polymers on the release.  

PubMed

The aim of the present work was designed to develop a model-sustained release matrix tablet formulation for Metformin hydrochloride using wet granulation technique. In the present study the formulation design was employed to statistically optimize different parameters of Metformin hydrochloride tablets at different drug-to-polymer ratios employing polymers Hydroxypropyl methylcellulose of two grades K4M and K100M as two independent variables whereas the dependent variables studied were X(60), X(120), T(50), T(90), n, and b values obtained from dissolution kinetics data. The in vitro drug release studies were carried out at simulated intestinal fluids, and the release showed a non-Fickian anomalous transport mechanism. The drug release was found to reveal zero order kinetics. The granules and the tablets were tested for their normal physical, morphological, and analytical parameters and were found to be within the satisfactory levels. There were no significant drug-polymer interactions as revealed by infrared spectra. It has been found out that on an optimum increased Hydroxypropyl methylcellulose K100M concentration and decreased Hydroxypropyl methylcellulose K4M concentration the formulations were elegant in terms of their release profiles and were found to be statistically significant and generable. PMID:22988527

Roy, Amitava; Roy, Kalpana; Roy, Sarbani; Deb, Jyotirmoy; Ghosh, Amitava; Ali, Kazi Asraf

2012-01-01

122

The use of response surface methodology for the formulation and optimization of salbutamol sulfate hydrophilic matrix sustained release tablets.  

PubMed

The objective of this study was to develop a hydrophilic matrix formulation with in vitro release characteristics similar to Asthalin(®) tablets and that would sustain the release of salbutamol sulfate over a 12-h period. A central composite design was used as the framework for manufacturing formulations that may be used to understand the relationships between polymer levels and in vitro release characteristics. Tablets were manufactured using wet granulation with Surelease(®) as the granulating fluid and different levels of Methocel(®) K100M, xanthan gum, and Carbopol(®) 974P as matrix-forming materials. In vitro dissolution testing was conducted using USP Apparatus 3 and samples were analyzed using a validated reversed-phase HPLC method. The results revealed that the levels and types of polymers had a significant impact on the rate of drug release from these formulations and that it was possible to optimize the levels of matrix-forming polymers to achieve the desired release characteristics. Statistical design and response surface methodology have been successfully used to understand and optimize formulation factors and interactions that impact the in vitro release characteristics of salbutamol sulfate from a potential multisource sustained release dosage form. PMID:21428702

Chaibva, Faith A; Walker, Roderick B

2012-01-01

123

The Impact of Dose and Solubility of Additives on the Release from HPMC Matrix Tablets—Identifying Critical Conditions  

Microsoft Academic Search

Purpose  The dissolution of HPMC matrix tablets containing different amounts of highly soluble (mannitol) or poorly soluble (dicalcium\\u000a phosphate, DCP) was studied to deduce the parameters critical to release robustness.\\u000a \\u000a \\u000a \\u000a Methods  The release of HPMC and additives was studied using a modified USP II method at two paddle stirring rates, 50 and 125 rpm,\\u000a at HPMC content varying from 15% to 100%.\\u000a \\u000a \\u000a \\u000a Results  At

Farhad Tajarobi; Susanna Abrahmsén-Alami; Magnus Hansen; Anette Larsson

2009-01-01

124

Formulation and In-vitro Characterization of Sustained Release Matrix Type Ocular Timolol Maleate Mini-Tablet.  

PubMed

The purpose of this study was preparation and evaluation of sustained release matrix type ocular mini-tablets of timolol maleate, as a potential formulation for the treatment of glaucoma. Following the initial studies on timolol maleate powder, it was formulated into ocular mini-tablets. The polymers investigated in this study included cellulose derivatives (HEC, CMC, EC) and Carbopol 971P. Mannitol was used as the solubilizing agent and magnesium stearate as the lubricant. Mini-tablets were prepared by through mixing of the ingredients, followed by direct compression. All the prepared formulations were evaluated in terms of physicochemical tests, including uniformity of weight, thickness, crushing strength, friability and in-vitro drug release. Four groups of formulations were prepared. The presence of different amounts of cellulose derivatives or Carbopol 971P, alone, was studied in group A formulations. In group B formulations, the effect of adding Carbopol 971P alongside different cellulose derivatives was investigated. Group C formulations were made by including mannitol as the solubilizing agent, alongside Carbopol 971P and a cellulose derivative. In group D formulations, mini-tablets were made using Carbopol 971P, alongside two different cellulose derivative. The selected formulation (C1) contained ethyl cellulose, Carbopol 971P, mannitol and magnesium stearate, which showed almost 100% drug release over 5 h. Based on kinetic studies, this formulation was found to best fit the zero-order model of drug release. However, the Higuchi and Hixson -Crowell models also showed a good fit. Hence, overall, formulation C1 was chosen as the best formulation. PMID:24734053

Mortazavi, Seyed Alireza; Jafariazar, Zahra; Ghadjahani, Yasaman; Mahmoodi, Hoda; Mehtarpour, Farzaneh

2014-01-01

125

Formulation of Controlled-Release Baclofen Matrix Tablets II: Influence of Some Hydrophobic Excipients on the Release Rate and In Vitro Evaluation  

PubMed Central

The aim of this study was to investigate the influence of polymer level and type of some hydrophobic polymers, including hydrogenated castor oil (HCO); Eudragit RS100 (E-RS100); Eudragit L100 (E-L100), and some fillers namely mannitol [soluble filler], Dibasic calcium phosphate dihydrate (Emcompress) and anhydrous dibasic calcium phosphate [insoluble fillers] on the release rate and mechanism of baclofen from matrix tablets prepared by a hot-melt granulation process (wax tablets) and wet granulation process (E-RS100 and E-L100 tablets). Statistically significant differences were found among the drug release profile from different classes of polymeric matrices. Higher polymeric content (40%) in the matrix decreased the release rate of drug because of increased tortuosity and decreased porosity. At lower polymeric level (20%), the rate and extent of drug release was elevated. HCO was found to cause the strongest retardation of drug. On the other hand, replacement of Emcompress or anhydrous dibasic calcium phosphate for mannitol significantly retarded the release rate of baclofen, except for E-L100 (pH-dependent polymer). Emcompress surface alkalinity and in-situ increase in pH of the matrix microenvironment enhanced the dissolution and erosion of these matrix tablets. The release kinetics was found to be governed by the type and content of the excipients (polymer or filler). The prepared tablets showed no significant change in drug release rate when stored at ambient room conditions for 6 months.

Youssef Abdalla, Ossama; Salem, Hesham

2008-01-01

126

Design and Evaluation of Ethyl Cellulose Based Matrix Tablets of Ibuprofen with pH Modulated Release Kinetics  

PubMed Central

Controlled release preparations have been reported to reduce the gastro irritant and ulcerogenic effects of non steroidal antiinflammatory drugs. In the present study, an attempt was made to develop matrix tablet-based controlled release formulations of ibuprofen, using ethyl cellulose as the rate-controlling polymer. In order to prevent initial release of the drug in the acidic environment of the stomach, cellulose acetate phthalate was incorporated in the matrix in varying amounts. It was found that with increasing the proportion of ethyl cellulose in the matrix, the drug release was extended for 14-16 h. Incorporation of cellulose acetate phthalate in ethyl cellulose matrix provided very low initial release of the drug in the first 2-3 h followed by enhanced release rate in alkaline medium owing to the high solubility of cellulose acetate phthalate at basic pH which led to creation of a porous matrix. It was concluded that combination of cellulose acetate phthalate with ethyl cellulose in the matrix base can be an effective means of developing a controlled release formulation of ibuprofen with very low initial release followed with controlled release up to 14-16 h.

Chandran, S.; Asghar, Laila F. A.; Mantha, Neelima

2008-01-01

127

Design and Evaluation of Ethyl Cellulose Based Matrix Tablets of Ibuprofen with pH Modulated Release Kinetics.  

PubMed

Controlled release preparations have been reported to reduce the gastro irritant and ulcerogenic effects of non steroidal antiinflammatory drugs. In the present study, an attempt was made to develop matrix tablet-based controlled release formulations of ibuprofen, using ethyl cellulose as the rate-controlling polymer. In order to prevent initial release of the drug in the acidic environment of the stomach, cellulose acetate phthalate was incorporated in the matrix in varying amounts. It was found that with increasing the proportion of ethyl cellulose in the matrix, the drug release was extended for 14-16 h. Incorporation of cellulose acetate phthalate in ethyl cellulose matrix provided very low initial release of the drug in the first 2-3 h followed by enhanced release rate in alkaline medium owing to the high solubility of cellulose acetate phthalate at basic pH which led to creation of a porous matrix. It was concluded that combination of cellulose acetate phthalate with ethyl cellulose in the matrix base can be an effective means of developing a controlled release formulation of ibuprofen with very low initial release followed with controlled release up to 14-16 h. PMID:21394255

Chandran, S; Asghar, Laila F A; Mantha, Neelima

2008-09-01

128

Study on sustained-release metformin hydrochloride from matrix tablet: Influence of hydrophilic polymers and in vitro evaluation.  

PubMed

The overall objective of the present work was to develop an oral sustained-release (SR) metformin tablet prepared by the direct compression method, using hydrophilic hydroxylpropylmethylcellulose (HPMC) and Guar gum polymer alone and in combination at different concentrations. Metformin hydrochloride (HCl), a biguanide, has a relatively short plasma half-life and low absolute bioavailability. All the batches were evaluated for thickness, weight variation, hardness and drug content uniformity and in vitro drug release. Mean dissolution time is used to characterize the drug release rate from a dosage form, and indicates the drug release-retarding efficiency of the polymer. The hydrophilic matrix of HPMC alone could not control the Metformin release effectively for 12 h whereas when combined with Guar gum, it could slow down the release of drug and, thus, can be successfully employed for formulating SR matrix tablets. Fitting the data to the Korsmeyer equation indicated that diffusion along with erosion could be the mechanism of drug release. Similarity factor ƒ2 values suggest that the test and reference profiles are identical. PMID:23071938

Wadher, Kamlesh J; Kakde, Rajendra B; Umekar, Milind J

2011-07-01

129

Study on sustained-release metformin hydrochloride from matrix tablet: Influence of hydrophilic polymers and in vitro evaluation  

PubMed Central

The overall objective of the present work was to develop an oral sustained-release (SR) metformin tablet prepared by the direct compression method, using hydrophilic hydroxylpropylmethylcellulose (HPMC) and Guar gum polymer alone and in combination at different concentrations. Metformin hydrochloride (HCl), a biguanide, has a relatively short plasma half-life and low absolute bioavailability. All the batches were evaluated for thickness, weight variation, hardness and drug content uniformity and in vitro drug release. Mean dissolution time is used to characterize the drug release rate from a dosage form, and indicates the drug release-retarding efficiency of the polymer. The hydrophilic matrix of HPMC alone could not control the Metformin release effectively for 12 h whereas when combined with Guar gum, it could slow down the release of drug and, thus, can be successfully employed for formulating SR matrix tablets. Fitting the data to the Korsmeyer equation indicated that diffusion along with erosion could be the mechanism of drug release. Similarity factor ƒ2 values suggest that the test and reference profiles are identical.

Wadher, Kamlesh J; Kakde, Rajendra B; Umekar, Milind J

2011-01-01

130

Development of controlled-release matrix tablet of risperidone: influence of Methocel®- and Ethocel®-based novel polymeric blend on in vitro drug release and bioavailability.  

PubMed

Controlled-release (CR) matrix tablet of 4 mg risperidone was developed using flow bound dry granulation-slugging method to improve its safety profile and compliance. Model formulations F1, F2, and F3, consisting of distinct blends of Methocel® K100 LV-CR and Ethocel® standard 7FP premium, were slugged. Each batch of granules (250-1,000 ?m), obtained by crushing the slugs, was divided into three portions after lubrication and then compressed to 9-, 12-, and 15-kg hard tablets. In vitro drug release studies were carried out in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 6.8) using a paddle dissolution apparatus run at 50 rpm. The CR test tablet, containing 30% Methocel® and 60% Ethocel® (F3) with 12-kg hardness, exhibited pH-independent zero-order release kinetics for 24 h. The drug release rate was inversely proportional to the content of Ethocel®, while the gel layer formed of Methocel® helped in maintaining the integrity of the matrix. Changes in the hardness of tablet did not affect the release kinetics. The tablets were reproducible and stable for 6 months at 40 ± 2°C/75 ± 5% relative humidity. Risperidone and its active metabolite, 9-hydroxyrisperidone, present in the pooled rabbit's serum, were analyzed with HPLC-UV at ?(max) 280 nm. The CR test tablet exhibited bioequivalence to reference conventional tablet in addition to the significantly (p < 0.05) optimized peak concentration, C(max), and extended peak time, T (max), of the active moiety. There was a good association between drug absorption in vivo and drug release in vitro (R(2) = 0.7293). The successfully developed CR test tablet may be used for better therapeutic outcomes of risperidone. PMID:21494924

Badshah, Amir; Subhan, Fazal; Rauf, Khalid; Bukhari, Nadeem Irfan; Shah, Kifayatullah; Khan, Samiullah; Ahmed, Zia; Khan, Ihsanullah

2011-06-01

131

Formulation and in vitro studies of a fixed-dose combination of a bilayer matrix tablet containing metformin HCl as sustained release and glipizide as immediate release.  

PubMed

The emerging new fixed dose combination of metformin hydrocholride (HCl) as sustained release and glipizide as immediate release were formulated as a bilayer matrix tablet using hydroxy propyl methyl cellulose (HPMC) as the matrix-forming polymer, and the tablets were evaluated via in vitro studies. Three different grades of HPMC (HPMC K 4M, HPMC K 15M, and HPMC K 100M) were used. All tablet formulations yielded quality matrix preparations with satisfactory tableting properties. In vitro release studies were carried out at a phosphate buffer of pH 6.8 with 0.75% sodium lauryl sulphate w/v using the apparatus I (basket) as described in the United States Pharmacopeia (2000). The release kinetics of metformin were evaluated using the regression coefficient analysis. There was no significant difference in drug release for different viscosity grade of HPMC with the same concentration. Tablet thus formulated provided sustained release of metformin HCl over a period of 8 hours and glipizide as immediate release. PMID:18363146

Mandal, Uttam; Pal, Tapan Kumar

2008-03-01

132

Formulation development and optimization of sustained release matrix tablet of Itopride HCl by response surface methodology and its evaluation of release kinetics  

PubMed Central

The objective of this present investigation was to develop and formulate sustained release (SR) matrix tablets of Itopride HCl, by using different polymer combinations and fillers, to optimize by Central Composite Design response surface methodology for different drug release variables and to evaluate drug release pattern of the optimized product. Sustained release matrix tablets of various combinations were prepared with cellulose-based polymers: hydroxy propyl methyl cellulose (HPMC) and polyvinyl pyrolidine (pvp) and lactose as fillers. Study of pre-compression and post-compression parameters facilitated the screening of a formulation with best characteristics that underwent here optimization study by response surface methodology (Central Composite Design). The optimized tablet was further subjected to scanning electron microscopy to reveal its release pattern. The in vitro study revealed that combining of HPMC K100M (24.65 MG) with pvp(20 mg)and use of LACTOSE as filler sustained the action more than 12 h. The developed sustained release matrix tablet of improved efficacy can perform therapeutically better than a conventional tablet.

Bose, Anirbandeep; Wong, Tin Wui; Singh, Navjot

2012-01-01

133

Quantifying the release of lactose from polymer matrix tablets with an amperometric biosensor utilizing cellobiose dehydrogenase.  

PubMed

The release of lactose (hydrophilic) from polymer tablets made with hydrophobically modified poly(acrylic acid) (HMPAA) have been studied and compared to the release of ibuprofen, a hydrophobic active substance. Lactose is one of the most used excipients for tablets, but lactose release has not been widely studied. One reason could be a lack of good analytical tools. A novel biosensor with cellobiose dehydrogenase (CDH) was used to detect the lactose release, which has a polydiallyldimethylammonium chloride (PDADMAC) layer that increases the response. A sample treatment using polyethylenimine (PEI) was developed to eliminate possible denaturants. The developed methodology provided a good approach to detect and quantify the released lactose. The release was studied with or without the presence of a model amphiphilic substance, sodium dodecyl sulphate (SDS), in the release medium. Ibuprofen showed very different release rates in the different media, which was attributed to hydrophobic interactions between the drug, the HMPAA and the SDS in the release medium. The release of hydrophilic lactose, which did not associate to any of the other components, was rapid and showed only minor differences. The new methodology provides a useful tool to further evaluate tablet formulations by a relatively simple set of experiments. PMID:24726632

Knöös, Patrik; Schulz, Christopher; Piculell, Lennart; Ludwig, Roland; Gorton, Lo; Wahlgren, Marie

2014-07-01

134

Gum Ghatti--a pharmaceutical excipient: development, evaluation and optimization of sustained release mucoadhesive matrix tablets of domperidone.  

PubMed

The objective of this study was to extend the GI residence time of the dosage form and to control the release of domperidone using directly compressible sustained release mucoadhesive matrix (SRMM) tablets. A 2-factor centre composite design (CCD) was employed to study the influence of independent variables like gum ghatti (GG) (X1) and hydroxylpropylmethyl cellulose K 15M (HPMC K 15M) (X2) on dependent variable like mucoadhesive strength, tensile strength, release exponent (n), t50 (time for 50% drug release), rel(10 h) (release after 10 h) and rel(18 h) (release after 18 h). Tablets were prepared by direct compression technology and evaluated for tablet parametric test (drug assay, diameter, thickness, hardness and tensile strength), mucoadhesive strength (using texture analyzer) and in vitro drug release studies. The tensile strength and mucoadhesive strength were found to be increased from 0.665 +/- 0.1 to 1.591 +/- 0.1 MN/cm2 (Z1 to Z9) and 10.789 +/- 0.985 to 50.924 +/- 1.150 N (Z1 to Z9), respectively. The release kinetics follows first order and Hixson Crowell equation indicating drug release following combination of diffusion and erosion. The n varies between 0.834 and 1.273, indicating release mechanism shifts from non fickian (anomalous release) to super case II, which depict that drug follows multiple drug release mechanism. The t50 time was found to increase from 5 +/- 0.12 to 11.4 +/- 0.14 h (Z1 to Z9) and release after 10 and 18 h decreases with increasing concentration of both polymers concluding with release controlling potential of polymers. The accelerated stability studies were performed on optimized formulation as per ICH guideline and the result showed that there was no significant change in tensile strength, mucoadhesive strength and drug assay. PMID:22876617

Gurpreetarora; Malik, Karan; Rana, Vikas; Singh, Inderbir

2012-01-01

135

Formulation study and evaluation of matrix and three-layer tablet sustained drug delivery systems based on Carbopols with isosorbite mononitrate.  

PubMed

The purpose of this research was to develop and evaluate different preparations of sustained delivery systems, using Carbopols as carriers, in the form of matrices and three-layer tablets with isosorbite mononitrate. Matrix tablets were prepared by direct compression whereas three-layer tablets were prepared by compressing polymer barrier layers on both sides of the core containing the drug. The findings of the study indicated that all systems demonstrated sustained release. The properties of the polymer used and the structure of each formulation appear to considerably affect drug release and its release rate. The three-layer formulations exhibit lower drug release compared to the matrices. This was due to the fact that the barrier-layers hindered the penetration of liquid into the core and modified drug dissolution and release. The geometrical characteristics/structure of the tablets as well as the weight/thickness of the barriers-layers considerably influence the rate of drug release and the release mechanisms. Kinetic analysis of the data indicated that drug release from matrices was mainly attributed to Fickian diffusion while three-layer tablets exhibited either anomalous diffusion or erosion/relaxation mechanisms. The advantage of Carbopol formulations is that a range of release profiles can easily be obtained through variations in tablet structure and thus Carbopols are appropriate carriers of oral sustained drug delivery systems for soluble drugs such as the isosorbite mononitrate. PMID:18686040

Efentakis, M; Peponaki, C

2008-01-01

136

Formulation Study and Evaluation of Matrix and Three-layer Tablet Sustained Drug Delivery Systems Based on Carbopols with Isosorbite Mononitrate  

PubMed Central

The purpose of this research was to develop and evaluate different preparations of sustained delivery systems, using Carbopols as carriers, in the form of matrices and three-layer tablets with isosorbite mononitrate. Matrix tablets were prepared by direct compression whereas three-layer tablets were prepared by compressing polymer barrier layers on both sides of the core containing the drug. The findings of the study indicated that all systems demonstrated sustained release. The properties of the polymer used and the structure of each formulation appear to considerably affect drug release and its release rate. The three-layer formulations exhibit lower drug release compared to the matrices. This was due to the fact that the barrier-layers hindered the penetration of liquid into the core and modified drug dissolution and release. The geometrical characteristics/structure of the tablets as well as the weight/thickness of the barriers-layers considerably influence the rate of drug release and the release mechanisms. Kinetic analysis of the data indicated that drug release from matrices was mainly attributed to Fickian diffusion while three-layer tablets exhibited either anomalous diffusion or erosion/relaxation mechanisms. The advantage of Carbopol formulations is that a range of release profiles can easily be obtained through variations in tablet structure and thus Carbopols are appropriate carriers of oral sustained drug delivery systems for soluble drugs such as the isosorbite mononitrate.

Peponaki, C.

2008-01-01

137

Formulation development and evaluation of Diltiazem HCl sustained release matrix tablets using HPMC K4M and K100M.  

PubMed

The aim of this study was to develop a sustained release hydrophilic matrix tablet of Diltiazem HCl and evaluates the effect of formulation variables (e.g. lubricant, binder, polymer content and viscosity grades of HPMC) on drug release. Twelve different formulations (F1-F12) were prepared by direct compression. The results of the physical parameters and assay were found to be within the acceptable range. Rate of drug release was found to be slow as the fraction of the polymer was increased from 20-50%. The drug release rate from tablets containing K4M was effectively controlled by increasing the talc concentration, whereas the burst effect was reduced by increasing binder content. The drug release was higher with K4M as compare to K100M. Model-dependent and independent methods were used for data analysis and the best results were observed for K4M in Higuchi (R(2)=0.9903-0.9962) and K100M in Baker and Lonsdale (R(2)=0.9779-0.9941). The release mechanism of all formulations was non-Fickian. F7 (50% K4M, 2% talc, 10% Avicel PH101) and F11 (40% K100M) were very close to targeted release profile. F12 (50% K100M) exhibited highest degree of swelling and lowest erosion. The f1 and f2 test were performed taking F11 as a reference formulation. PMID:23811439

Qazi, Faaiza; Shoaib, Muhammad Harris; Yousuf, Rabia Ismail; Qazi, Tanveer Mustafa; Mehmood, Zafar Alam; Hasan, S M Farid

2013-07-01

138

The influence of HPMC viscosity as FRC parameter on the release of low soluble drug from hydrophylic matrix tablets.  

PubMed

The importance of functionality-related characteristics (FRC) of hydroxypropyl methylcellulose (HPMC) described in the pharmacopeia monograph can be evaluated only for selected formulation or technological process. The aim of our work was to investigate the influence of apparent viscosity as one of the FRC for two batches of the same HPMC grade on the release properties of diclofenac sodium from HPMC matrix tablets. Our results show that two batches of HPMC differ in viscosity significantly and as a consequence, the significant differences were observed in the release profiles as well. HPMC-B sample has higher viscosity and therefore higher average molecular weight, thus the erosion and drug release were slower compared to HPMC-A sample with lower apparent viscosity. It can be concluded that batch-to-batch viscosity variation of the same HPMC grade can lead to the different release profiles; therefore the specification limits of some FRC should be postulated during the development of each individual formulation. However, the viscosity interval as FRC can not be generalized, because it is different for different tablet compositions. PMID:21916601

Novak, S Devjak; Kuhelj, V; Vre?er, F; Baumgartner, S

2013-01-01

139

Investigation of the influence of mean HPMC particle size and number of polymer particles on the release of aspirin from swellable hydrophilic matrix tablets  

Microsoft Academic Search

The effects of hydroxypropyl methylcellulose (HPMC) of different particle size ranges, size distributions and concentrations on the release behaviour of aspirin from a swellable matrix tablet system were studied. A mean HPMC (Methocel K15M Premium) particle size of 113 ?m was identified as a critical threshold in this study. Drug release rate increased markedly when polymer particle size was increased

Paul Wan Sia Heng; Lai Wah Chan; Michael G Easterbrook; Xiaoman Li

2001-01-01

140

Sustained release of acetaminophen from heterogeneous matrix tablets: influence of polymer ratio, polymer loading, and co-active on drug release.  

PubMed

The aim of this research was to investigate the effect of pseudoephedrine (PE), polymer ratio, and polymer loading on the release of acetaminophen (APAP) from hydroxypropyl methyl cellulose (HPMC)/polyvinylpyrrolidone (PVP) matrices. Granules formulated with APAP or both APAP and PE, and various blends of HPMC and PVP were compressed into tablets at varying compression forces ranging from 2000 to 6000 Ib. In vitro drug release from the matrix tablets was determined and the results correlated with those of tablet water uptake and erosion studies. Drug release from the formulations containing both APAP and PE was slower than those containing only APAP (P < 0.05, F = 3.10). Drug release from tablets formulated with APAP only showed an initial burst at pH 1.16 or 7.45, and at high total polymer loading (> or = 9.6%). Formulations containing both APAP and PE showed slower drug release at pH 1.16 than at pH 7.45. At pH 1.16, a decline in the percentage of APAP released occurred after 18 hours. This was due to the hydrolysis of APAP to p-aminophenol. The drug dissolution data showed good fit to the Korsmeyer and Peppas model, and the values of the release exponents ranged from 0.20 to 0.62, indicating a complex drug release pattern. Tablet erosion studies indicated that the amount of APAP released was linearly related to the percentage of tablet weight loss. The kinetics of tablet water uptake was consistent with a diffusion and stress relaxation controlled mechanism. Overall, the results of this study indicated that PE, as a co-active in the formulation, modified the matrix, and hence retarded APAP release. PMID:9552442

Ebube, N K; Hikal, A H; Wyandt, C M; Beer, D C; Miller, L G; Jones, A B

1997-05-01

141

Evaluation of a matrix tablet prepared with polyacrylamide-g-sodium alginate co-polymers and their partially hydrolyzed co-polymers for sustained release of diltiazem hydrochloride.  

PubMed

Diltiazem hydrochloride (DTZ) matrix tablets were prepared using polyacrylamide-grafted sodium alginate (PAam-g-SA) co-polymers having different percentages of grafting and their partially hydrolyzed products with a view to achieve sustained release of the highly water-soluble drug. PAam-g-SA co-polymers having different percentages of grafting were synthesized by free radical polymerization using acrylamide (Aam) as monomer and ammonium persulphate (APS) as initiator, and the resulting co-polymers were subjected to alkaline hydrolysis to produce their corresponding partially hydrolyzed co-polymers. Matrix tablets of DTZ were prepared by wet granulation using either PAam-g-SA co-polymers or partially hydrolyzed PAam-g-SA co-polymers. The effect of percentage grafting, drug load and calcium gluconate (CG), used as excipient, was studied in simulated gastrointestinal fluid. While the tablets prepared using the co-polymer having higher percentages of grafting provided faster drug release (100% in 5.5 h), the tablets prepared with the corresponding hydrolyzed co-polymer released the drug slowly (71% in 12 h). This behaviour in release appeared to be controlled by the relative magnitude of the viscosity and the swelling capacity of the copolymers. Moreover, increase in drug load tended to decrease the drug release from all types of tablets and increase in the amount of CG increased the drug release. FT-IR and DSC studies revealed the absence of any interaction between the drug and the co-polymers. The matrix tablet made of partially hydrolyzed graft co-polymer having the highest percentage of grafting provided the most sustained release of the drug. PMID:20557689

Mandal, Sanchita; Ray, Rajat; Basu, Sanat K; Sa, Biswanath

2010-01-01

142

The effect of polymer properties on direct compression and drug release from water-insoluble controlled release matrix tablets.  

PubMed

The objective of this study was to identify and evaluate key polymer properties affecting direct compression and drug release from water-insoluble matrices. Commonly used polymers, such as Kollidon(®) SR, Eudragit(®) RS and ethyl cellulose, were characterized, formulated into tablets and compared with regard to their properties in dry and wet state. A similar site percolation threshold of 65% v/v was found for all polymers in dry state. Key parameters influencing polymer compactibility were the surface properties and the glass transition temperature (Tg), affecting polymer elasticity and particle size-dependent binding. The important properties observed in dry state also governed matrix characteristics and therefore drug release in wet state. A low Tg (Kollidon(®) SRmatrix integrity (Eudragit(®) RSmatrix systems. PMID:24746409

Grund, Julia; Koerber, Martin; Walther, Mathias; Bodmeier, Roland

2014-07-20

143

Hardware Acceleration for Finite-Element Electromagnetics: Efficient Sparse Matrix Floating-Point Computations With FPGAs  

Microsoft Academic Search

Custom hardware acceleration of electromagnetics computation leverages favorable industry trends, which indicate reconfigurable hardware devices such as field-programmable gate arrays (FPGAs) may soon outperform general-purpose CPUs. We present a new striping method for efficient sparse matrix-vector multiplication implemented in a deeply pipelined FPGA design. The effectiveness of the new method is illustrated for a representative set of finite-element matrices computed

Yousef El-Kurdi; Dennis Giannacopoulos; Warren J. Gross

2007-01-01

144

Optimization of acyclovir oral tablets based on gastroretention technology: factorial design analysis and physicochemical characterization studies.  

PubMed

The purpose of this research was to prepare a floating drug delivery system of acyclovir. Floating matrix tablets of acyclovir were developed to prolong gastric residence time and increase its bioavailability. The tablets were prepared by direct compression technique, using polymers such as hydroxypropylmethylcellulose 4000, Compritol 888. Sodium bicarbonate was used as a gas-generating agent. A 3² factorial design using the Design Expert Software (version 7.1.6) was applied to optimize the drug release profile systematically. The amounts of hydroxypropylmethylcellulose 4000 (X?) and Compritol 888 (X?) were selected as independent variables and the percentage drug released in 1 (Q?), 6 (Q?), and 12 (Q??) h as dependent variables. The results of factorial design indicated that a high level of both hydroxypropylmethylcellulose 4000 (X?) and Compritol 888 (X?) favors the preparation of floating controlled-release of acyclovir tablets. Also, a good correlation was observed between predicted and actual values of the dependent variables chosen for the study. By fitting the data into zero-order, first-order, and Higuchi models, we concluded that the release followed Higuchi diffusion kinetics. Storage of the prepared formulations at 40°C/75% relative humidity for 3 months showed no significant change in drug release profiles and buoyancy of the floating tablets. We can conclude that a combination of hydroxypropylmethylcellulose 4000, Compritol 888, and sodium bicarbonate can be used to increase the gastric residence time of the dosage form up to 12?h. These floating tablets seem to be a promising gastroretentive drug delivery system. PMID:21401342

El Gamal, Safaa S; Naggar, Viviane F; Allam, Ahmed N

2011-07-01

145

Evaluation of guar gum in the preparation of sustained-release matrix tablets.  

PubMed

Polymeric hydrophilic matrices are widely used for controlled-release preparations. The process of drug release is controlled by matrix swelling or polymer dissolution. It has been shown that the swelling of guar gum is affected by concentration of drug and viscosity grade of the polymer. This study examines the mechanism of behavior of guar gum in a polymer-drug matrix. The swelling action of guar gum, in turn, is controlled by the rate of water uptake into the matrices. An inverse relationship exists between the drug concentration in the gel and matrix swelling. This implies that guar gum swelling is one of the factors affecting drug release. The swelling behavior of guar gum is therefore useful in predicting drug release. PMID:9876566

Khullar, P; Khar, R K; Agarwal, S P

1998-11-01

146

Ca 2+ ion cross-linked interpenetrating network matrix tablets of polyacrylamide-grafted-sodium alginate and sodium alginate for sustained release of diltiazem hydrochloride  

Microsoft Academic Search

Interpenetrating network (IPN) matrix tablets of diltiazem-HCl (DTZ) was prepared by wet granulation method using polyacrylamide-grafted-sodium alginate (PAam-g-SAL) co-polymer and sodium alginate (SAL) for sustained release of the drug. Formulation of IPN structure was examined using FTIR spectroscopy, and compatibility of the drug with the polymers was evaluated through FTIR, DSC, and XRD analyses. The effect of co-polymer\\/SAL ratios, drug

Sanchita Mandal; Sanat Kumar Basu; Biswanath Sa

2010-01-01

147

Evaluation of a Matrix Tablet Prepared with Polyacrylamide-g-Sodium Alginate Co-polymers and Their Partially Hydrolyzed Co-polymers for Sustained Release of Diltiazem Hydrochloride  

Microsoft Academic Search

Diltiazem hydrochloride (DTZ) matrix tablets were prepared using polyacrylamide-grafted sodium alginate (PAam-g-SA) co-polymers having different percentages of grafting and their partially hydrolyzed products with a view to achieve sustained release of the highly water-soluble drug. PAam-g-SA co-polymers having different percentages of grafting were synthesized by free radical polymerization using acrylamide (Aam) as monomer and ammonium persulphate (APS) as initiator, and

Sanchita Mandal; Rajat Ray; Sanat K. Basu; Biswanath Sa

2010-01-01

148

[Study on application of bioassay method in drug-release evaluation in vitro of Salvia miltiorrhiza hydrophilic gel matrix tablets].  

PubMed

To investigate the feasible application of the bioassay method in the evaluation of traditional Chinese medicine sustained-release preparations, develop a rapid drug-release evaluation method in vitro for multi-component preparations, and replace the biological activity determination method characterizing the overall behavior with the existing drug-release evaluation method for single component, in order to give better instruction for sustained-release preparations. HPLC was adopted to determine dissolution media, drug releasing rates, and accumulative releasing of active ingredients (salvianolic acid B, protocatechuic aldehyde and rosmarinic acid) of Salvia Miltiorrhiza hydrophilic gel matrix tablets. The ultraviolet spectroscopy was adopted to determine the antioxidant activity of release media, and evaluate the correlation between the drug-time curve of various drug components and the drug-time curve of the total antioxidant activity. The correlation coefficient between the drug-release curve of various components and the drug-time curve of the total antioxidant activity was higher than the critical value r 0.898 (P < 0.001). This indicated that the drug-release curve of the three phenolic acids and the drug-time curve of the total antioxidant activity had a good correlation in different conditions, such as dissolution media, release rates and component ratios. The bioassay method for determination was feasible, simple and convenient for preparation quality evaluation and prescription design in the place of in vitro dissolution. PMID:24558869

Li, Dong-Ying; Liu, Xiao-Qian; Feng, Wei-Hong; Wang, Zhi-Min; Yi, Hong; Meng, Qing-Ju

2013-11-01

149

Simulation of gastric lipolysis and prediction of felodipine release from a matrix tablet in the fed stomach  

Microsoft Academic Search

The importance of intragastric lipolysis to felodipine release from a hydrophilic, extended release tablet in the fed stomach was assessed in USP II apparatus with the tablet fixed on a steel wire above the paddle. The release medium, homogenized long-life milk, was gradually digested with shots of acidic solutions of pepsin over the course of the experiment in absence and

A. Diakidou; M. Vertzoni; B. Abrahamsson; J. Dressman; C. Reppas

2009-01-01

150

Preparation and Characterization of Nicotine–Magnesium Aluminum Silicate Complex-Loaded Sodium Alginate Matrix Tablets for Buccal Delivery  

Microsoft Academic Search

Nicotine (NCT) buccal tablets consisting of sodium alginate (SA) and nicotine–magnesium aluminum silicate (NCT–MAS) complexes\\u000a acting as drug carriers were prepared using the direct compression method. The effects of the preparation pH levels of the\\u000a NCT–MAS complexes and the complex\\/SA ratios on NCT release, permeation across mucosa, and mucoadhesive properties of the tablets\\u000a were investigated. The NCT–MAS complex-loaded SA tablets

Sopaphan Kanjanabat; Thaned Pongjanyakul

2011-01-01

151

Release behaviour of propranolol HCl from hydrophilic matrix tablets containing psyllium powder in combination with hydrophilic polymers.  

PubMed

The objective of this study was to investigate the release behaviour of propranolol hydrochloride from psyllium matrices in the presence hydrophilic polymers. The dissolution test was carried out at pH 1.2 and pH 6.8. Binary mixtures of psyllium and hydroxypropyl methylcellulose (HPMC) used showed that an increase in the percentage of HPMC in the binary mixtures caused a significant decrease in the release rate of propranolol. Psyllium-alginate matrices produced lower drug release as compared to when the alginate was the matrix former alone. When sodium carboxy methyl cellulose (NaCMC) was incorporated into the psyllium, the results showed that matrices containing the ratio of psyllium-NaCMC in the 1:1 ratio are able to slow down the drug release significantly as compared to matrices made from only psyllium or NaCMC as retardant agent suggesting that there could be a synergistic effect between psyllium and NaCMC. The double-layered tablets showed that the psyllium and HPMC in the outer shell of an inner formulation of psyllium alone had the greatest effect of protecting the inner core and thus producing the lowest drug release (DE?=?38%, MDT?=?93 min). A significant decrease in the value of n in Q?=?kt(n) from 0.70 to 0.51 as the psyllium content was increased from 50 to 150 mg suggests that the presence of psyllium in HPMC matrices affected the release mechanism. Psyllium powder had the ability in the combination with other hydrophilic polymers to produce controlled release profiles. Care and consideration should as such be taken when formulating hydrophilic matrices in different combinations. PMID:21918920

Siahi-Shadbad, Mohammad R; Asare-Addo, Kofi; Azizian, Kakali; Hassanzadeh, Davoud; Nokhodchi, Ali

2011-12-01

152

Simulation of gastric lipolysis and prediction of felodipine release from a matrix tablet in the fed stomach.  

PubMed

The importance of intragastric lipolysis to felodipine release from a hydrophilic, extended release tablet in the fed stomach was assessed in USP II apparatus with the tablet fixed on a steel wire above the paddle. The release medium, homogenized long-life milk, was gradually digested with shots of acidic solutions of pepsin over the course of the experiment in absence and in presence of biorelevant concentrations of a lipase that was similar to human gastric lipase. Percentage tablet erosion at specific times in the same media was measured in separate experiments. The data were compared to published data for intragastric release in fed healthy adults. In all cases, felodipine release occurred under sink conditions. Lipase facilitated felodipine release from the eroded polymer, bringing the release profile closer to the in vivo data. Likewise, the relationship between tablet erosion and amount of released felodipine reflected the in vivo data only when lipase was added to the medium. It was concluded that modelling intragastric lipolysis is necessary in order to simulate felodipine release from the extended release tablets in the fed stomach. PMID:19429420

Diakidou, A; Vertzoni, M; Abrahamsson, B; Dressman, J; Reppas, C

2009-05-12

153

Eudragit(®) RS PO/RL PO as rate-controlling matrix-formers via roller compaction: Influence of formulation and process variables on functional attributes of granules and tablets.  

PubMed

The influence of plasticizer level, roll pressure and sintering temperature was investigated on the granule properties, tablet breaking force and theophylline release from tablets. Nine formulations using theophylline as a model drug, Eudragit(®) RL PO, Eudragit(®) RS PO, or both as a matrix former and triethyl citrate (TEC) as a plasticizer were prepared. The formulations were roller compacted and the granules obtained were evaluated for particle size distribution and flowability. These granules were compacted into tablets at a compression force of 7?kN. The tablets were thermally treated at different temperatures (50 and 75°C) for 5?h and were evaluated for breaking force and dissolution. Increase in roll pressure and TEC levels resulted in a progressive increase in the mean particle size of the granules. The flowability of the granules also improved with increasing roll pressures and TEC levels. Tablet breaking force increased with an increase in TEC levels and sintering temperatures. But these effects were significant only at the highest level of plasticizer and sintering temperature respectively. For the tablets containing Eudragit(®) RS PO, theophylline release decreased proportionately with increase in TEC levels and sintering temperatures. Tablets containing either Eudragit(®) RL PO or a mixture of RS PO and RL PO failed to impart an extended-release property to the tablets at the studied variables i.e. roll pressure, TEC levels and sintering temperature. It was clearly demonstrated that with suitable optimization of these parameters, the release-rate of a water soluble drug from the matrix tablets prepared via roller compaction can be finely controlled. PMID:22257339

Dave, Vivek S; Fahmy, Raafat M; Bensley, Dennis; Hoag, Stephen W

2012-10-01

154

The Effects of Lactose, Microcrystalline Cellulose and Dicalcium Phosphate on Swelling and Erosion of Compressed HPMC Matrix Tablets: Texture Analyzer  

PubMed Central

This paper reviews the use of texture analysis in studying the performance of hydrophilic matrices of highly soluble drugs and different types of excipients (i.e. water-soluble, water-insoluble and swellable, and water insoluble and non-swellable). Tablets were prepared by direct compression, and their swelling and erosion in presence of these different excipients were assessed with the help of volumetric, gravimetric, morphological, and rheological studies. Dissolution test was performed using USP 26 apparatus 2 modified by insertion of a sieve to prevent sticking of the tablets to the bottom of the vessel and allow them to swell 3-dimensionally. Loading 15% of the highly soluble drug in formulations containing 65% lactose showed the most pronounced swelling and erosion and the best sustained drug release, compared to matrices containing microcrystalline cellulose and dicalcium phosphate. The correlation between front movement, mass erosion and solute transport in relation to excipient type on progression of probe displacement and total work was examined throughout texture analysis studies. The formulation containing the soluble excipient lactose showed better swelling and erosion properties compared to formulations containing the swellable and insoluble excipients. In conclusion, it could be said that based on the distinct conventional dosage forms insertion of particular excipients in hydrophilic controlled release tablets containing water soluble drug, the finger print information of drug release profile could be obtained. To study the release profile from hydroxy propyl methyl cellulose K 15M matrices with different types of excpients, diltiazem hydrochloride was used as a model soluble drug.

Namdeo Tukaram, Bendgude; Vidaya Rajagopalan, Iyer; Sushi Ikumar Shartchandra, Poddar

2010-01-01

155

Study the effect of formulation variables on drug release from hydrophilic matrix tablets of milnacipran and prediction of in-vivo plasma profile.  

PubMed

The objective of this study was to design oral controlled release (CR) matrix tablets of Milnacipran using hydroxypropyl methylcellulose (HPMC) as the retardant polymer and to study the effect of various formulation factors such as polymer proportion, polymer viscosity, compression force and also the pH of dissolution medium on the in-vitro release of drug. Two viscosity grade of HPMC (15?K and 100?K) were used in the proportion of 50, 100, 150 and 200?mg per CR tablet. In-vitro release rate was characterized using various model dependent approaches and model independent dissolution parameters [T50% and T80% dissolution time, mean dissolution time (MDT), mean residence time (MRT), dissolution efficiency (DE)]. The statistical analysis was performed on all the model independent approaches using student t test and ANOVA. Results were found that as polymer concentration (50?mg to 200?mg) and viscosity (15?K to 100?K) increases, the MDT, MRT, T50% and T80% extended significantly. Drug release rate was found to be significantly different at different hardness. In-vivo human plasma concentration--time profile was predicted from in-vitro release data using convolution method. Predicted human pharmacokinetic parameters shows that the design CR formulation has capability to sustained the plasma drug level of milnacipran. PMID:23931031

Singhvi, Gautam; Shah, Abhishek; Yadav, Nilesh; Saha, Ranendra N

2014-09-01

156

Design and optimization of floating drug delivery system of acyclovir.  

PubMed

The purpose of the present work was to design and optimize floating drug delivery systems of acyclovir using psyllium husk and hydroxypropylmethylcellulose K4M as the polymers and sodium bicarbonate as a gas generating agent. The tablets were prepared by wet granulation method. A 3(2) full factorial design was used for optimization of drug release profile. The amount of psyllium husk (X1) and hydroxypropylmethylcellulose K4M (X2) were selected as independent variables. The times required for 50% (t(50%)) and 70% (t(70%)) drug dissolution were selected as dependent variables. All the designed nine batches of formulations were evaluated for hardness, friability, weight variation, drug content uniformity, swelling index, in vitro buoyancy, and in vitro drug release profile. All formulations had floating lag time below 3 min and constantly floated on dissolution medium for more than 24 h. Validity of the developed polynomial equation was verified by designing two check point formulations (C1 and C2). The closeness of predicted and observed values for t(50%) and t(70%) indicates validity of derived equations for the dependent variables. These studies indicated that the proper balance between psyllium husk and hydroxypropylmethylcellulose K4M can produce a drug dissolution profile similar to the predicted dissolution profile. The optimized formulations followed Higuchi's kinetics while the drug release mechanism was found to be anomalous type, controlled by diffusion through the swollen matrix. PMID:21694992

Kharia, A A; Hiremath, S N; Singhai, A K; Omray, L K; Jain, S K

2010-09-01

157

Design and Optimization of Floating Drug Delivery System of Acyclovir  

PubMed Central

The purpose of the present work was to design and optimize floating drug delivery systems of acyclovir using psyllium husk and hydroxypropylmethylcellulose K4M as the polymers and sodium bicarbonate as a gas generating agent. The tablets were prepared by wet granulation method. A 32 full factorial design was used for optimization of drug release profile. The amount of psyllium husk (X1) and hydroxypropylmethylcellulose K4M (X2) were selected as independent variables. The times required for 50% (t50%) and 70% (t70%) drug dissolution were selected as dependent variables. All the designed nine batches of formulations were evaluated for hardness, friability, weight variation, drug content uniformity, swelling index, in vitro buoyancy, and in vitro drug release profile. All formulations had floating lag time below 3 min and constantly floated on dissolution medium for more than 24 h. Validity of the developed polynomial equation was verified by designing two check point formulations (C1 and C2). The closeness of predicted and observed values for t50% and t70% indicates validity of derived equations for the dependent variables. These studies indicated that the proper balance between psyllium husk and hydroxypropylmethylcellulose K4M can produce a drug dissolution profile similar to the predicted dissolution profile. The optimized formulations followed Higuchi's kinetics while the drug release mechanism was found to be anomalous type, controlled by diffusion through the swollen matrix.

Kharia, A. A.; Hiremath, S. N.; Singhai, A. K.; Omray, L. K.; Jain, S. K.

2010-01-01

158

Development and evaluation of regioselective bilayer floating t ablets of Atenolol and Lovastatin for biphasic release profile  

Microsoft Academic Search

This study was performed to design bilayer regioselective floating tablets of atenolol and lovastatin to give immediate release of lovastatin and sustained release of atenolol. Bilayer floating tablets comprised two layers, i.e immediate release and controlled release layers. The immediate release layer comprised sodium starch glycollate as a super disintegrant and the sustained release layer comprised HPMC K100M and xanthan

Ajit Kulkarni; Manish Bhatia

2009-01-01

159

Development and evaluation of regioselective bilayer floating t ablets of Atenolol and Lovastatin for biphasic release profile  

Microsoft Academic Search

This study was performed to design bilayer regioselective floating tablets of atenolol and lovastatin to give immediate release of lovastatin and sustained release of atenolol. Bilayer floating tablets comprised two layers, i.e immediate release and controlled release layers. The immediate release layer comprised sodium starch glycollate as a super disintegrant and the sustained release layer comprised HPMC K100M and xanthan

Ajit Kulkarni; Manish Bhatia

160

Effect of hydrophilic natural gums in formulation of oral-controlled release matrix tablets of propranolol hydrochloride.  

PubMed

In order to develop a controlled delivery of highly water-soluble propranolol hydrochloride (PPHCl) using hydrophilic natural gums (xanthan gum [X] and locust bean gum [LBG]) as cost-effective, nontoxic, easily available. The granules of PPHCl were prepared by wet granulation method using a different ratios drug: gum ratios of X, LBG and XLBG(X and LBG in 1:1 ratios). To increase the flowability and compressibility of the granules, and to prevent its adhesion to punch and die, magnesium stearate and talc were added to the granules in 1:2 ratios before punching. The tablet was analysed to determine hardness, friability, % assay and invitro release study was carried out. The release of PPHCl from a gelatinous swollen mass, which controls the diffusion of drug molecules through the polymeric material into aqueous medium. The XLBG matrice shows precise controlled release than the X and LBG matrice because of burst effect and fast release in case of X and LBG matrice respectively and there was no chemical interaction between drug and polymer in XLBG formulation as confirmed by FTIR studies. First pass effect of PPHCl can be avoided by these formulations. Matrices with XLBG show zero-order release via swelling, diffusion and relaxation mechanism. The XLBG matrice leads to more precise result than X and LBG alone by the utilization of synergistic interaction between two biopolymers and uniformity in the hydration layer in dissolution media. However, according to the similarity factor (f(2)) XLBG3 were the most similar formulations to Lol-SR as the reference standard. PMID:19339235

Rajesh, K S; Venkataraju, M P; Gowda, D V

2009-04-01

161

Floating Boats  

ERIC Educational Resources Information Center

The purpose of this article is to describe a simple laboratory activity in which students collect a series of measurements and then use graphical analysis to determine the nature of the relationship between an object's mass and the volume of water it displaces. In this activity, students explore the relationships between the mass of a floating

Waugh, Michael

2007-01-01

162

Floating Butterfly  

NSDL National Science Digital Library

In this activity, learners create a cool floating animal using the science of magnetism. Learners discover what happens when a piece of magnetic metal enters a magnet's field. Learners also examine magnetic poles. Note, a drill is required for this activity, and is not included in the cost of materials.

Workshop, Fresno C.

2012-01-01

163

Ice Floats  

NSDL National Science Digital Library

This is a lesson about displacement, buoyancy, and density. Learners will understand why ice floats. Includes background information, teacher notes, assessment criteria, and related resources; activities are differentiated for Pre-K-grade 2 and grades 3-5. This is lesson 4 of the unit Exploring Ice in the Solar System.

164

On floats and float tests  

NASA Technical Reports Server (NTRS)

The principal source of information on float resistance is the model test. In view of the insuperable difficulties opposing any attempt at theoretical treatment of the resistance problem, particularly at attitudes which tend toward satisfactory take-off, such as the transitory stage to planing, the towing test is and will remain the primary method for some time.

Seewald, Friedrich

1931-01-01

165

Effect of HPMC - E15 LV premium Polymer on Release Profile and Compression Characteristics of Chitosan/ Pectin Colon Targeted Mesalamine Matrix Tablets and in vitro Study on Effect of pH Impact on the Drug Release Profile.  

PubMed

The study was designed to investigate the in vitro dissolution profile and compression characteristics of colon targeted matrix tablets prepared with HPMC E15 LV in combination with pectin and Chitosan. The matrix tablets were subjected to two dissolution models in various simulated fluids such as pH 1.2, 6, 6.8, 7.2, 5.5. The fluctuations in colonic pH conditions during IBD (inflammatory bowel disease) and the nature of less fluid content in the colon may limit the expected drug release in the polysaccharide-based matrices when used alone. The Hydrophilic hydroxyl propyl methylcellulose ether premium polymer (HPMC E15 LV) of low viscosity grade was used in the formulation design, which made an excellent modification in physical and compression characteristics of the granules. The release studies indicated that the prepared matrices could control the drug release until the dosage form reaches the colon and the addition HPMC E15 LV showed the desirable changes in the dissolution profile by its hydrophilic nature since the colon is known for its less fluid content. The hydrophilic HPMC E15 LV allowed the colonic fluids to enter into the matrix and confirmed the drug release at the target site from a poorly water soluble polymer such as Chitosan and also from water soluble Pectin. The dramatic changes occurred in the drug release profile and physicochemical characteristics of the Pectin, Chitosan matrix tablets when a premium polymer HPMC E15 LV added in the formulation design in the optimized concentration. Various drug release mechanisms used for the examination of drug release characteristics. Drug release followed the combined mechanism of diffusion, erosion, swelling and polymer entanglement. In recent decade, IBD attracts many patents in novel treatment methods by using novel drug delivery systems. PMID:24597626

Newton, A M J; Lakshmanan, Prabakaran

2014-04-01

166

Preparation and in-vitro in-vivo evaluation of sustained release matrix diclofenac sodium tablets using PVP-K90 and natural gums.  

PubMed

Conventional dosage form is nowadays mostly replaced by sustained release formulation in order to increase drug efficacy and patient compliance. The sustained release properties of the PVP K90 alone and in combination with guar gum, xanthan gum and gum tragacanth were evaluated using diclofenac sodium (100 mg/tablet) as a model drug. Tablets were processed using wet granulation method and evaluated for sustained drug release properties. The drug release from the formulations was studied in relationship with Commercially available Diclofenac Sodium SR, used as a reference tablets and results were expressed as similarity (f1) and differential factor (f2). The tablets prepared using PVP K90 160 mg/tablet sustained the release of diclofenac sodium for 12 hours. Formulations where the PVP K90 was partially replaced with different gums also sustained the release of drug for 12 hours. The release of the drug from these formulations mainly followed Higuchi model and super case-II and Non-Fickian diffusion. The in-vivo drug release was studied in healthy human volunteers using non-blinded cross over, two period design using Diclofenac Sodium SR Tablets as a reference drug. The relative bioavailability of the formulation containing PVP K90 and gum tragacanth was 0.91. The studies showed that the use of the PVP K90 in combination with gum tragacanth both in-vitro and in-vivo sustained the release of the drug. PMID:21959802

Iqbal, Zafar; Khan, Raza; Nasir, Fazli; Khan, Jamshaid Ali; Rashid, Abdur; Khan, Abbas; Khan, Abad

2011-10-01

167

A Floating-Point Multiplexed DDA System  

Microsoft Academic Search

The design of a high-speed, high-accuracy floating-point digital differential analyzer (DDA) system is described. The advantages of a floating-point system are expounded. It is shown that the problem of module interconnection can be alleviated using matrix methods, and a practical implementation of a multiplexed system with a semiconductor fast data storage area is described.

Geoff Hannington; Donald G. Whitehead

1976-01-01

168

Matrix tablets: the effect of hydroxypropyl methylcellulose/anhydrous dibasic calcium phosphate ratio on the release rate of a water-soluble drug through the gastrointestinal tract I. In vitro tests.  

PubMed

Different hydroxypropyl methylcellulose (HPMC)/anhydrous dibasic calcium phosphate (ADCP) matrix tablets have been developed aiming to evaluate the influence of both components ratio in the control release of a water-soluble drug (theophylline). In order to characterise the matrix tablets, swelling, buoyancy and dissolution studies have been carried out in different aqueous media (demineralised water, progressive pH medium, simulated gastric fluid, simulated intestinal fluid and simulated colonic fluid). The HPMC/ADCP ratio has turned out to be the determinant in the matrix behaviour: the HPMC characteristic swelling behaviour was modulated, in some cases, by the ADCP characteristic acidic dissolution. When the HPMC/ADCP ratio was ?0.69, buoyancy, continuous swelling and low theophylline dissolution rate from the matrices (H1, H2 and H3) were observed in all dissolution media. Consequently, these formulations could be adequate as gastro-retentive drug delivery systems. Additionally, HPMC/ADCP ratio ?0.11 (H5 and H6) induces a pH-dependent drug release which could be applied to design control drug release enteric formulations (with a suitable enteric coating). Finally, a HPMC/ADCP ratio between 0.11 and 0.69 (H4) yield a gastrointestinal controlled drug release, due to its time-dependent buoyancy (7 h) and a total drug delivery in 17 h in simulated colonic fluid. PMID:22907778

Mamani, Pseidy L; Ruiz-Caro, Roberto; Veiga, María D

2012-12-01

169

Formulation and evaluation of fixed-dose combination of bilayer gastroretentive matrix tablet containing atorvastatin as fast-release and atenolol as sustained-release.  

PubMed

The objective of the present study was to develop bilayer tablets of atorvastatin and atenolol that are characterized by initial fast-release of atorvastatin in the stomach and comply with the release requirements of sustained-release of atenolol. An amorphous, solvent evaporation inclusion complex of atorvastatin with ? -cyclodextrin, present in 1 : 3 (drug/cyclodextrin) molar ratio, was employed in the fast-release layer to enhance the dissolution of atorvastatin. Xanthan gum and guar gum were integrated in the sustained-release layer. Bilayer tablets composed of sustained-release layer (10% w/w of xanthan gum and guar gum) and fast-release layer [1 : 3 (drug/cyclodextrin)] showed the desired release profile. The atorvastatin contained in the fast-release layer showed an initial fast-release of more than 60% of its drug content within 2 h, followed by sustained release of the atenolol for a period of 12 h. The pharmacokinetic study illustrated that the fast absorption and increased oral bioavailability of atorvastatin as well as therapeutic concentration of atenolol in blood were made available through adoption of formulation strategy of bilayer tablets. It can be concluded that the bilayer tablets of atorvastatin and atenolol can be successfully employed for the treatment of hypertension and hypercholesterolemia together through oral administration of single tablet. PMID:24527446

Dey, Sanjay; Chattopadhyay, Sankha; Mazumder, Bhaskar

2014-01-01

170

Secure tracking of tablets  

US Patent & Trademark Office Database

The present invention relates to a verification method for tracking and tracing tablets, particularly pharmaceutical tablets. It further relates to a visible secure marking or information that is a part of such tablet (10). The invention further relates to tablets suitable for such verification method, processes for manufacturing such tablets, and methods for reading the information.

2014-05-06

171

Floating Boats  

NSDL National Science Digital Library

The purpose of this article is to describe a simple laboratory activity in which students collect a series of measurements and then use graphical analysis to determine the nature of the relationship between an object's mass and the volume of water it displaces. In this activity, students explore the relationships between the mass of a floating object, the amount the object sinks in the water, and its displaced volume. The data will reveal a unique relationship between an object's metrically measured mass and volume and its buoyancy in water. This can lead to an elaboration of the density concept and provide a concrete model for systems involving other forms of balance and equilibrium.

Waugh, Michael

2007-07-01

172

Compressibility of floating pellets with verapamil hydrochloride coated with dispersion Kollicoat SR 30 D  

Microsoft Academic Search

The purpose of this study was to work out a method of compression of floating pellets with verapamil hydrochloride (VH) in a dose of 40mg. It was assumed that this form should reside in the stomach floating for several hours and gradually release the drug in a controlled way. Compression of pellets into tablets, being a modern technological process, is

Wies?aw Sawicki; Rafa? ?unio

2005-01-01

173

tablet excipients  

Microsoft Academic Search

\\u000a In addition to the active drug, medicinal products often contain a number of other substances, e.g. for improving bioavailability such as disintegrants (e.g. starch), for taste masking and lubrication to ease swallowing (e.g. coats of sugar, cellulose,\\u000a polymers in film-coated tablets), or simply substances which facilitate production such as binders (e.g. cellulose derivatives),\\u000a glidants (colloidal silica) or diluents (lactose, crystalline

Gerhard Nahler

174

Evaluation of honey locust (Gleditsia triacanthos Linn.) gum as sustaining material in tablet dosage forms.  

PubMed

In this study, honey locust gum (HLG) obtained from Gleditsia triacanthos (honey locust) beans was investigated as a hydrophilic matrix material in the tablets prepared at different concentrations (5% and 10%) by wet granulation method. Theophylline was chosen as a model drug. The matrix tablets containing hydroxyethylcellulose and hydroxypropyl methylcellulose as sustaining polymers at the same concentrations were prepared and a commercial sustained release (CSR) tablet containing 200 mg theophylline was examined for comparison of HLG performance. Physical analysis on CSR tablet, matrix tablets and their granules before compression were performed. According to the results obtained from dissolution studies in distilled water, pH 1.2 HCl buffer and pH 7.2 phosphate buffer, no significant difference was found between CSR tablet and the matrix tablet containing 10% HLG in each medium (P > 0.05) and these tablets showed zero-order kinetic model in all the mediums. PMID:15231434

Uner, Melike; Altinkurt, Turan

2004-07-01

175

Bioequivalence of Clozapine Tablets  

Microsoft Academic Search

Objective To perform a bioequivalence study of clozapine tablets between Clozaril ? tablet (Novartis), the innovator product, and Clopaze ? tablet (Pharminar, Thailand). Method The study was performed in 12 healthy male volunteers for a single 100 mg dose of clozapine tablet. Randomized cross over design was used. Blood samples were collected before and after drug administration for 24 hours

Wandee Taesotikul; Sayam Kaewvichit; Chokchai Wongsinsup; Kittipong Sanichwankul; Wanida Pumpaisalchai

2000-01-01

176

Direct analysis of 18 flavonol glycosides, aglycones and terpene trilactones in Ginkgo biloba tablets by matrix solid phase dispersion coupled with ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometry.  

PubMed

Analysis and quality control of Ginkgo biloba have been comprehensively studied. However, little attention has been devoted to the simultaneous extraction and analysis of flavonols and terpene trilactones, especially for direct quantification of flavonol glycosides. This work described a rapid strategy for one-step extraction and quantification of the components. A matrix solid phase dispersion (MSPD) method was designed for the extraction of ginkgo ingredients and compared with the heat-reflux and ultrasonic extraction methods. An ultra-high performance liquid chromatography (UHPLC)-tandem-triple-quadrupole-mass spectrometry (QQQ-MS) method was developed for detection of the 18 components, including 10 original flavonol glycosides, 3 aglycones, and 5 lactones. Subsequently, the proposed strategy was used for the analysis of 12 G. biloba tablets. Results showed that MSPD produced comparable extraction efficiency but consumed less time and required lower solvent volumes compared with conventional methods. Without hydrolysis, the concentration detected was much closer to the original in the sample. The total flavonol glycoside contents in ginkgo tablets ranged from 3.59 to 125.21?gmg(-1), and the terpene trilactone varied from 3.45 to 57.8?gmg(-1) among different manufacturers. In conclusion, the proposed MSPD and UHPLC-QQQ-MS is rapid and sensitive in providing comprehensive profile of chemical constituents especially the genuine flavonol glycosides for improved quality control of ginkgo products. PMID:24876067

Liu, Xin-Guang; Yang, Hua; Cheng, Xiao-Lan; Liu, Lei; Qin, Yong; Wang, Qi; Qi, Lian-Wen; Li, Ping

2014-08-01

177

Preparation and characterization of a gastric floating dosage form of capecitabine.  

PubMed

Gastrointestinal disturbances, such as nausea and vomiting, are considered amongst the main adverse effects associated with oral anticancer drugs due to their fast release in the gastrointestinal tract (GIT). Sustained release formulations with proper release profiles can overcome some side effects of conventional formulations. The current study was designed to prepare sustained release tablets of Capecitabine, which is approved by the Food and Drug Administration (FDA) for the treatment of advanced breast cancer, using hydroxypropyl methylcellulose (HPMC), carbomer934P, sodium alginate, and sodium bicarbonate. Tablets were prepared using the wet granulation method and characterized such that floating lag time, total floating time, hardness, friability, drug content, weight uniformity, and in vitro drug release were investigated. The sustained release tablets showed good hardness and passed the friability test. The tablets' floating lag time was determined to be 30-200 seconds, and it floated more than 24 hours and released the drug for 24 hours. Then, the stability test was done and compared with the initial samples. In conclusion, by adjusting the right ratios of the excipients including release-retarding gel-forming polymers like HPMC K4M, Na alginate, carbomer934P, and sodium bicarbonate, sustained release Capecitabine floating tablet was formulated. PMID:24288681

Taghizadeh Davoudi, Ehsan; Ibrahim Noordin, Mohamed; Kadivar, Ali; Kamalidehghan, Behnam; Farjam, Abdoreza Soleimani; Akbari Javar, Hamid

2013-01-01

178

Multispectral imaging of tablets in blister packaging.  

PubMed

This experiment tested the hypothesis that using near-infrared (IR) imaging spectrometry on tablets through blister packs permits the identification and composition of multiple individual tablets to be determined simultaneously. Aspirin was selected for this study because its breakdown mechanism is well understood. Near-IR cameras were used to collect thousands of spectra simultaneously from a field of packaged aspirin tablets. Tablets were selected by a principal component analysis selection algorithm. Graphs of the columns of the transformation matrix showed that salicylic acid and acetylsalicylic acid in the samples were modeled by the principal components. The bootstrap error-adjusted single-sample technique chemometric-imaging algorithm was used to draw probability-density contour plots that revealed tablet composition. Choice of color was used to represent constituent identity, whereas intensity represented concentration. The percentage of usable pixels in the indium antimonide (InSb) array was 99.9%. The SEP was 0.06% of the tablet mass for both water uptake and salicylic acid production. The number of tablets that a typical near-IR camera can currently analyze simultaneously was also estimated to be approximately 1300. PMID:14727884

Malik, I; Poonacha, M; Moses, J; Lodder, R A

2001-01-01

179

Terahertz technology: a boon to tablet analysis.  

PubMed

The terahertz gap has a frequency ranges from approximately 0.3 THz to approximately 10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets. PMID:20490288

Wagh, M P; Sonawane, Y H; Joshi, O U

2009-05-01

180

Development of Single Layer Acetaminophen Extended Release Tablet with Biphasic Release  

Microsoft Academic Search

Immediate release and sustained release acetaminophen (APAP) granulations can be blended together and compressed into simple monolithic matrix tablets having a similar biphasic release pattern demon- strated by commercial APAP extended release bilayer tablets. This new approach is simple, cost effective and yields robust, stable tablets.

Divya Tewari; Richard K. Lewis; Thomas Dürig; Weldon W. Harcum; Hercules Plaza

181

Floating microspheres: to prolong the gastric retention time in stomach.  

PubMed

A gastroretentive drug delivery system with prolong retention time in the stomach have great practical importance for drugs with an absorption window in the upper small intestine. Floating drug delivery system are expected to remain buoyant in the gastric content for prolong duration of time thus enhance the bioavailability of drugs. There are several gastroretentive drug delivery systems, which are floating microspheres, granules, tablets, powder, pills, laminated films and capsules. Floating microspheres are gaining special attention because of their wide applicability in the targeting of drug to stomach. Floating microspheres have several advantages, that they remain buoyant in the stomach and distributed uniformly to avoid the vagaries of gastric emptying and release the drug for prolong period of time. PMID:22023206

Bhadouriya, Priyanka; Kumar, Manish; Pathak, Kamla

2012-05-01

182

What floats a float nurse's boat?  

PubMed

Few studies have examined the personality traits of nurses, and none identified the personality traits of float pool nurses. Float pool nurses have specific personality traits that differ from unit-based nurses. Independence, Tough-Mindedness, Rule Consciousness, Social Boldness, Openness to Change, and Tension were six personality factors that were found to be statistically significantly different. As hospitals implement float pools or resource teams to meet staffing needs, gleaning insight into the specific personality traits of these individuals could assist in nurse recruitment and retention. PMID:21961124

Linzer, Pamela; Tilley, Ann Marie; Williamson, Marlene V

2011-01-01

183

Drug Release from Tablets Containing Cellulose Acetate Phthalate As an Additive or Enteric-Coating Material  

Microsoft Academic Search

A formulation containing cellulose acetate phthalate for preparing enteric-coated granules was developed with the use of granulation and microencapsulation techniques. Drug release from tablets or tabletted microcapsules was measured in a disintegration apparatus and an in vitro variable-pH release simulator of the flow type. The release mechanism for the tablets or tabletted microcapsules was determined with the Higuchi matrix model,

Shan-Yang Lin; Y. Kawashima

1987-01-01

184

Clinical evaluation of sodium flouride chewable tablets in dental caries.  

PubMed

Chewable tablets containing low dosage flouride content were prepared using two varities of celluloses and their in vitro parameters were evaluated. An eighteen month clinical trial revealed that both these formulations were effective in controlling the caries. However, ethyl cellulose is proved to be superior to methylcellulose as a controlled release matrix material in controlling caries. Thus this study recommends ethylcellulose matrix tablets containing low flouride content is an efficacious and cost effective drug device in controlling dental caries. PMID:10865398

Maddi, S S; Tandon, S; Aithal, K S

1999-01-01

185

Charge retention characteristics of silicide-induced crystallized polycrystalline silicon floating gate thin-film transistors for active matrix organic light-emitting diode.  

PubMed

In this work, non-volatile memory thin-film transistor (NVM-TFT) was fabricated by nickel silicide-induced laterally crystallized (SILC) polycrystalline silicon (poly-Si) as the active layer. The nickel seed silicide-induced crystallized (SIC) poly-Si was used as storage layer which is embedded in the gate insulator. The novel unit pixel of active matrix organic light-emitting diode (AMOLED) using NVM-TFT is proposed and investigated the electrical and optical performance. The threshold voltage shift showed 17.2 V and the high reliability of retention characteristic was demonstrated until 10 years. The retention time can modulate the recharge refresh time of the unit pixel of AMOLED up to 5000 sec. PMID:24245194

Park, Jae Hyo; Son, Se Wan; Byun, Chang Woo; Kim, Hyung Yoon; Joo, So Na; Lee, Yong Woo; Yun, Seung Jae; Joo, Seung Ki

2013-10-01

186

Float Zone Workshop  

NASA Technical Reports Server (NTRS)

A summary of the Analytical Float Zone Experiment System (AFZES) concept is presented. The types of experiments considered for such a facility are discussed. Reports from various industrial producers and users of float zone material are presented. Special emphasis is placed on state-of-the-art developments in low gravity manufacturing and their applications to space processing.

Naumann, R. J.

1980-01-01

187

Floating point error analysis  

Microsoft Academic Search

In many floating point calculations it is important to arrange the sequence of calculations such that significant digits are not deleted by intermediate rounding of the numbers. The danger that gross errors may be introduced is always present in floating point calculations, since the number of digits carried in each number is restricted in normal operation by the design of

R. C. Nickerson

1959-01-01

188

Floating islands of Turkey  

Microsoft Academic Search

Turkey abounds in both natural as well as cultural richness. Especially the natural assets located in developing regions have an important role to play in the economic life of such areas. The floating islands are one of these assets and have become an important research subject lately. Turkey is considered as a heaven of floating islands. Almost all geographical regions

Ihsan Bulut

2011-01-01

189

Femara Tablets.doc  

Cancer.gov

____________________________________________________________________________________________________ Femara® Tablets, 2.5 mg Page 1 of 7 Approval Date: 28 Oct 03 1 0 0 MATERIAL SAFETY DATA SHEET NOVARTIS PHARMACEUTICALS CORPORATION One Health Plaza

190

Algorithms for Matrix Multiplication.  

National Technical Information Service (NTIS)

Strassen's and Winograd's algorithms for matrix multiplication are investigated and compared with the normal algorithm. Floating - point error bounds are obtained, and it is shown that scaling is essential for numerical accuracy using Winograd's method. I...

R. P. Brent

1970-01-01

191

[Formulation of calcium acetate tablets].  

PubMed

The results of the testing of calcium acetate tablets, produced by direct compression and by wet granulation (Ph. Jug. IV) are presented. Tablet hardness, friability and disintegration were determined. The best properties were observed in the tablets produced with maize starch. This procedure is fast and simple, and compound tablets of calcium acetate fulfill the current requirements for this type of preparation. PMID:11521467

Obrenovic, D; Gazikalovic, E; Ognjanovic, J; Nidzovic Z, Z

2000-01-01

192

Concrete production floating platforms  

SciTech Connect

The floating production platforms operating in the North Sea are adapted from drilling semisubmersibles which allow only a limited payload capacity. Experience of concrete production platforms constructed for the North Sea has led Sea Tank Co. to propose a floating platform which offers large payload and oil storage capacities similar to those of existing fixed platforms. Sea Tank Co. and Institut Francais du Petrole joined forces in early 1976 to study the feasibility of a concrete floating production platform incorporating the structure and the production riser together. The results of this 3-yr program show that the concrete floating structure is economically attractive for permanent utilization on a production site. Furthermore, concrete has definite advantages over other materials, in its long term behavior.

Letourneur, O.; Falcimaigne, J.

1981-01-01

193

Micromechanisms with floating pivot  

DOEpatents

A new class of tilting micromechanical mechanisms have been developed. These new mechanisms use floating pivot structures to relieve some of the problems encountered in the use of solid flexible pivots.

Garcia, Ernest J. (Albuquerque, NM)

2001-03-06

194

Floating Magnet Demonstration.  

ERIC Educational Resources Information Center

A room-temperature demonstration of a floating magnet using a high-temperature superconductor is described. The setup and operation of the apparatus are described. The technical details of the effect are discussed. (CW)

Wake, Masayoshi

1990-01-01

195

Floating Squares (GCMP)  

NSDL National Science Digital Library

Floating Squares: this is a resource in the collection "General Chemistry Multimedia Problems". In this problem we will coat a piece of notecard with graphite (from pencil lead). We then will float the piece in two beakers containing water and a second solvent. General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.

196

The influence of hydroxypropyl methylcellulose (HPMC) molecular weight, concentration and effect of food on in vivo erosion behavior of HPMC matrix tablets.  

PubMed

Four different hydrophilic matrix formulations based on hydroxypropyl methylcellulose (HPMC) were investigated for erosion properties in vivo. Three formulations contained a fixed amount of HPMC (40%) with varying proportions of two HPMC grades with different molecular weights (Methocel K100LV and K4M), and a fourth formulation contained a lower amount of the HPMC of lower molecular weight (20%). The effect of food on the in vivo erosion behavior was investigated on two formulations containing different contents of the same HPMC grade. The in vivo erosion behavior and gastrointestinal transit were investigated using magnetic marker monitoring (MMM). The in vitro and in vivo erosion-time profiles show that the erosion was strongly dependent on the composition of the formulation. The formulations containing a larger proportion of high molecular weight HPMC or higher content of HPMC exhibit relatively slower erosion rate and vice versa. In vivo erosion rates were significantly higher under postprandial administration as compared to fasted state administration. No rapid disintegration of any of the formulations (i.e. formulation failure that can potentially cause dose dumping) was observed. PMID:24818771

Jain, Arun Kumar; Söderlind, Erik; Viridén, Anna; Schug, Barbara; Abrahamsson, Bertil; Knopke, Christian; Tajarobi, Farhad; Blume, Henning; Anschütz, Maria; Welinder, Anette; Richardson, Sara; Nagel, Stefan; Abrahmsén-Alami, Susanna; Weitschies, Werner

2014-08-10

197

Design and study of lamivudine oral controlled release tablets.  

PubMed

The objective of this study was to design oral controlled release matrix tablets of lamivudine using hydroxypropyl methylcellulose (HPMC) as the retardant polymer and to study the effect of various formulation factors such as polymer proportion, polymer viscosity, and compression force on the in vitro release of drug. In vitro release studies were performed using US Pharmacopeia type 1 apparatus (basket method) in 900 mL of pH 6.8 phosphate buffer at 100 rpm. The release kinetics were analyzed using the zero-order model equation, Higuchi's square-root equation, and the Ritger-Peppas empirical equation. Compatibility of the drug with various excipients was studied. In vitro release studies revealed that the release rate decreased with increase in polymer proportion and viscosity grade. Increase in compression force was found to decrease the rate of drug release. Matrix tablets containing 60% HPMC 4000 cps were found to show good initial release (26% in first hour) and extended the release up to 16 hours. Matrix tablets containing 80% HPMC 4000 cps and 60% HPMC 15,000 cps showed a first-hour release of 22% but extended the release up to 20 hours. Mathematical analysis of the release kinetics indicated that the nature of drug release from the matrix tablets was dependent on drug diffusion and polymer relaxation and therefore followed non-Fickian or anomalous release. No incompatibility was observed between the drug and excipients used in the formulation of matrix tablets. The developed controlled release matrix tablets of lamivudine, with good initial release (20%-25% in first hour) and extension of release up to 16 to 20 hours, can overcome the disadvantages of conventional tablets of lamivudine. PMID:18181522

Ravi, Punna Rao; Ganga, Sindhura; Saha, Ranendra Narayan

2007-01-01

198

Calcification prevention tablets  

NASA Technical Reports Server (NTRS)

Citric acid tablets, which slowly release citric acid when flushed with water, are under development by the Navy for calcification prevention. The citric acid dissolves calcium carbonate deposits and chelates the calcium. For use in urinals, a dispenser is not required because the tablets are non-toxic and safe to handle. The tablets are placed in the bottom of the urinal, and are consumed in several hundred flushes (the release rate can be tailored by adjusting the formulation). All of the ingredients are environmentally biodegradable. Mass production of the tablets on commercial tableting machines was demonstrated. The tablets are inexpensive (about 75 cents apiece). Incidences of clogged pipes and urinals were greatly decreased in long term shipboard tests. The corrosion rate of sewage collection pipe (90/10 Cu/Ni) in citric acid solution in the laboratory is several mils per year at conditions typically found in traps under the urinals. The only shipboard corrosion seen to date is of the yellow brass urinal tail pieces. While this is acceptable, the search for a nontoxic corrosion inhibitor is underway. The shelf life of the tablets is at least one year if stored at 50 percent relative humidity, and longer if stored in sealed plastic buckets.

Lindsay, Geoffrey A.; Hasting, Michael A.; Gustavson, Michael A.

1991-01-01

199

Mucoadhesive bilayered tablets for buccal sustained release of flurbiprofen  

Microsoft Academic Search

The aim of this work was the design of sustained-release mucoadhesive bilayered tablets, using mixtures of mucoadhesive polymers\\u000a and an inorganic matrix (hydrotalcite), for the topical administration of flurbiprofen in the oral cavity. The first layer,\\u000a responsible for the tablet retention on the mucosa, was prepared by compression of a cellulose derivative and polyacrylic\\u000a derivative blend. The second layer, responsible

Luana Perioli; Valeria Ambrogi; Stefano Giovagnoli; Maurizio Ricci; Paolo Blasi; Carlo Rossi

2007-01-01

200

Imperatorin sustained-release tablets: In Vitro and pharmacokinetic studies  

Microsoft Academic Search

We prepared and evaluated imperatorin (IMP) sustained-release tablets. IMP is an active compound in Angelica dahuricae, a\\u000a Chinese herbal medicine. We used different polymers, such as hydroxypropyl methylcellulose (HPMC K4M, K15M, and K100M), carbopol\\u000a 934P, sodium carboxymethyl cellulose (CMC-Na), and their combinations to prepare the matrix tablets and achieve the desired\\u000a sustained release profile. The in vitro release profiles of

Jingjing Pan; Wen Lu; Changhui Li; Sicen Wang; Langchong He

2010-01-01

201

Development of Press-Coated, Floating-Pulsatile Drug Delivery of Lisinopril  

PubMed Central

Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor, primarily used for the treatment of hypertension, congestive heart failure, and heart attack. It belongs to BCS class III having a half-life of 12 hrs and 25% bioavailability. The purpose of the present work was to develop a press-coated, floating-pulsatile drug delivery system. The core tablet was formulated using the super-disintegrants crosprovidone and croscarmellose sodium. A press-coated tablet (barrier layer) contained the polymer carrageenan, xanthan gum, HPMC K4M, and HPMC K15M. The buoyant layer was optimized with HPMC K100M, sodium bicarbonate, and citric acid. The tablets were evaluated for physical characteristics, floating lag time, swelling index, FTIR, DSC, and in vitro and in vivo behavior. The 5% superdisintgrant showed good results. The FTIR and DSC study predicted no chemical interactions between the drug and excipients. The formulation containing xanthan gum showed drug retaining abilities, but failed to float. The tablet containing HPMC K15M showed a high swelling index. The lag time for the tablet coated with 200 mg carrageenan was 3±0.1 hrs with 99.99±1.5% drug release; with 140 mg HPMC K4M, the lag time was 3±0.1 hrs with 99.71±1.2% drug release; and with 120 mg HPMC K15M, the lag time was 3±0.2 hrs with 99.98±1.7% drug release. The release mechanism of the tablet followed the Korsmeyer-Peppas equation and a first-order release pattern. Floating and lag time behavior have shown good in vitro and in vivo correlations.

Jagdale, Swati C.; Suryawanshi, Vishnu M.; Pandya, Sudhir V.; Kuchekar, Bhanudas S.; Chabukswar, Aniruddha R.

2014-01-01

202

Development of press-coated, floating-pulsatile drug delivery of lisinopril.  

PubMed

Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor, primarily used for the treatment of hypertension, congestive heart failure, and heart attack. It belongs to BCS class III having a half-life of 12 hrs and 25% bioavailability. The purpose of the present work was to develop a press-coated, floating-pulsatile drug delivery system. The core tablet was formulated using the super-disintegrants crosprovidone and croscarmellose sodium. A press-coated tablet (barrier layer) contained the polymer carrageenan, xanthan gum, HPMC K4M, and HPMC K15M. The buoyant layer was optimized with HPMC K100M, sodium bicarbonate, and citric acid. The tablets were evaluated for physical characteristics, floating lag time, swelling index, FTIR, DSC, and in vitro and in vivo behavior. The 5% superdisintgrant showed good results. The FTIR and DSC study predicted no chemical interactions between the drug and excipients. The formulation containing xanthan gum showed drug retaining abilities, but failed to float. The tablet containing HPMC K15M showed a high swelling index. The lag time for the tablet coated with 200 mg carrageenan was 3±0.1 hrs with 99.99±1.5% drug release; with 140 mg HPMC K4M, the lag time was 3±0.1 hrs with 99.71±1.2% drug release; and with 120 mg HPMC K15M, the lag time was 3±0.2 hrs with 99.98±1.7% drug release. The release mechanism of the tablet followed the Korsmeyer-Peppas equation and a first-order release pattern. Floating and lag time behavior have shown good in vitro and in vivo correlations. PMID:24959410

Jagdale, Swati C; Suryawanshi, Vishnu M; Pandya, Sudhir V; Kuchekar, Bhanudas S; Chabukswar, Aniruddha R

2014-06-01

203

Pharmaceutical development of ondansetron tablets.  

PubMed

Ondansetron tablets contain ondansetron base as the hydrochloride dihydrate, lactose, microcrystalline cellulose, starch and magnesium stearate. Tablets sampled at the beginning and end of the compression process have good content uniformity and drug content, showing that there is no segregation or loss of the drug substance during tabletting. The release of drug substance is related to the tablet disintegration time. Tablets with disintegration times of 3 and 10 min release 85% of the drug substance in approximately 6 and 20 min respectively. Satisfactory bioavailability has been demonstrated. The tablets have good stability, and have a shelf life of 2 years when stored below 30 degrees C. PMID:2533901

Leak, R E; Woodford, J D

1989-01-01

204

What Floats Your Boat?  

NSDL National Science Digital Library

Students use modeling clay, a material that is denser than water and thus ordinarily sinks in water, to discover the principle of buoyancy. They begin by designing and building boats out of clay that will float in water, and then refine their designs so that their boats will carry as great a load (metal washers) as possible. Building a clay boat to hold as much weight as possible is an engineering design problem. Next, they compare amount of water displaced by a lump of clay that sinks to the amount of water displaced by the same lump of clay when it is shaped so as to float. Determining the masses of the displaced water allows them to arrive at Archimedes' principle, whereby the mass of the displaced water equals the mass of the floating clay boat.

Engineering K-Ph.d. Program

205

Floating nut retention system  

NASA Technical Reports Server (NTRS)

A floating nut retention system includes a nut with a central aperture. An inner retainer plate has an opening which is fixedly aligned with the nut aperture. An outer retainer member is formed of a base plate having an opening and a surface adjacent to a surface of the inner retainer plate. The outer retainer member includes a securing mechanism for retaining the inner retainer plate adjacent to the outer retainer member. The securing mechanism enables the inner retainer plate to float with respect to the outer retainer number, while simultaneously forming a bearing surface for inner retainer plate.

Charles, J. F.; Theakston, H. A. (inventors)

1980-01-01

206

Hawaii's Floating City Development Program.  

National Technical Information Service (NTIS)

Progress toward the engineering design, construction logistics, and the construction of large stable floating platforms is described. Plans to construct the first floating city are discussed and the planned utilization of the community described. For the ...

J. P. Craven J. A. Hanson

1972-01-01

207

Effect of ionic crosslink on the release of metronidazole from partially carboxymethylated guar gum tablet.  

PubMed

Partially carboxymethylated guar gum (PCMGG) was crosslinked in situ by Ca(2+) ions during wet massing step of tablet preparation. The resulting tablets were evaluated for the effect of the extent of crosslinking on drug release and matrix swelling. Increase in the concentration of Ca(2+) ions increased the viscosity of gel layer and reduced the water penetration velocity into the matrix with subsequent decrease in swelling of the tablets and drug release. Beyond a certain concentration of Ca(2+) ions, the viscosity of the gel layer decreased and the drug release rate increased primarily due to erosion of the matrix. The mechanism of drug release appeared to be non-Fickian or anomalous transport. The release data also best fitted in zero order equation. The model drug, metronidazole, was compatible with the matrix materials as evident from instrumental analyses. Such formulation may provide flexibility in achieving the desired drug release rate from crosslinked matrix tablets. PMID:24721097

Singh, Rakesh; Maity, Siddhartha; Sa, Biswanath

2014-06-15

208

Asset Float and Speculative Bubbles  

Microsoft Academic Search

We model the relationship between asset float (tradeable shares) and speculative bubbles. Investors with heterogeneous beliefs and short-sales constraints trade a stock with limited float because of insider lockups. A bubble arises as price overweighs optimists' beliefs and investors anticipate the option to resell to those with even higher valuations. The bubble's size depends on float as investors anticipate an

HARRISON HONG; JOSÉ SCHEINKMAN; WEI XIONG

2006-01-01

209

Corona from floating electrodes  

Microsoft Academic Search

It is not unusual to have insulated conducting objects located close to the conductors of a Lightning Protection System. However, the separation of these objects from the Lightning Protection System could vary from a few millimetres to some centimetres. When the system is exposed to thunderstorm electric fields, discharge could be initiated between the Lightning Protection System and the floating

Francisco Roman; Vernon Cooray; Viktor Scuka

1996-01-01

210

Float Technology Development.  

National Technical Information Service (NTIS)

It is the long-term goal of the principal investigators of this grant to develop profiling floats with expanded capabilities in terms of better sensors, communications methods, greater operating depths, and ice capability. The objective of this work is to...

D. Webb J. Nystuen N. Larson S. C. Riser

2003-01-01

211

Compound floating pivot micromechanisms  

SciTech Connect

A new class of tilting micromechanical mechanisms have been developed. These new mechanisms use compound floating pivot structures to attain far greater tilt angles than are practical using other micromechanical techniques. The new mechanisms are also capable of bi-directional tilt about multiple axes.

Garcia, Ernest J. (Albuquerque, NM)

2001-04-24

212

Floating Paper Clip  

NSDL National Science Digital Library

In this activity, challenge learners to float a paper clip in a cup of water. Learners discover that a paper clip will sink in a cup of water, except when it is placed on a piece of paper towel. Use this activity to demonstrate the principles of surface tension, adhesion/cohesion, and gravity.

Boston, Wgbh

2002-01-01

213

Floating Head Cup  

NSDL National Science Digital Library

In this activity, learners watch a figure "magically" float up through the air. Learners use 2 straws, a cup, rubber band, pipe cleaner, and piece of buoyant material to make a simple model of novel Chinese art pieces, which are typically made out of ceramics. Use this activity to demonstrate the relationship between density and buoyancy.

Workshop, Watsonville E.

2011-01-01

214

Root Beer Float  

NSDL National Science Digital Library

In this quick activity/demonstration about density, learners examine what happens when two cans of root beer--one diet and one regular--are placed in a large container of water. Do they sink or float? Use this activity to introduce learners to the importance of density as well as the nutritional content of soft drinks.

University, Colorado S.

2009-01-01

215

Vindolanda Tablets Online  

NSDL National Science Digital Library

Written in ink on postcard-sized sheets of wood, the Vindolanda tablets constitute a fascinating record of life in Roman Britain in the area of northern England around Hadrian's Wall during the first and second centuries AD. The tablets and the accompanying visual and printed materials were brought online through the collaborative efforts of the Centre for the Study of Ancient Documents and the Academic Computing Development Team at Oxford University. Visitors unfamiliar with the world of Roman Britain would do well to go first to the Exhibition section which contains helpful areas devoted to the world of military life during this period, the tablets themselves, and the excavations at Vindolanda. The Reference section also provides a great deal of context to the commentaries contained on the tablets, providing information about the military units in the Roman army and important dates and events in early Roman Britain. The heart of the site is dedicated to the tablets themselves, which may be browsed by number or searched by such variables as title, author, English translation, or commentary.

216

Compressibility of floating pellets with verapamil hydrochloride coated with dispersion Kollicoat SR 30 D.  

PubMed

The purpose of this study was to work out a method of compression of floating pellets with verapamil hydrochloride (VH) in a dose of 40 mg. It was assumed that this form should reside in the stomach floating for several hours and gradually release the drug in a controlled way. Compression of pellets into tablets, being a modern technological process, is much more perfect than enclosing them in a hard gelatin capsule. Kollicoat SR 30 D was selected for coating. In experiments three plasticizers were examined-propylene glycol, triethyl citrate and dibuthyl sebecate (all at concentration of 10%). It was found that VH release from pellets coated by the films of the same thickness (70 microm), however, containing plasticizers is considerably different. Pellets were prepared by wet granulation of powder mixture, spheronization of the granulated mass and coating of the cores with a sustained release film. Two kinds of cellulose, microcrystalline and powdered, and sodium hydrocarbonate were the main components of pellet core. Proper pellet coating film thickness, ensuring obtaining desirable VH release profile and flotation effect, was defined. X compositions of tablets with pellets were examined in order to obtain formulation, from which VH release would mostly approximate pellets before compressing. The best formulation was evaluated taking into account the effect of compression force an tablet hardness and friability, and pellet agglomeration and flotation. Tablet cross-section photographs were taken confirming necessary coating film thickness preventing their deformation caused by compressing into tablets. PMID:15848067

Sawicki, Wies?aw; Lunio, Rafa?

2005-05-01

217

Physical characterizations and sustained release profiling of gastroretentive drug delivery systems with improved floating and swelling capabilities.  

PubMed

The aim was to develop gastroretentive drug delivery systems (GRDDSs) by combining floating and swelling. GRDDS tablets formulated with hydroxyethylcellulose (HEC), chitosan (CS) and sodium bicarbonate (SB) for evaluating floating capacity (floating lag time and duration) and swelling characteristics. CS was used because it was swellable in acidic media and biocompatible. Losartan was incorporated into the optimized formulations for sustained release profiling. Results demonstrated that for those formulations at HEC:CS ratio of 5:5 containing CS, both the floating lag time and floating duration were optimal and reached the preferred swelling effect and sustain for 24h. Adding SB improved the floating capabilities for all ratios of HEC:CS, but reduced the swelling ability for those formulations containing a higher portion of low viscosity grade CS. Sustained release profiles for losartan in those formulations were achievable, using all viscosity grades of CS at all examined HEC:CS ratios; however, it is more adjustable at different HEC:CS ratios when using a lower viscosity grade of CS. Optimized GRDDS formulations for losartan composed of an equivalent ratio of HEC to CS with 20mg SB resulted in the tablets floating for more than 16 h and an adjustable sustained release profile. PMID:23237874

Chen, Ying-Chen; Ho, Hsiu-O; Lee, Tzu-Yu; Sheu, Ming-Thau

2013-01-30

218

Tablet Process Simulator  

NSDL National Science Digital Library

The North Carolina Community College System BioNetwork's interactive eLearning tools (IETs) are reusable chunks of training that can be deployed in a variety of courses or training programs. IETs are designed to enhance, not replace hands-on training. Learners are able to enter a hands-on lab experience better prepared and more confident. This particular IET is a Tablet Process Simulator in which visitors set up and run a tablet press in a virtual 3D environment. The tool requires the program to be downloaded and installed, and gives helpful installation instructions. Users will start by downloading a zip file to their computer.

2013-07-23

219

Development of oral acetaminophen chewable tablets with inhibited bitter taste.  

PubMed

Various formulations with some matrix bases and corrigents were examined for development of oral chewable tablets which suppressed the bitter taste of acetaminophen, often used as an antipyretic for infants. Corn starch/lactose, cacao butter and hard fat (Witepsol H-15) were used for matrix bases, and sucrose, cocoa powder and commercial bitter-masking powder mixture made from lecithin (Benecoat BMI-40) were used for corrigents against bitter taste. The bitter taste intensity was evaluated using volunteers by comparison of test samples with standard solutions containing quinine at various concentrations. For the tablets made of matrix base and drug, Witepsol H-15 best inhibited the bitter taste of the drug, and the bitter strength tended to be suppressed with increase in the Witepsol H-15 amount. When the inhibitory effect on the bitter taste of acetaminophen solution was compared among the corrigents, each tended to suppress the bitter taste; especially, Benecoat BMI-40 exhibited a more inhibitory effect. Further, chewable tablets were made of one matrix base and one corrigent, and of one matrix base and two kinds of corrigents, their bitter taste intensities after chewing were compared. As a result, the tablets made of Witepsol H-15/Benecoat BMI-40/sucrose, of Witepsol H-15/cocoa powder/sucrose and of Witepsol H-15/sucrose best masked the bitter taste so that they were tolerable enough to chew and swallow. The dosage forms best masking bitter taste showed good release of the drug, indicating little change in bioavailability by masking. PMID:12527182

Suzuki, Hiroyuki; Onishi, Hiraku; Takahashi, Yuri; Iwata, Masanori; Machida, Yoshiharu

2003-01-30

220

Freely floating smectic films.  

PubMed

We have investigated the dynamics of freely floating smectic bubbles using high-speed optical imaging. Bubbles in the size range from a few hundred micrometers to several centimeters were prepared from collapsing catenoids. They represent ideal model systems for the study of thin-film fluid dynamics under well-controlled conditions. Owing to the internal smectic layer structure, the bubbles combine features of both soap films and vesicles in their unique shape dynamics. From a strongly elongated initial shape after pinch-off, they relax towards the spherical equilibrium, first by a slow redistribution of the smectic layers, and finally by weak, damped shape oscillations. In addition, we describe the rupture of freely floating smectic bubbles, and the formation and stability of smectic filaments. PMID:24692347

May, Kathrin; Harth, Kirsten; Trittel, Torsten; Stannarius, Ralf

2014-05-19

221

Serial floating point formatter  

SciTech Connect

A floating point formatter for changing fixed point serial digital data, such as that received by a seismic data acquisition system, is disclosed wherein fixed point serial digital data is received and scaled to remove any bias added by preamplification. The scaled data is shifted a predetermined number of bits and a resulting exponent is calculated. The shifted data signal and corresponding exponent are combined and further scaled to permit stacking the data without exceeding the system capacity.

Peterson, R. D.; Penner, W. A.

1985-11-12

222

CES 2011: Tablet Crazy  

ERIC Educational Resources Information Center

Ereaders are so last year. Tablets were the watchword at this year's annual Consumer Electronics Show (CES) in Las Vegas, January 6-9. This year, the show set new records, with some 2700 companies from around the world exhibiting at the multiple exhibition halls and 30,000 attendees gawking at the products. What did they see? There were still some…

Rapp, David

2011-01-01

223

Bioavailability of prednisolone tablets  

Microsoft Academic Search

Two fourtreatment crossover studies were performed using 12 adult male volunteers in each with seven different commercially available prednisolone tablets. Plasma samples were assayed for prednisolone by a radioimmunoassay method. Statisacal analyses of the data, by analysis of variance for crossover design (ANOVA), showed no significant differences among the treatment averages at any of the sampling times except at 0.25

Aubrey V. Tembo; Margarette R. Hallmark; Ermelinda Sakmar; Hannelore G. Bachmaan; Donald J. Weidler; John G. Wagner

1977-01-01

224

Tableting of coated pellets  

Microsoft Academic Search

Oral sustained\\/controlled release multiple unit dosage forms are becoming more popular when compared to single unit dosage forms. With regard to the final dosage form, the multiparticulates are usually formulated into single unit dosage forms such as filling them into hard gelatin capsules or compacting them into tablets. Although there is abundant literature available on the preparation of pellets and

Roland Bodmeier

1997-01-01

225

Hope floats: an orthopaedic tip sheet for float pool nurses.  

PubMed

A common method to address staffing shortages is the use of float nurses. This short-term resolution is not without its issues. When float nurses are unfamiliar with the assigned patient population or when there is little time for unit orientation, unnecessary anxiety and undue stress can affect the staff, healthcare providers, and, most importantly, the patients. Developing creative and informative tools to guide the float nurse during their shift can be beneficial to all involved. PMID:21597351

Roach, Janey A; Tremblay, Lisa M; Carter, Jessica

2011-01-01

226

WindFloat: A floating foundation for offshore wind turbines  

Microsoft Academic Search

This manuscript summarizes the feasibility study conducted for the WindFloat technology. The WindFloat is a three-legged floating foundation for multimegawatt offshore wind turbines. It is designed to accommodate a wind turbine, 5 MW or larger, on one of the columns of the hull with minimal modifications to the nacelle and rotor. Potential redesign of the tower and of the turbine

Dominique Roddier; Christian Cermelli; Alexia Aubault; Alla Weinstein

2010-01-01

227

Imperatorin sustained-release tablets: In vitro and pharmacokinetic studies.  

PubMed

We prepared and evaluated imperatorin (IMP) sustained-release tablets. IMP is an active compound in Angelica dahuricae, a Chinese herbal medicine. We used different polymers, such as hydroxypropyl methylcellulose (HPMC K4M, K15M, and K100M), carbopol 934P, sodium carboxymethyl cellulose (CMC-Na), and their combinations to prepare the matrix tablets and achieve the desired sustained release profile. The in vitro release profiles of these formulations were examined and fit to various kinetic release models. We also tested the effects of polymer combination ratios on the in vitro release rate. In vivo studies were performed for the optimized formulation in six beagle dogs, and pharmacokinetic parameters were compared with plain IMP tablets. IMP sustained-release tablets exhibited a more sustained plasma concentration than the plain tablets, with a relative bioavailability of 127.25%. The in vitro releases rates and in vivo absorption correlated for the initial 8 hours. These results demonstrate that the sustained-release tablet system can effectively control the release of IMP. PMID:20803124

Pan, Jingjing; Lu, Wen; Li, Changhui; Wang, Sicen; He, Langchong

2010-08-01

228

Modifying drug release and tablet properties of starch acetate tablets by dry powder agglomeration.  

PubMed

In this study three model drugs (N-acetyl-D-glucosamine (NAG), anhydrous caffeine, and propranolol hydrochloride) were agglomerated with starch acetate (SA) by mixing the binary powders on a stainless steel (SS) plate. Agglomeration was induced by triboelectrification of the particles during mixing, and it was evaluated as a method to achieve controlled drug release rate. These agglomerates, mixed with different amounts of a disintegrant, were compressed into tablets whose dissolution characteristics were determined. Triboelectric measurements showed that when the drugs were in contact with SS, charges of the opposite polarity were generated to SA (+) and caffeine and NAG (-) promoting adhesion. Instead, propranolol HCl was charged with the same polarity as SA. SEM micrographs showed that smaller caffeine particles, in spite of their larger negative charge, agglomerated less efficiently with SA than larger NAG particles. This emphasizes the importance of particle size in the agglomeration process. Propranolol HCl did not form agglomerates with SA since their particle sizes and charges were identical. As a result, agglomeration of powders prior to tablet compression allows for modification and control of the release rate of the drugs from the SA matrix tablets as well as the tensile strength of the tablets. PMID:17075868

Mäki, Riikka; Suihko, Eero; Rost, Susanne; Heiskanen, Minna; Murtomaa, Matti; Lehto, Vesa-Pekka; Ketolainen, Jarkko

2007-02-01

229

Automatic Generation of Floating-Point Test Data  

Microsoft Academic Search

For numerical programs, or more generally for programs with floating-point data, it may be that large savings of time and storage are made possible by using numerical maximization methods instead of symbolic execution to generate test data. Two examples, a matrix factorization subroutine and a sorting method, illustrate the types of data generation problems that can be successfully treated with

Webb Miller; David L. Spooner

1976-01-01

230

Tableting and tablet properties of alginates: characterisation and potential for Soft Tableting.  

PubMed

The aim of the study was to evaluate the suitability of alginates for Soft Tableting. For this purpose the compaction properties of alginates, varying in molecular weight, guluronic acid/mannuronic acid ratio and salt, were investigated and compared to MCC. Based on the mechanical properties, the suitability of the tested excipients for Soft Tableting was predicted. In order to test the prediction the tested materials were used to tablet enteric coated pellets, which served as a pressure sensitive material. The tableting behaviour was analysed by the 3-D modeling technique. The tablet properties were analysed by determining the elastic recovery and the compactibility. Alginates in general deformed elastically. The compression behaviour depended on the chemical composition of the alginates with sodium alginates being more elastic than potassium alginates. Tablets containing alginates with low guluronic acid content exhibited higher elasticity than tablets with alginates having a low mannuronic acid content. The plasticity of potassium alginates was higher than for sodium alginates. However, the plasticity of all tested alginates was lower than the plasticity of MCC. The compactibility of the tested alginates was sufficient. The proposed prediction, which states that tableting excipients with higher elasticity are more suitable for tableting sensitive materials than plastic excipients, was valid for the tested materials. The elastic alginates inflicted less damage on the pellets than the plastic MCC. Thus, all alginates were more appropriate for tableting pressure sensitive materials than MCC. PMID:18992337

Schmid, Wolfgang; Picker-Freyer, Katharina M

2009-05-01

231

21 CFR 520.928 - Firocoxib tablets.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Firocoxib tablets. 520.928 Section 520...FORM NEW ANIMAL DRUGS § 520.928 Firocoxib tablets. (a) Specifications ...tablet contains 57 or 227 milligrams (mg) firocoxib. (b) Sponsor . See No....

2010-04-01

232

21 CFR 520.928 - Firocoxib tablets.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Firocoxib tablets. 520.928 Section 520...FORM NEW ANIMAL DRUGS § 520.928 Firocoxib tablets. (a) Specifications ...tablet contains 57 or 227 milligrams (mg) firocoxib. (b) Sponsor . See No....

2009-04-01

233

Will It Float?  

NSDL National Science Digital Library

Student preconceptions are one of the greatest challenges we face as science teachers. This Predict, Explain, Observe, and Explain (PEOE) activity challenges students? preconceived notions about why matter floats or sinks when placed in a liquid. The idea behind this model is to do a demonstration that first confirms student's conceptions followed by a second, similar demonstration that provides discrepant information creating cognitive dissonance. Learning happens as students are forced to modify their conceptions so that their view of how things work is not in conflict with what they are seeing.

Major, Jeff

2006-01-01

234

Design and evaluation of a dry coated drug delivery system with floating-pulsatile release.  

PubMed

The objective of this work was to develop and evaluate a floating-pulsatile drug delivery system intended for chronopharmacotherapy. Floating-pulsatile concept was applied to increase the gastric residence of the dosage form having lag phase followed by a burst release. To overcome limitations of various approaches for imparting buoyancy, we generated the system which consisted of three different parts, a core tablet, containing the active ingredient, an erodible outer shell and a top cover buoyant layer. The dry coated tablet consists in a drug-containing core, coated by a hydrophilic erodible polymer which is responsible for a lag phase in the onset of pulsatile release. The buoyant layer, prepared with Methocel K4M, Carbopol 934P and sodium bicarbonate, provides buoyancy to increase the retention of the oral dosage form in the stomach. The effect of the hydrophilic erodible polymer characteristics on the lag time and drug release was investigated. Developed formulations were evaluated for their buoyancy, dissolution and pharmacokinetic, as well gamma-scintigraphically. The results showed that a certain lag time before the drug released generally due to the erosion of the dry coated layer. Floating time was controlled by the quantity and composition of the buoyant layer. Both pharmacokinetic and gamma-scintigraphic data point out the capability of the system of prolonged residence of the tablets in the stomach and releasing drugs after a programmed lag time. PMID:17803198

Zou, Hao; Jiang, Xuetao; Kong, Lingshan; Gao, Shen

2008-01-01

235

Genetics Home Reference: Floating-Harbor syndrome  

MedlinePLUS

... PubMed Recent literature OMIM Genetic disorder catalog Conditions > Floating-Harbor syndrome On this page: Description Genetic changes ... names Glossary definitions Reviewed December 2012 What is Floating-Harbor syndrome? Floating-Harbor syndrome is a disorder ...

236

A floating prolate spheroid.  

PubMed

The equilibrium position of a spherical or prolate spheroidal particle resembling a needle floating at the interface between two immiscible fluids is discussed. A three-dimensional meniscus attached to an a priori unknown contact line at a specified contact angle is established around the particle, imparting to the particle a capillary force due to surface tension that is balanced by the buoyancy force and the particle weight. An accurate numerical solution for a floating sphere is obtained by solving a boundary-value problem, and the results are compared favorably with an approximate solution where the effect of the particle surface curvature is ignored and the elevation of the contact line is computed using an analytical solution for the meniscus attached to an inclined flat plate. The approximate formulation is applied locally around the nearly planar elliptical contact line of a prolate spheroid to derive a nonlinear algebraic equation governing the position of the particle center and the mean elevation of the contact line. The effect of the fluid and particle densities, contact angle, and capillary length is discussed, and the shape of the contact line is reconstructed and displayed from the local solution. PMID:21889165

Pozrikidis, C

2011-12-01

237

Floating offshore structure  

SciTech Connect

A floating offshore structure which is moored at a fixed position on the sea by means of mooring hawsers and anchors connected to the ends thereof respectively for conducting a submarine excavating operation from a deck of the structure. The structure includes a moorage hull part provided with a vertical through-hole formed therein for receiving an excavating drill pipe and the mooring hawsers and a movable hull part connected to the moorage hull part so as to be rotatable within a horizontal plane. The movable hull part is constituted as a hull defining the outer wall of the floating offshore structure and connected with the moorage hull part by inserting it into a moorage hull part receiving hole formed at a position closer to the bow thereof. The movable hull part has near its water plane a horizontal section with a substantially oval shape formed by a fore draft part in a substantially circular or polygonal shape, with the moorage hull part receiving hole as a center and an after draft part taperingly projecting aft from the fore draft part.

Oshima, M.; Narita, H.; Tabuchi, H.; Yashima, N.

1985-05-28

238

Formulation and Evaluation of Floating Oral In Situ Gelling System of Amoxicillin  

PubMed Central

Purpose. Effective Helicobacter pylori eradication requires delivery of the antibiotic locally in the stomach. High dose of amoxicillin (750 to 1000?mg) is difficult to incorporate in floating tablets but can easily be given in liquid dosage form. Keeping the above facts in mind, we made an attempt to develop a new floating in situ gelling system of amoxicillin with increased residence time using sodium alginate as gelling polymer to eradicate H. pylori. Methods. Floating in situ gelling formulations were prepared using sodium alginate, calcium chloride, sodium citrate, hydroxypropyl methyl cellulose K100, and sodium bicarbonate. The prepared formulations were evaluated for solution viscosity, floating lag time, total floating time, and in vitro drug release. The formulation was optimized using a 32 full factorial design. Dissolution data were fitted to various models to ascertain kinetic of drug release. Regression analysis and analysis of variance were performed for dependent variables. Results. All formulations (F1–F9) showed floating within 30?s and had total floating time of more than 24?h. All the formulations showed good pourability. It was observed that concentration of sodium alginate and HPMC K100 had significant influence on floating lag time, cumulative percentage drug release in 6?h and 10?h. The batch F8 was considered optimum since it showed more similarity in drug release (f2 = 74.38) to the theoretical release profile. Conclusion. Floating in situ gelling system of amoxicillin can be formulated using sodium alginate as a gelling polymer to sustain the drug release for 10 to 12?h with zero-order release kinetics.

Patel, Dasharath M.; Patel, Divyesh K.; Patel, Chhagan N.

2011-01-01

239

Floating, surface liquids retrieval system  

Microsoft Academic Search

A floating retriever is described for retrieving, for example, spilled oil or other liquid substances on the top of water having a central liquid collection chamber with a vacuum or suction pick-up for delivery of the pollutants to a mother vessel which controls the retriever by means of a boom structure. The retriever has a large surrounding circular float with

1980-01-01

240

Does It Sink or Float?  

ERIC Educational Resources Information Center

This activity is designed to teach prekindergarten to second grade students about the concept of sink or float through an inquiry activity. Students will use familiar objects to predict and test the properties of sink and float. Background information is offered to teachers to assist them with this activity. This lesson begins with an engaging…

McDonald, Judith Richards

2012-01-01

241

Floating roof storage tank boilover  

Microsoft Academic Search

Storage tanks are important facilities for the major hazard installations (MHIs) to store large quantity of crude oil. There is several fire types can occur with large diameter open top floating roof storage tanks. Boilover is considered one of the most dangerous fires in large-scale oil tank. The world has witnessed many incidents due to boilover in floating roof storage

Ibrahim M. Shaluf; Salim A. Abdullah

2011-01-01

242

Code check floating tank roofs  

Microsoft Academic Search

This paper reports that both API 650 and BS 2654 contain criteria for design of single deck pontoon-type tank floating roofs. The codes states that the floating roof shall have sufficient buoyancy to remain afloat under the following conditions: tank content specific gravity is 0.7; the roof center deck is punctured; any two adjacent pontoon compartments are punctured; no water

Hassan

1992-01-01

243

What Makes a Boat Float?  

NSDL National Science Digital Library

Whether or not a boat floats is determined by its shape and density. In this activity, students discover how and why boats float by designing different hull shapes and finding which design holds the most weight. Students record, calculate, and interpret data as they learn about buoyancy in this hands-on activity.

Eichinger, John

2009-05-01

244

Mirage of Floating Exchange Rates  

Microsoft Academic Search

This note summarizes some of the highlights of my longer paper with Guillermo Calvo”Fear of Floating.” Many emerging market countries have suffered financial crises. One view blames soft pegs for these crises. Adherents to that view suggest that countries move to corner solutions--hard pegs or floating exchange rates. We analyze the behavior of exchange rates, reserves, and interest rates to

Carmen M. Reinhart

2000-01-01

245

Application of Design of Experiment for Floating Drug Delivery of Tapentadol Hydrochloride  

PubMed Central

The aim of the present study was to apply design of experiment (DOE) to optimize floating drug delivery of tapentadol hydrochloride. Tapentadol hydrochloride is a synthetic opioid used as a centrally acting analgesic and effective in both experimental and clinical pain. The half-life of the drug is about 4 hours and oral dose is 50 to 250?mg twice a day. For optimization 32 full factorial design was employed for formulation of tapentadol hydrochloride tablets. Sodium bicarbonate was incorporated as a gas-generating agent. Combination of polymers Xanthan gum and Locust bean gum was used to achieve controlled release effect. The concentration of polymers was considered as the independent variables and dependent variables were floating lag time and swelling index of the tablets. From the factorial batches, it was observed that formulation containing combination of 20% sodium bicarbonate and 10% citric acid shows optimum floating ability whereas the formulation containing 20% Xanthan gum and 28% Locust bean gum shows optimum sustained drug release pattern with adequate floating.

Jagdale, Swati C.; Patil, Somnath; Kuchekar, Bhanudas S.

2013-01-01

246

Floating treatment wetlands for domestic wastewater treatment.  

PubMed

Floating islands are a form of treatment wetland characterized by a mat of synthetic matrix at the water surface into which macrophytes can be planted and through which water passes. We evaluated two matrix materials for treating domestic wastewater, recycled plastic and recycled carpet fibers, for chemical oxygen demand (COD) and nitrogen removal. These materials were compared to pea gravel or open water (control). Experiments were conducted in laboratory scale columns fed with synthetic wastewater containing COD, organic and inorganic nitrogen, and mineral salts. Columns were unplanted, naturally inoculated, and operated in batch mode with continuous recirculation and aeration. COD was efficiently removed in all systems examined (>90% removal). Ammonia was efficiently removed by nitrification. Removal of total dissolved N was ?50% by day 28, by which time most remaining nitrogen was present as NO(3)-N. Complete removal of NO(3)-N by denitrification was accomplished by dosing columns with molasses. Microbial communities of interest were visualized with denaturing gradient gel electrophoresis (DGGE) by targeting specific functional genes. Shifts in the denitrifying community were observed post-molasses addition, when nitrate levels decreased. The conditioning time for reliable nitrification was determined to be approximately three months. These results suggest that floating treatment wetlands are a viable alternative for domestic wastewater treatment. PMID:22105133

Faulwetter, J L; Burr, M D; Cunningham, A B; Stewart, F M; Camper, A K; Stein, O R

2011-01-01

247

Floating Silicon Method  

SciTech Connect

The Floating Silicon Method (FSM) project at Applied Materials (formerly Varian Semiconductor Equipment Associates), has been funded, in part, by the DOE under a “Photovoltaic Supply Chain and Cross Cutting Technologies” grant (number DE-EE0000595) for the past four years. The original intent of the project was to develop the FSM process from concept to a commercially viable tool. This new manufacturing equipment would support the photovoltaic industry in following ways: eliminate kerf losses and the consumable costs associated with wafer sawing, allow optimal photovoltaic efficiency by producing high-quality silicon sheets, reduce the cost of assembling photovoltaic modules by creating large-area silicon cells which are free of micro-cracks, and would be a drop-in replacement in existing high efficiency cell production process thereby allowing rapid fan-out into the industry.

Kellerman, Peter

2013-12-21

248

Orally Disintegrating Tablets: A Review  

Microsoft Academic Search

Drug delivery systems are becoming increasingly sophisticated as pharmaceutical scientists acquire a better understanding of the physicochemical and biochemical parameters pertinent to their performance. Over the past three decades, orally disintegrating tablets (ODTs) have gained considerable attention as a preferred alternative to conventional tablets and capsules due to better patient compliance. ODTs are solid dosage forms containing medicinal substances which

Jaysukh J Hirani; Dhaval A Rathod; Kantilal R Vadalia

249

Review of bilayer tablet technology.  

PubMed

Therapeutic strategies based on oral delivery of bilayer (and multilayer) tablets are gaining more acceptance among brand and generic products due to a confluence of factors including advanced delivery strategies, patient compliance and combination therapy. Successful manufacturing of these ever more complex systems needs to overcome a series of challenges from formulation design to tablet press monitoring and control. This article provides an overview of the state-of-the-art of bilayer tablet technology, highlighting the main benefits of this type of oral dosage forms while providing a description of current challenges and advances toward improving manufacturing practices and product quality. Several aspects relevant to bilayer tablet manufacturing are addressed including material properties, lubrication, layer ordering, layer thickness, layer weight control, as well as first and final compression forces. A section is also devoted to bilayer tablet characterization that present additional complexities associated with interfaces between layers. The available features of the manufacturing equipment for bilayer tablet production are also described indicating the different strategies for sensing and controls offered by bilayer tablet press manufacturers. Finally, a roadmap for bilayer tablet manufacturing is advanced as a guideline to formulation design and selection of process parameters and equipment. PMID:24370841

Abebe, Admassu; Akseli, Ilgaz; Sprockel, Omar; Kottala, Niranjan; Cuitiño, Alberto M

2014-01-30

250

21 CFR 520.1510 - Nitenpyram tablets.  

Code of Federal Regulations, 2010 CFR

...nitenpyram tablets and flavored milbemycin/lufenuron tablets as in paragraph (d)(1...of this section with either flavored lufenuron tablets as in § 520.1288(c)(1) of this chapter or flavored milbemycin and lufenuron tablets as in §...

2010-04-01

251

21 CFR 520.1510 - Nitenpyram tablets.  

Code of Federal Regulations, 2010 CFR

...nitenpyram tablets and flavored milbemycin/lufenuron tablets as in paragraph (d)(1...of this section with either flavored lufenuron tablets as in § 520.1288(c)(1) of this chapter or flavored milbemycin and lufenuron tablets as in §...

2009-04-01

252

21 CFR 520.1200 - Ivermectin, fenbendazole, and praziquantel tablets.  

Code of Federal Regulations, 2013 CFR

...Ivermectin, fenbendazole, and praziquantel tablets. 520.1200 Section 520.1200 Food...Ivermectin, fenbendazole, and praziquantel tablets. (a) Specifications . Each chewable tablet contains either: (1) 68...

2013-04-01

253

21 CFR 520.623 - Diethylcarbamazine citrate, oxibendazole chewable tablets.  

Code of Federal Regulations, 2013 CFR

...false Diethylcarbamazine citrate, oxibendazole chewable tablets. 520.623 Section 520.623 Food and Drugs...623 Diethylcarbamazine citrate, oxibendazole chewable tablets. (a) Specifications. Each tablet...

2013-04-01

254

21 CFR 520.623 - Diethylcarbamazine citrate, oxibendazole chewable tablets.  

Code of Federal Regulations, 2010 CFR

...false Diethylcarbamazine citrate, oxibendazole chewable tablets. 520.623 Section 520.623 Food and Drugs...623 Diethylcarbamazine citrate, oxibendazole chewable tablets. (a) Specifications. Each tablet...

2009-04-01

255

Design and in vitro evaluation of zidovudine oral controlled release tablets prepared using hydroxypropyl methylcellulose.  

PubMed

Oral controlled release matrix tablets of zidovudine were prepared using different proportions and different viscosity grades of hydroxypropyl methylcellulose. The effect of various formulation factors like polymer proportion, polymer viscosity and compression force on the in vitro release of drug were studied. In vitro release studies were carried out using United States Pharmacopeia (USP) type 1 apparatus (basket method) in 900 ml of pH 6.8 phosphate buffer at 100 rpm. The release kinetics were analyzed using Zero-order model equation, Higuchi's square-root equation and Ritger-Peppas' empirical equation. Compatibility of drug with various formulations excipients used was studied. In vitro release studies revealed that the release rate decreased with increase in polymer proportion and viscosity grade. Increase in compression force was found to decrease the rate of drug release. Matrix tablets containing 10% hydroxypropyl methylcellulose (HPMC) 4000 cps were found to show a good initial drug release of 21% in the first hour and extended the release upto 16 h. Matrix tablets containing 20% HPMC 4000 cps and 10% HPMC 15000 cps showed a first hour release of 18% and extended the release upto 20 h. Mathematical analysis of the release kinetics indicated that the nature of drug release from the matrix tablets followed non-Fickian or anomalous release. No incompatibility was observed between the drug and excipients used in the formulation of matrix tablets. The developed controlled release matrix tablets of zidovudine, with good initial release (17-25% in first hour) and which extend the release upto 16-20 h, can overcome the disadvantages of conventional tablets of zidovudine. PMID:18379101

Ravi, Punna Rao; Ganga, Sindhura; Saha, Ranendra Narayan

2008-04-01

256

Extra-strong "floating nut"  

NASA Technical Reports Server (NTRS)

Increased bearing area withstands much higher torque than previous designs. Floating nut makes it possible to fasten parts on heavy-duty equipment, such as tractors and cranes, even though they can be reached for tightening from one side only.

Charles, J. F.; Theakston, H.

1979-01-01

257

Code check floating tank roofs  

SciTech Connect

This paper reports that both API 650 and BS 2654 contain criteria for design of single deck pontoon-type tank floating roofs. The codes states that the floating roof shall have sufficient buoyancy to remain afloat under the following conditions: tank content specific gravity is 0.7; the roof center deck is punctured; any two adjacent pontoon compartments are punctured; no water or live loads are present; and the roof primary drain is inoperative.

Hassan, H.M.K. (Abu Dhabi Marine Operating Co. (United Arab Emirates))

1992-10-01

258

Floating into Thin Air  

SciTech Connect

On May 18, 2005, a giant helium balloon carrying the High Energy Focusing Telescope (HEFT) sailed into the spring sky over the deserts of New Mexico. The spindly steel and aluminum gondola that houses the optics, detectors, and other components of the telescope floated for 25 hours after its launch from Fort Sumner, New Mexico. For 21 of those hours, the balloon was nearly 40 kilometers above Earth's surface--almost four times higher than the altitude routinely flown by commercial jet aircraft. In the upper reaches of Earth's atmosphere, HEFT searched the universe for x-ray sources from highly energetic objects such as binary stars, galaxy clusters, and supermassive black holes. Before landing in Arizona, the telescope observed and imaged a dozen scientific targets by capturing photons emitted from these objects in the high-energy (hard) x-ray range (above 10 kiloelectronvolts). Among these targets were the Crab synchrotron nebula, the black hole Cygnus X-1 (one of the brightest x-ray sources in the sky), and the blazar 3C454.3. The scientific data gathered from these targets are among the first focused hard x-ray images returned from high altitudes.

Hazi, A U

2007-02-06

259

Skylab floating ice experiment  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Coupling of the aircraft data with the ground truth observations proved to be highly successful with interesting results being obtained with IR and SLAR passive microwave techniques, and standard photography. Of particular interest were the results of the PMIS system which operated at 10.69 GHz with both vertical and horizontal polarizations. This was the first time that dual polarized images were obtained from floating ice. In both sea and lake ice, it was possible to distinguish a wide variety of thin ice types because of their large differences in brightness temperatures. It was found that the higher brightness temperature was invariably obtained in the vertically polarized mode, and as the age of the ice increases the brightness temperature increases in both polarizations. Associated with this change in age, the difference in temperature was observed as the different polarizations decreased. It appears that the horizontally polarized data is the most sensitive to variations in ice type for both fresh water and sea ice. The study also showed the great amount of information on ice surface roughness and deformation patterns that can be obtained from X-band SLAR observations.

Campbell, W. J. (principal investigator); Ramseier, R. O.; Weaver, R. J.; Weeks, W. F.

1975-01-01

260

Floating wind turbine system  

NASA Technical Reports Server (NTRS)

A floating wind turbine system with a tower structure that includes at least one stability arm extending therefrom and that is anchored to the sea floor with a rotatable position retention device that facilitates deep water installations. Variable buoyancy for the wind turbine system is provided by buoyancy chambers that are integral to the tower itself as well as the stability arm. Pumps are included for adjusting the buoyancy as an aid in system transport, installation, repair and removal. The wind turbine rotor is located downwind of the tower structure to allow the wind turbine to follow the wind direction without an active yaw drive system. The support tower and stability arm structure is designed to balance tension in the tether with buoyancy, gravity and wind forces in such a way that the top of the support tower leans downwind, providing a large clearance between the support tower and the rotor blade tips. This large clearance facilitates the use of articulated rotor hubs to reduced damaging structural dynamic loads. Major components of the turbine can be assembled at the shore and transported to an offshore installation site.

Viterna, Larry A. (Inventor)

2009-01-01

261

Floating biological contactor  

SciTech Connect

A method is described using biological microorganisms for removing selected biodegradable materials from a pond or similar body of water, comprising the steps of: analyzing a sample of said pond water to determine at least one type of microorganism appropriate for feeding on said selected materials; fixing a plurality of bio-suspension elements within an enclosure which is floating at least partially submerged in said water body, said elements providing surfaces for supporting the growth of films of biological microorganisms; introducing said appropriate microorganisms into said enclosure along with discrete amounts of said pond water for growing colonies of said appropriate microorganisms on said biosuspension elements while circulation or other motion of said pond water is minimized in said enclosure; sampling, testing, and analyzing the water and microorganisms in said enclosure, and nurturing the growth of said microorganisms until large and stable colonies of said microorganisms have been established on said bio-suspension elements; and, thereafter, circulating pond water gently and regularly through and around said stable colony of appropriate microorganisms in said enclosure and returning said circulated water to the pond.

DiClemente, L.M.; Pickering, J.W. Wansea, R.M.

1993-07-20

262

Floating Tip Nanolithography  

NASA Astrophysics Data System (ADS)

We introduce a new mode of operation to standard atomic force microscopes, working under ambient conditions, for truly noncontact nanolithography. A phase-locked loop, based on tiny oscillations (<1 nm) of the cantilever at a frequency far from its mechanical resonance, is used to maintain the gap between the tip and the sample at a predetermined value of 1 - 4 nanometers continuously for long times without the tip ever touching the surface. In a geometry characteristic for Apertureless Scanning Near Field Optical Microscope, the tip is illuminated by a focused beam of a femtosecond laser (800 nm, 20 fsec, 100 mw ) for nano-patterning of the area under the tip. Under the laser irradiation the tip apex heats to a few hunderd degrees as verified by a direct measurement of Raman line shifts, and the elecrtomagnetic enhancement under the tip is used when the laser irradiates the actual tip apex. We demonstrate Floating Tip Nanolithography of two different types, both with lateral resolution of 10-20 nm. With a hot tip (the laser is not in contact with the surface) we thermally pattern the surface of a polymer film, and based on the electromagnetic field enhancement under the sharp tip we ablate narrow lines on a gold film. Future applications will be discussed.

Prior, Yehiam; Zhang, Kaiyin; Milner, Alexander; Karpovski, Michael

2008-03-01

263

Equivalence of the floating frame of reference approach and finite element formulations  

Microsoft Academic Search

The floating frame of reference formulation which is widely used in flexible multibody simulations leads to a highly non-linear inertia matrix. This matrix which exhibits a strong inertia coupling between the reference motion and the elastic deformation can be expressed in terms of a unique set of inertia shape integrals that depend on the assumed displacement field. In this paper,

A. A. Shabana; R. Schwertassek

1998-01-01

264

Bioequivalence study of ranitidine tablet  

Microsoft Academic Search

A bioequivalence study of ranitidine tablets was conducted according to the Korean Guidline for the Bioequivalence Test using\\u000a twelve healthy male subjects. The plasma concentration-time curves of ranitidine from the test and reference tablets showed\\u000a profound multiple peak phenomenon in each, subject as reported earlier. However, the area under the plasma concentration-time\\u000a curve (AUC) and the maximum plasma concentration at

Chang-Koo Shimw; Jae-Sun Hong; Chang-Ki Lee; Ik-Soo Han; Kwang-Sik Choi

1990-01-01

265

Stability of amlodipine besylate and atenolol in multi-component tablets of mono-layer and bi-layer types.  

PubMed

Multi-drug tablets of amlodipine besylate and atenolol were prepared as either mono-layer (mixed matrix) or bilayer tablets containing each drug in a separate layer by using similar excipients and processing. Each tablet batch was packed in strip and blister packs and kept under accelerated temperature and humidity conditions. The stability of two tablet and packaging types was compared by HPLC analysis after 0, 1, 3 and 4.5 months and expressed as the content of intact amlodipine and atenolol. The content of atenolol did not decline regardless of tablet and packaging type. Amlodipine content in bi-layer tablets decreased to about 95 and 88% when packed in strips and blisters, respectively. When prepared as mono-layer tablets, the content decreased to 72 and 32%, respectively.The study revealed that the bi-layer tablet formulation was more stable than the mono-layer type. Further, the stability was increased when the tablets were packed in aluminium strips as compared to PVC blisters. PMID:19103566

Aryal, Sajjan; Skalko-Basnet, Natasa

2008-09-01

266

Development and optimization of press coated floating pulsatile drug delivery of sumatriptan succinate.  

PubMed

Floating pulsatile is combined approach designed according to circadian rhythm to deliver the drug at right time, in right quantity and at right site as per pathophysiological need of disease with prolong gastric residence and lag phase followed by burst release. As the migraine follows circadian rhythm in which headache is more painful at the awakening time, the dosage form should be given during night time to release drug when pain get worsen. Present work deals with formulation and optimization of floating pulsatile tablet of sumatriptan succinate. Core tablet containing crospovidone as superdisintegrant (10%) showed burst release. Lag time was maintained using swellable polymer as polyoxN12K and xanthum gum. 3(2) experimental design was carried out. Developed formulations were evaluated for physical characteristics, in vitro and in vivo study. Optimized batch F2 with concentration of polyox N12K (73.43%) and xanthum gum (26.56%) of total polymer weight showed floating lag time 15±2 sec, drug content 99.58±0.2 %, hardness 6±0.2 Kg/cm(2) and drug release 99.54±2% with pulsatile manner followed lag period of 7±0.1h. In vivo x-ray study confirms prolong gastric residence of system. Programmable pulsatile release has been achieved by formulation F2 which meet demand of chronotherapeutic objective of migraine. PMID:24893996

Jagdale, Swati C; Pawar, Chandrakala R

2014-01-01

267

Fresh look at floating shock fitting  

NASA Technical Reports Server (NTRS)

A fast implicit upwind procedure for the two-dimensional Euler equations is described that allows accurate computations of shocked flows on nonadapted meshes. Away from shocks, the second-order accurate upwinding is based on the split-coefficient-matrix (SCM) method. In the presence of shocks, the difference stencils are modified using a floating shock fitting technique. Rapid convergence to steady-state solutions is attained with a diagonalized approximate factorization (AF) algorithm. Results are presented for Riemann's problem, for a regular shock reflection at an inviscid wall, for supersonic flow past a cylinder, and for a transonic airfoil. All computed shocks are ideally sharp and in excellent agreement with other numerical results or 'exact' solutions. Most importantly, this has been accomplished on unusually crude meshes without any attempt to align grid lines with shock fronts or to cluster grid lines around shocks.

Hartwich, PETER-M.

1990-01-01

268

Design and evaluation of hydrophobic coated buoyant core as floating drug delivery system for sustained release of cisapride  

PubMed Central

An inert hydrophobic buoyant coated–core was developed as floating drug delivery system (FDDS) for sustained release of cisapride using direct compression technology. Core contained low density, porous ethyl cellulose, which was coated with an impermeable, insoluble hydrophobic coating polymer such as rosin. It was further seal coated with low viscosity hydroxypropyl methyl cellulose (HPMC E15) to minimize moisture permeation and better adhesion with an outer drug layer. It was found that stable buoyant core was sufficient to float the tablet more than 8 h without the aid of sodium bicarbonate and citric acid. Sustained release of cisapride was achieved with HPMC K4M in the outer drug layer. The floating lag time required for these novel FDDS was found to be zero, however it is likely that the porosity or density of the core is critical for floatability of these tablets. The in vitro release pattern of these tablets in simulated gastric fluid showed the constant and controlled release for prolonged time. It can be concluded that the hydrophobic coated buoyant core could be used as FDDS for gastroretentive delivery system of cisapride or other suitable drugs.

Jacob, Shery; Nair, Anroop B; Patil, Pandurang N

2010-01-01

269

Floating, surface liquids retrieval system  

SciTech Connect

A floating retriever is disclosed for retrieving, for example, spilled oil or other liquid substances on the top of water having a central liquid collection chamber with a vacuum or suction pick-up for delivery of the pollutants to, for example, a mother vessel which controls the retriever by means of, for example, a boom structure. The retriever has a large surrounding circular float with intake ports with rotational, wiper/configured, laterally disposed vaned cylinders to bring the retrieved liquid to the collection chamber. The device includes an inverted-dome, variable level, water well for stability, as well as radially positioned, selectively controlled, out-rigger, floating screws which may turn clockwise or counter-clockwise for both drawing the oil to the intake ports and providing for propulsion and guidance. In an alternate embodiment, an initial, gravity oil/water separator is included in the retriever in association with the central collection chamber.

Gordon, E.T.

1983-07-05

270

Acetaminophen-containing chewable tablets with suppressed bitterness and improved oral feeling.  

PubMed

The aim of this study was to develop acetaminophen chewable tablets with suppressed bitterness and improved oral feeling by examination of hard fats as the matrix base and of sweetening agents as corrigents. Witepsol H-15, W-35, S-55, E-75 and E-85, and Witocan H and 42/44 were used as hard fats. Witocan H and 42/44 were selected in view of improved oral feeling. Witocan H/Witocan 42/44 mixture tablets showed different melting characteristics and drug release rates dependent on their ratios, and those with the Witocan H/Witocan 42/44 ratio of 92.5% (w/w) and more showed good drug release. Sucrose, xylitol, saccharin, saccharin sodium, aspartame and sucralose were used as sweetening agents, and applied alone or with Benecoat BMI-40 or cocoa powder. The Witocan H tablet with 1% (w/w) saccharin plus 5% (w/w) Benecoat BMI-40 (Sc1-B5), and the Witocan H/Witocan 42/44 (92.5:7.5, w/w) mixture tablet with 1% (w/w) aspartame plus 5% (w/w) Benecoat BMI-40 suppressed bitterness and sweetness excellently, but the former tablet showed better drug release. Thus, the Witocan H tablet with Sc1-B5 is suggested as the best acetaminophen chewable tablet, exhibiting suppressed bitterness, low sweetness, improved oral feeling and good drug release. PMID:15158948

Suzuki, Hiroyuki; Onishi, Hiraku; Hisamatsu, Seiji; Masuda, Kosuke; Takahashi, Yuri; Iwata, Masanori; Machida, Yoshiharu

2004-06-18

271

Why Do Countries Float the Way They Float?  

Microsoft Academic Search

Countries that are classified as having floating exchange rate systems (or very wide bands) show strikingly different patterns of behavior. They hold very different levels of international reserves and allow very different volatilities in the movements of the exchange rate relative to the volatility that they tolerate either on the level of reserves or in interest rates. We document these

Ricardo Hausmann; Ugo G. Panizza; Ernesto Hugo Stein

2000-01-01

272

Why do countries float the way they float?  

Microsoft Academic Search

Countries that are classified as having floating exchange rate systems (or very wide bands) show strikingly different patterns of behavior. They hold very different levels of international reserves and allow very different volatilities to the movements of the exchange rate relative to the volatility that they tolerate either on the level of reserves or on interest rates. We document these

Ricardo Hausmann; Ugo Panizza; Ernesto Stein

2001-01-01

273

Strength tests on hulls and floats  

NASA Technical Reports Server (NTRS)

The present report deals with strength tests on hulls and floats intended in part for the collection of construction data for the design of these components and in part for the stress analysis of the finished hulls and floats.

Matthaes, K

1942-01-01

274

Dynamics of a Floating Ice Sheet.  

National Technical Information Service (NTIS)

Civilian and military operations are frequently conducted on the surface of floating ice sheets. For reasons of safety and operational reliability it is often required to predict the deformation and stresses in such floating ice plates due to surface load...

H. Reismann Y. C. Lee

1968-01-01

275

Modeling International Space Station (ISS) Floating Potentials.  

National Technical Information Service (NTIS)

The floating potential of the International Space Station (ISS) as a function of the electron current collection of its high voltage solar array panels is derived analytically. Based on Floating Potential Probe (FPP) measurements of the ISS potential and ...

D. C. Ferguson B. Gardner

2002-01-01

276

E-Books and the Tablet PC.  

ERIC Educational Resources Information Center

Highlights the emerging technologies of e-books, electronic versions of texts, and the Tablet PC, a new hybrid laptop computer and personal digital assistant that features a writing tablet and stylus-based input/navigation. (Author/VWL)

Goodwin-Jones, Bob

2003-01-01

277

21 CFR 520.1310 - Marbofloxacin tablets.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Marbofloxacin tablets. 520.1310 Section 520...FORM NEW ANIMAL DRUGS § 520.1310 Marbofloxacin tablets. (a) Specifications ...50, 100, or 200 milligrams (mg) marbofloxacin. (b) Sponsor. See No....

2009-04-01

278

21 CFR 520.1310 - Marbofloxacin tablets.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Marbofloxacin tablets. 520.1310 Section 520...FORM NEW ANIMAL DRUGS § 520.1310 Marbofloxacin tablets. (a) Specifications ...50, 100, or 200 milligrams (mg) marbofloxacin. (b) Sponsor. See No....

2010-04-01

279

21 CFR 520.1380 - Methocarbamol tablets.  

Code of Federal Regulations, 2013 CFR

...DRUGS § 520.1380 Methocarbamol tablets. (a) Chemical name. 3-(O-Methoxyphenoxy)-1,2-propanediol 1-carbamate. (b) Specifications. Each tablet contains 500 milligrams of methocarbamol. (c) Sponsor. See No. 000856...

2013-04-01

280

[Technology and analysis of "Askoeziuofito" tablets].  

PubMed

The objective of this work is to produce chewable tablets out of Echinacea purpurea liquid extract (1:1) and ascorbic acid: to create the technology, to select methods of analysis and to examine stability. The paper describes the technology of tablets: a method of condensation is chosen; the influence of additional substances over tableting is established; pressing characteristics of tableting mixtures are examined. The quality of tablets is evaluated in terms of appearance and technological rates: average tablet mass, hardness against pressure, hardness against wearing, time of disintegration, and speed of ascorbic acid secretion. The identity of ascorbic acid, ferments and hydroxycinamon acid was established. Quantities of ascorbic and chicory acids were defined. The tablets produced were named "Askoeziuofito" tablets. The name consists of abbreviated terms of ascorbic acid, Echinacea plant and phytochemical preparation. PMID:14617854

Bernatoniene, Jurga; Savickiene, Nijole; Savickas, Ar?nas; Bernatonis, Domininkas

2003-01-01

281

40 CFR 65.45 - External floating roof converted into an internal floating roof.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false External floating roof converted into an internal floating roof. 65.45 Section 65.45 Protection...RULE Storage Vessels § 65.45 External floating roof converted into an internal floating...

2013-07-01

282

Galileo's Telescopy and Jupiter's Tablet  

NASA Astrophysics Data System (ADS)

A previous paper (BAAS 33:4, 1363, 2001) reported on the dramatic scene in Shakespeare's Cymbeline that features the descent of the deity Jupiter. The paper suggested that the four ghosts circling the sleeping Posthumus denote the four Galilean moons of Jupiter. The god Jupiter commands the ghosts to lay a tablet upon the prone Posthumus, but says that its value should not be overestimated. When Posthumus wakens he notices the tablet, which he calls a "book." Not only has the deity's "tablet" become the earthling's "book," but it appears that the book has covers which Posthumus evidently recognizes because without even opening the book he ascribes two further properties to it: rarity, and the very property that Jupiter had earlier attributed, viz. that one must not read too much into it. The mystery deepens when the Jovian gift undergoes a second metamorphosis, to "label." With the help of the OED, the potentially disparate terms "tablet," "book," and "label," may be explained by terms appropriate either to supernatural or worldly beings. "Tablet" may recognize the Mosaic artifact, whereas "book" and "label" are probably mundane references to Galileo's Sidereus Nuncius which appeared shortly before Cymbeline. The message of the Olympian god indicates therefore that the book is unique even as its contents have limited value. The first property celebrates the fact that Galileo's book is the first of its kind, and the second advises that all results except the discovery of Jupiter's moons have been reported earlier, in Hamlet.

Usher, P. D.

2003-12-01

283

32 CFR 935.165 - Floating objects.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Floating objects. 935.165 Section 935...CODE Public Safety § 935.165 Floating objects. No person may anchor, moor, or beach any boat, barge, or other floating object on Wake Island in any location...

2013-07-01

284

Floating, surface liquids retrieval system  

Microsoft Academic Search

A floating retriever is disclosed for retrieving, for example, spilled oil or other liquid substances on the top of water having a central liquid collection chamber with a vacuum or suction pick-up for delivery of the pollutants to, for example, a mother vessel which controls the retriever by means of, for example, a boom structure. The retriever has a large

1983-01-01

285

Suminagashi: Floating Ink Paper Marbling  

NSDL National Science Digital Library

In this activity, learners try to float ink on the surface of water to create a pattern and then capture it with absorbent paper. This technique, called Suminagashi, is an ancient Japanese style of decorating paper with inks and believed to be the oldest form of marbling. This art activity can introduce learners to fluid mechanics, viscosity, and surface tension.

Henricks, Jessica

2012-06-26

286

Floating-roof tank evaporation  

SciTech Connect

The book describes an improved method for estimating the total evaporative losses of the equivalent atmospheric hydrocarbon emissions from external floating-roof tanks that contain multicomponent hydrocarbon mixtures (such as gasolines and crude oils) or single-component stocks (such as petro-chemicals).

Not Available

1989-01-01

287

Floating support for older people  

Microsoft Academic Search

The introduction of ‘floating support’ - a tenure neutral service - in many local authorities is causing much consternation among tenants because the scheme manager they thought would always be there is leaving. Yet, with an ageing population combined with increasingly finite resources, how can services provide support to those who need it most and to what degree should sheltered

Tony Cousins; Phil Saunders

2008-01-01

288

Float It Down the River.  

ERIC Educational Resources Information Center

Presents an activity that involves students in a hands-on, creative project in which they use higher order thinking skills while designing and studying the basics of floating devices. Focuses on inquiry, a number of scientific principles, and the relationship between mathematics and science. (ASK)

Brendzel, Sharon; Orfan, Lucy; Schuhmacher, Robert

2000-01-01

289

Floating Ring-Groove Lapper  

NASA Technical Reports Server (NTRS)

Tool fits out-of-round seal groove and laps it to fine finish without binding. Includes floating lapping pieces riding freely in groove, and are curved to match nominal diameter of groove. One lapping piece tightened so it does not move relative to disk.

Williams, Robert L., Sr.; Williams, Robert L., Jr.; Chase, Timothy L.

1992-01-01

290

Float It Down the River  

NSDL National Science Digital Library

Float it Down the River is an exciting design activity that involves students in a hands-on, creative project in which they use higher order thinking skills in a motivating setting. Students working in groups of four to six are challenged to design and bu

Orfan, Lucy; Schuhmacher, Robert; Brendzel, Sharon

2000-10-01

291

Mathematical Modeling of Floating Ice  

NASA Astrophysics Data System (ADS)

A significant fraction of the surface of the global ocean is covered by floating ice, the presence of which has profound influences on the state of the global climate system. The floating ice appears both in the form of sea-ice, created in situ over the open ocean, and in the form of ice shelves, the result of land ice sheets draining into the ocean. Ice is arguably one of the most complex fluids in the climate system, both from a dynamical and thermodynamical point of view. The former because of its inherently non-linear rheology and the later because of the ice-albedo feedback mechanism. Added to these complexities, the mathematical and computational modeling of floating has the pragmatic difficulty of properly treating phenomena that occur both on sub-grid scales and disparate time scales. Examples of sub-grid scale phenomena include the treatment of sea-ice thickness distributions and the effects of ocean geostrophic turbulence on the sea ice. This talk presents an overview of the role of floating ice in the climate system, some of the outstanding theoretical challenges, and the role in which modern applied mathematics may play in the future development of the field.

Holland, D. M.

2001-05-01

292

Airship-floated wind turbine  

Microsoft Academic Search

A wind turbine, by use of a tethered airship for support, may be designed for the economical recovery of power at heights of 2,000 feet or more above ground, at which height power density in the wind is typically three times the power density available to a conventionally supported wind turbine. Means can be added to such an airship-floated wind

1985-01-01

293

Topographic Characterization of Cellulose Bilayered Tablets Interfaces  

Microsoft Academic Search

The introduction of bilayer tablets into the pharmaceutical industry has enabled the development of pre-determined release profiles of active ingredients. During production, however, these bilayer tablets have the tendency to fracture by capping, thought to be caused by internal tensile stresses normal to the plane of fracture. Bi-layered tablets of the widely used excipient microcrystalline cellulose (MCC) have been manufactured

S. J. Inman; B. J. Briscoe; K. G. Pitt

2007-01-01

294

Mathematics Instruction and the Tablet PC  

ERIC Educational Resources Information Center

The use of tablet PCs in teaching is a relatively new phenomenon. A cross between a notebook computer and a personal digital assistant (PDA), the tablet PC has all of the features of a notebook with the additional capability that the screen can also be used for input. Tablet PCs are usually equipped with a stylus that allows the user to write on…

Fister, K. Renee; McCarthy, Maeve L.

2008-01-01

295

Tablet - next generation sequence assembly visualization  

Microsoft Academic Search

Summary: Tablet is a lightweight, high-performance graphical viewer for next generation sequence assemblies and alignments. Supporting a range of input assembly formats, Tablet provides high- quality visualizations showing data in packed or stacked views, al- lowing instant access and navigation to any region of interest, and whole contig overviews and data summaries. Tablet is both multi- core aware and memory-efficient,

Iain Milne; Micha Bayer; Linda Cardle; Paul Shaw; Gordon Stephen; Frank Wright; David Marshall

2010-01-01

296

Scaffolding Equals Success in Teaching Tablet PCs  

ERIC Educational Resources Information Center

After many years of using the mouse and keyboard as the primary means of computer input, people are seeing a strong surge into a new generation of input technologies such as tablet PCs. As more professionals adopt tablet PCs for use in the workplace, there is a subsequent increased demand for tablet PC instruction in the classroom. Examples of…

Dickerson, Jeremy; Williams, Scott; Browning, J. B.

2009-01-01

297

Fast Dissolving Tablets of Aloe Vera Gel  

Microsoft Academic Search

Purpose : The objective of this work was to prepare and evaluate fast dissolving tablets of the nutraceutical, freeze dried Aloe vera gel. Methods: Fast dissolving tablets of the nutraceutical, freeze-dried Aloe vera gel, were prepared by dry granulation method. The tablets were evaluated for crushing strength, disintegration time, wetting time, friability, drug content and drug release. A 3 2

Jyotsana Madan; AK Sharma; Ramnik Singh

298

Guidance for Industry Orally Disintegrating Tablets.  

National Technical Information Service (NTIS)

This guidance provides pharmaceutical manufacturers of new and generic drug products with an Agency perspective on the definition of an orally disintegrating tablet (ODT)which is a different dosage form than, for example, a chewable tablet or a tablet tha...

2008-01-01

299

Preparation and in-vivo pharmacokinetic study of a novel extended release compression coated tablets of fenoterol hydrobromide.  

PubMed

The aim of this study was to formulate extended release compression coated core tablets of fenoterol hydrobromide, a selective beta(2) adrenergic receptor agonist, in an attempt to prevent nocturnal asthma. Two hydrophilic polymers viz Kollidon SR, Polyox WSR 303 and a hydrophobic one (Precirol ATO5) were employed. Compression coated tablets were formulated by preparing a core tablet containing 7.5 mg drug and various amounts of polymer and Emcompress then compressed coated with the same polymeric materials. For comparison purpose different matrix tablets were also prepared employing the same polymers. In-vitro release studies were carried out at different pH (1.2 and 6.8). Pharmacokinetics of extended release tablets as well as commercially available immediate release tablets (Berotec) were studied after oral administration to beagle dogs using a new developed LC-MS/MS method with a lower limit of quantification of 1 ng/ml. Fenoterol release from compression coated tablets was significantly lower than matrix tablets. The mechanism of release was changed with the nature and content of polymer. The release pattern of drug from F16 containing 40 mg Kollidon SR divided in the core tablet (15 mg) and the rest in the compressed coat (25 mg) showed a typical zero order release kinetic that could extend drug release >10 h and reasonable time for 75% to be released (t(75)) (8.92 h). When compared to immediate release Berotec tablet the MRT was significantly extended from 7.03 +/- 0.76 to 10.93 +/- 1.25 h (P < 0.001) and HVD(t 50%Cmax) was also significantly extended from 2.71 +/- 0.68 to 6.81 +/- 0.67 h with expected prevention of nocturnal asthma. PMID:18770048

Elshafeey, Ahmed H; Sami, Elshaimaa I

2008-01-01

300

Preparation and In-vivo Pharmacokinetic Study of a Novel Extended Release Compression Coated Tablets of Fenoterol Hydrobromide  

PubMed Central

The aim of this study was to formulate extended release compression coated core tablets of fenoterol hydrobromide, a selective ?2 adrenergic receptor agonist, in an attempt to prevent nocturnal asthma. Two hydrophilic polymers viz Kollidon® SR, Polyox® WSR 303 and a hydrophobic one (Precirol® ATO5) were employed. Compression coated tablets were formulated by preparing a core tablet containing 7.5 mg drug and various amounts of polymer and Emcompress® then compressed coated with the same polymeric materials. For comparison purpose different matrix tablets were also prepared employing the same polymers. In-vitro release studies were carried out at different pH (1.2 and 6.8). Pharmacokinetics of extended release tablets as well as commercially available immediate release tablets (Berotec®) were studied after oral administration to beagle dogs using a new developed LC-MS/MS method with a lower limit of quantification of 1 ng/ml. Fenoterol release from compression coated tablets was significantly lower than matrix tablets. The mechanism of release was changed with the nature and content of polymer. The release pattern of drug from F16 containing 40 mg Kollidon® SR divided in the core tablet (15 mg) and the rest in the compressed coat (25 mg) showed a typical zero order release kinetic that could extend drug release >10 h and reasonable time for 75% to be released (t75) (8.92 h). When compared to immediate release Berotec® tablet the MRT was significantly extended from 7.03?±?0.76 to 10.93?±?1.25 h (P?

Sami, Elshaimaa I.

2008-01-01

301

Calcium phosphates in pharmaceutical tableting. 2. Comparison of tableting properties.  

PubMed

Ten calcium phosphates suitable for direct compression (dibasic calcium phosphate dihydrate, dibasic calcium phosphate anhydrous and hydroxylapatite) were investigated with respect to their compressional behaviour. Except for Di-Cafos A all products gave tablets with sufficient to good mechanical strength. Nevertheless, there were differences between the products. All tablets prepared from the different products showed a high friability. This seems to be a problem of the calcium phosphates in general. On the other hand, the influence of magnesium stearate on the mechanical strength of the tablets was negligible for all products investigated. Moreover, a considerable effect of the particle size on the tensile strength of the tablets was found. The ejection forces and residual pressures were high in general, but critical only in the case of hydroxylapatites. Heckel plots were used to differentiate between plastic deformation and brittle fracture of the particles. In the case of calcium phosphates the slope of the Heckel plots indicated the hardness of the particles rather than their deformation behaviour. PMID:8348107

Schmidt, P C; Herzog, R

1993-06-18

302

Silicone adhesive matrix of verapamil hydrochloride to provide pH-independent sustained release.  

PubMed

Providing pH-independent oral release of weakly basic drugs with conventional matrix tablets can be challenging because of the pH-dependent solubility characteristics of the drugs and the changing pH environment along the gastrointestinal tract. The aim of the present study was to use a hydrophobic polymer to overcome the issue of pH-dependent release of weakly basic model drug verapamil hydrochloride from matrix tablets without the use of organic buffers in the matrix formulations. Silicone pressure-sensitive adhesive (PSA) polymer was evaluated because of its unique properties of low surface energy, hydrophobicity, low glass transition temperature, high electrical resistance, and barrier to hydrogen ion diffusion. Drug release, hydrogen ion diffusion, tablet contact angle, and internal tablet microenvironment pH with matrix tablets prepared using PSA were compared with those using water-insoluble ethyl cellulose (EC). Silicone PSA films showed higher resistance to hydrogen ion diffusion compared with EC films. Verapamil hydrochloride tablets prepared using silicone PSA showed higher hydrophobicity and lower water uptake than EC tablets. Silicone PSA tablets also showed pH-independent release of verapamil and decreased in dimensions during drug dissolution. By contrast, verapamil hydrochloride tablets prepared using EC did not achieve pH-independent release. PMID:24022347

Tolia, Gaurav; Li, S Kevin

2014-02-01

303

The strength of bilayered tablets  

Microsoft Academic Search

The tensile strength of model materials (dicalcium phosphate dihydrate, microcrystalline cellulose and pregelatinised starch) compacted to form tablets in the form of beams consisting of two layers of equal thickness has been determined by three-point loading. The values of the tensile strength of the materials were sometimes higher and sometimes lower than the tensile strength of beams of the same

F. Podczeck; K. R. Drake; J. M. Newton; I. Haririan

2006-01-01

304

Accelerating Microblaze Floating Point Operations  

Microsoft Academic Search

The MicroBlaze processor serves in many FPGA designs as the central 32 bit CPU with access to the global off chip memory and peripherals. MicroBlaze provides FSL links for up to 8 coprocessors. We present two MicroBlaze designs. The first design works with 8 PicoBlaze-based accelerators for pipelined, single-precision floating point vector-oriented operations, and delivers over 1.2 GFLOPs. The second

Jiri Kadlec; Roman Bartosinski; Martin Danek

2007-01-01

305

Decimal Floating-Point Multiplication  

Microsoft Academic Search

Decimal multiplication is important in many com- mercial applications including financial analysis, banking, tax calculation, currency conversion, insurance, and accounting. This paper presents the design of two decimal floating-point multipli- ers; one whose partial product accumulation strategy employs decimal carry-save addition, and one which employs binary carry-save addition. The multiplier based on decimal carry- save addition favors a non-pipelined, iterative

Mark A. Erle; Brian J. Hickmann; Michael J. Schulte

2009-01-01

306

Profiling of ecstasy tablets seized in iran.  

PubMed

In this study 50 samples of ecstasy tablets seized in Iran during the period of 2007 through 2008 were examined and their physical characteristics (appearance, marking, scored/not scored, color, weight, diameter, thickness) were determined. In order to determine the chemical characteristics of these tablets, color tests (Marquis test, Simon's test, Chen's test and Gallic acid test), Thin Layer Chromatography (TLC), anion test, residual solvents, Gas Chromatography-Mass Spectrometry (GC-MS) and Liquid Chromatography-Mass Spectrometry (LC-MS) were carried out on the tablets. The range of tablets weight was 96-308 mg and the range of 3,4-methylenedioxymethamphetamine (MDMA) hydrochloride content in these tablets was 60-180 mg. No good correlation was found between the tablets weight and their MDMA contents. All of the tablets containing MDMA had this compound in hydrochloride form. Ketamine, phenmetrazine and ephedrine (or pseudoephedrine) were found in some of the tablets along with MDMA. No MDMA was found in 20% of the tablets. Some of these tablets contained compounds such as caffeine or tramadol as their active ingredient. PMID:24250345

Khajeamiri, Ali Reza; Kobarfard, Farzad; Ahmadkhaniha, Reza; Mostashari, Gelareh

2011-01-01

307

Profiling of Ecstasy Tablets Seized in Iran  

PubMed Central

In this study 50 samples of ecstasy tablets seized in Iran during the period of 2007 through 2008 were examined and their physical characteristics (appearance, marking, scored/not scored, color, weight, diameter, thickness) were determined. In order to determine the chemical characteristics of these tablets, color tests (Marquis test, Simon’s test, Chen’s test and Gallic acid test), Thin Layer Chromatography (TLC), anion test, residual solvents, Gas Chromatography-Mass Spectrometry (GC-MS) and Liquid Chromatography-Mass Spectrometry (LC-MS) were carried out on the tablets. The range of tablets weight was 96–308 mg and the range of 3,4-methylenedioxymethamphetamine (MDMA) hydrochloride content in these tablets was 60–180 mg. No good correlation was found between the tablets weight and their MDMA contents. All of the tablets containing MDMA had this compound in hydrochloride form. Ketamine, phenmetrazine and ephedrine (or pseudoephedrine) were found in some of the tablets along with MDMA. No MDMA was found in 20% of the tablets. Some of these tablets contained compounds such as caffeine or tramadol as their active ingredient.

Khajeamiri, Ali Reza; Kobarfard, Farzad; Ahmadkhaniha, Reza; Mostashari, Gelareh

2011-01-01

308

Tank Tests of Twin Seaplane Floats  

NASA Technical Reports Server (NTRS)

The following report contains the most essential data for the hydrodynamic portion of the twin-float problem. The following points were successfully investigated: 1) difference between stationary and nonstationary flow; 2) effect of the shape of the step; 3) effect of distance between floats; 4) effect of nose-heavy and tail-heavy moments; 5) effect of the shape of floats; 6) maneuverability.

Herrman, H; Kempf, G; Kloess, H

1928-01-01

309

Interaction between fed gastric media (Ensure Plus®) and different hypromellose based caffeine controlled release tablets: comparison and mechanistic study of caffeine release in fed and fasted media versus water using the USP dissolution apparatus 3.  

PubMed

The aim of the study was to investigate caffeine release in fed and fasted state media from three controlled release matrix tablets containing different HPMC viscosity grades. The biorelevant in vitro dissolution methods utilize the USP 3 dissolution apparatus and biorelevant media to simulate fed and fasted gastro-intestinal dissolution conditions. The effect of tablet reciprocation rate (dip speed) in dissolution media (10 and 15 dips per minute) and media (water, fed and fasted) on caffeine release rate from - and erosion rate of - 100, 4000 and 15,000 mPa s HPMC viscosity tablets was investigated using factorial designed experiments. Furthermore, the mechanism of release in Ensure Plus(®), a nutrition drink similar in composition to the FDA standard meal, was investigated by studying tablet swelling using texture analysis. Altering dip speed has negligible effect on release and erosion rates. Using fasted media instead of water slightly decreases caffeine release from 100 and 4000 mPa s HPMC viscosity tablets as well as erosion rates, while 15,000 mPa s tablets remain unaffected. Fed compared to fasted media decreases caffeine release rate, and the food effect is greater for the 100 mPa s viscosity tablets compared to the 4000 and 15,000 mPa s viscosity tablets. The investigation using texture analysis indicates that Ensure Plus(®) becomes rate-limiting for caffeine release from HPMC tablets by forming a hydrophobic barrier around the tablets. The barrier decreases tablet water permeation, which decreases erosion rate in 100 mPa s viscosity tablets, swelling in 15,000 mPa s viscosity tablets and caffeine release from both tablets. This observed interaction between Ensure Plus(®) and the HPMC tablets may translate into decreased drug release rate in the fed stomach, which may decrease the amount of drug available for absorption in the small intestine and thus reduce systemic drug exposure and maximum plasma concentration. PMID:24342711

Franek, Frans; Holm, Per; Larsen, Frank; Steffansen, Bente

2014-01-30

310

Modeling International Space Station (ISS) Floating Potentials  

NASA Technical Reports Server (NTRS)

The floating potential of the International Space Station (ISS) as a function of the electron current collection of its high voltage solar array panels is derived analytically. Based on Floating Potential Probe (FPP) measurements of the ISS potential and ambient plasma characteristics, it is shown that the ISS floating potential is a strong function of the electron temperature of the surrounding plasma. While the ISS floating potential has so far not attained the pre-flight predicted highly negative values, it is shown that for future mission builds, ISS must continue to provide two-fault tolerant arc-hazard protection for astronauts on EVA.

Ferguson, Dale C.; Gardner, Barbara

2002-01-01

311

21 CFR 520.1242e - Levamisole hydrochloride effervescent tablets.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Levamisole hydrochloride effervescent tablets...FORM NEW ANIMAL DRUGS § 520.1242e Levamisole hydrochloride effervescent tablets...Each tablet contains 907 milligrams of levamisole hydrochloride. (b) Sponsor....

2010-04-01

312

21 CFR 520.2041 - Pyrantel pamoate chewable tablets.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Pyrantel pamoate chewable tablets. 520.2041 Section 520.2041 Food and Drugs...NEW ANIMAL DRUGS § 520.2041 Pyrantel pamoate chewable tablets. (a) Specifications. Each tablet...

2010-04-01

313

21 CFR 520.2150b - Stanozolol chewable tablets.  

Code of Federal Regulations, 2010 CFR

... 2009-04-01 false Stanozolol chewable tablets. 520.2150b Section 520.2150b...ANIMAL DRUGS § 520.2150b Stanozolol chewable tablets. (a) Specifications. Each chewable tablet contains 2 milligrams of...

2009-04-01

314

21 CFR 520.2150b - Stanozolol chewable tablets.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Stanozolol chewable tablets. 520.2150b Section 520.2150b...ANIMAL DRUGS § 520.2150b Stanozolol chewable tablets. (a) Specifications. Each chewable tablet contains 2 milligrams of...

2010-04-01

315

Floating Ice-Algal Aggregates below Melting Arctic Sea Ice  

PubMed Central

During two consecutive cruises to the Eastern Central Arctic in late summer 2012, we observed floating algal aggregates in the melt-water layer below and between melting ice floes of first-year pack ice. The macroscopic (1-15 cm in diameter) aggregates had a mucous consistency and were dominated by typical ice-associated pennate diatoms embedded within the mucous matrix. Aggregates maintained buoyancy and accumulated just above a strong pycnocline that separated meltwater and seawater layers. We were able, for the first time, to obtain quantitative abundance and biomass estimates of these aggregates. Although their biomass and production on a square metre basis was small compared to ice-algal blooms, the floating ice-algal aggregates supported high levels of biological activity on the scale of the individual aggregate. In addition they constituted a food source for the ice-associated fauna as revealed by pigments indicative of zooplankton grazing, high abundance of naked ciliates, and ice amphipods associated with them. During the Arctic melt season, these floating aggregates likely play an important ecological role in an otherwise impoverished near-surface sea ice environment. Our findings provide important observations and measurements of a unique aggregate-based habitat during the 2012 record sea ice minimum year.

Assmy, Philipp; Ehn, Jens K.; Fernandez-Mendez, Mar; Hop, Haakon; Katlein, Christian; Sundfjord, Arild; Bluhm, Katrin; Daase, Malin; Engel, Anja; Fransson, Agneta; Granskog, Mats A.; Hudson, Stephen R.; Kristiansen, Svein; Nicolaus, Marcel; Peeken, Ilka; Renner, Angelika H. H.; Spreen, Gunnar; Tatarek, Agnieszka; Wiktor, Jozef

2013-01-01

316

Bioequivalence study of nabumetone tablets in man  

Microsoft Academic Search

A nabumetone tablet in development (NabutonR) was tested for its bioequivalence to the reference tablet (UnitonR). Seventeen healthy Korean male subjects participated in this study. Each subject received a 1-g dose of nabumetone (2 tablets\\u000a each) in an unbalanced, randomized, two-way crossover investigation. Serum concentrations of 6-methoxy-2-naphthylacetic acid\\u000a (6-MNA), a major metabolite of nabumetone, were measured over 120 hr interval

Young-Joo Lee; Eun-Ju Jang; Jeong-Uk Lee; Yong-Hae Han; Suk-Jae Chung; Min-Hwa Lee; Chang-Koo Shim

1995-01-01

317

Condition and Error Estimates in Numerical Matrix Computations  

SciTech Connect

This tutorial paper deals with sensitivity and error estimates in matrix computational processes. The main factors determining the accuracy of the result computed in floating--point machine arithmetics are considered. Special attention is paid to the perturbation analysis of matrix algebraic equations and unitary matrix decompositions.

Konstantinov, M. M. [University of Architecture, Civil Engineering and Geodesy, 1046 Sofia (Bulgaria); Petkov, P. H. [Technical University of Sofia, 1000 Sofia (Bulgaria)

2008-10-30

318

Wave drag on floating bodies  

PubMed Central

We measure the deceleration of liquid nitrogen drops floating at the surface of a liquid bath. On water, the friction force is found to be about 10 to 100 times larger than on a solid substrate, which is shown to arise from wave resistance. We investigate the influence of the bath viscosity and show that the dissipation decreases as the viscosity is increased, owing to wave damping. The measured resistance is well predicted by a model imposing a vertical force (i.e., the drop weight) on a finite area, as long as the wake can be considered stationary.

Le Merrer, Marie; Clanet, Christophe; Quere, David; Raphael, Elie; Chevy, Frederic

2011-01-01

319

Mucoadhesive tablets for controlled release of acyclovir.  

PubMed

Mucoadhesive chitosan (CS) and/or hydroxypropyl-methylcellulose (HPMC) tablets for gastric drug delivery of acyclovir (ACV) have been developed in order to improve the ACV oral bioavailability. Swelling, bioadhesive and dissolution studies were carried out in two acidic media (pH 1.5 and 4) in order to determine the tablets behaviour in both fed and fasted states. All the designed tablets showed good mucoadhesive properties on gastric mucosa due to the presence of CS and/or HPMC. In vitro dissolution of ACV from tablets was influenced by the swelling behaviour of each polymer. All data release of the studied tablets fitted to Hopfenberg model, which describes drug release from tablets displaying heterogeneous erosion. HPMC and CS/HPMC tablets revealed a sustained release for 24 h, but a complete dissolution of the tablets was not produced at this time. On the contrary, tablets which contained only CS as polymer were able to release the total amount of ACV for 4 h, due to the CS imbibition and erosion processes in pH 1.5 medium. These results allowed us to conclude that CS is the excipient to be chosen to obtain gastroretentive formulations, due to its demonstrated gastric compatibility. PMID:22863800

Ruiz-Caro, Roberto; Gago-Guillan, Manuel; Otero-Espinar, Francisco Javier; Veiga, María Dolores

2012-01-01

320

33 CFR 143.120 - Floating OCS facilities.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Floating OCS facilities. 143.120 Section...EQUIPMENT OCS Facilities § 143.120 Floating OCS facilities. (a) Before construction is started on a proposed floating OCS facility, the owner...

2013-07-01

321

Formulation and optimization of mucoadhesive bilayer buccal tablets of atenolol using simplex design method  

PubMed Central

Introduction: In the present study, mucoadhesive buccal bilayer tablets of atenolol were fabricated with the objective of avoiding first pass metabolism and to improve its bioavailability with reduction in dosing frequency. Hence, the aim of this work was to design oral controlled release mucoadhesive tablets of atenolol and to optimize the drug release profile and bioadhesion. Materials and Methods: Bilayer buccal tablets of atenolol were prepared by direct compression method using simplex method of optimization to investigate the combined effect of hydroxypropyl methylcellulose 15 cps (X1), Carbopol (X2) and mannitol (X3); the in vitro drug release (Y1) and mucoadhesive strength (Y2) were taken as responses. The designed tablets were evaluated for various physical and biological parameters like drug content uniformity, in vitro drug release, short-term stability, and drug- excipient interactions (FTIR). Results: The formulation C containing hydroxypropyl methylcellulose 15 cps (10% w/w of matrix layer), Carbopol 934p (10% w/w of matrix layer) and mannitol (channeling agent, 40% w/w of matrix layer) was found to be promising. This formulation exhibited an in vitro drug release of 89.43% in 9 h along with satisfactory bioadhesion strength (7.20 g). Short-term stability studies on the promising formulation indicated that there are no significant changes in drug content and in vitro dissolution characteristics (P<0.05). IR spectroscopic studies indicated that there are no drug-excipient interactions.

Shirsand, SB; Suresh, Sarasija; Keshavshetti, GG; Swamy, PV; Reddy, P Vijay Prakash

2012-01-01

322

Wax scraper for floating roof tanks  

Microsoft Academic Search

A wax scraper is described for removing waxy deposits from the inside surface of floating roof storage tanks during the operation of such tanks, without requiring the removal of all obstructions from the inside surface of the tanks. The floating roof structure has affixed to it a number of support means. Each support means carries a scraper blade having scraper

H. A. Maeder; A. H. Nelson; F. R. Neely

1971-01-01

323

Customers' perceptions of floating restaurants in Egypt  

Microsoft Academic Search

Floating restaurants are a new phenomenon for dining out in Cairo, where customers can be provided not only with a meal but also an entertaining casual dining experience with unrivalled views of the Nile River. This study aims to identify customers perceptions of the floating restaurants sailing down the Nile River and also explores the different attributes that influence customer

Hany H. S. Abdelhamied

2011-01-01

324

Heaving response of a large floating platform  

Microsoft Academic Search

In this paper, we tackle a new dynamic problem of a large floating platform in a heaving harmonic motion due to 9000 performers or people simultaneously jumping in mass events. The objective is to estimate the heaving response of the floating structure so as to establish whether the participants will be at ease during their performances. By assuming the platform

C. M. Wang; T. Utsunomiya; H. S. Koh

2008-01-01

325

DRILL VESSELS FLOAT IN AERATED WATER  

Microsoft Academic Search

Model tests, calculations, and case studies prove that a floating vessel will not sink due to gas reducing the water density in or adjacent to a subsea blowout. Several floating drill vessels have been lost as a result of subsea blowouts. Reports have circulated that the rig sank into something similar to a hole in the ocean caused by gas

D. S. Hammett

1985-01-01

326

A General Equilibrium Analysis of Check Float  

Microsoft Academic Search

Households and businesses in the U.S. prefer to use checks over less costly means of payment. Earlier studies have focused on check “float” as an explanation for the continued popularity of this seemingly inefficient technology. We construct a general equilibrium model of check payment and show that the presence of float does not necessarily lead to inefficiency. However, we also

James McAndrews; William Roberds

1999-01-01

327

Algorithms for arbitrary precision floating point arithmetic  

Microsoft Academic Search

The author presents techniques for performing computations of very high accuracy using only straightforward floating-point arithmetic operations of limited precision. The validity of these techniques is proved under very general hypotheses satisfied by most implementations of floating-point arithmetic. To illustrate the applications of these techniques, an algorithm is presented which computes the intersection of a line and a line segment.

Douglas M. Priest

1991-01-01

328

Vertical pump with free floating check valve  

DOEpatents

A vertical pump with a bottom discharge having a free floating check valve isposed in the outlet plenum thereof. The free floating check valve comprises a spherical member with a hemispherical cage-like member attached thereto which is capable of allowing forward or reverse flow under appropriate conditions while preventing reverse flow under inappropriate conditions.

Lindsay, Malcolm (O'Hara Township, Allegheny County, PA)

1980-01-01

329

Whatever Floats Your Boat: A Design Challenge  

ERIC Educational Resources Information Center

This article presents a simple design challenge, based on the PBS program "Design Squad's" "Watercraft" activity that will prove engaging to most technology and engineering students. In this floating boat challenge, students are to build a boat that can float and support 25 pennies for at least 10 seconds--without leaking, sinking, or tipping…

Kornoelje, Joanne; Roman, Harry T.

2012-01-01

330

Locality in Syntax and Floating Numeral Quantifiers  

Microsoft Academic Search

We defend the idea that a floating quantifier observes syntactic locality with its associated noun phrase. This idea has given rise to a number of important empirical insights, including the VP-internal subject position, intermediate traces, and NP-traces. Recently, this syntactic locality of floating quantifiers has been questioned in a number of languages. We take up evidence from Japanese that purports

Shigeru Miyagawa; Koji Arikawa

2007-01-01

331

Floating plant dominance as a stable state  

PubMed Central

Invasion by mats of free-floating plants is among the most important threats to the functioning and biodiversity of freshwater ecosystems ranging from temperate ponds and ditches to tropical lakes. Dark, anoxic conditions under thick floating-plant cover leave little opportunity for animal or plant life, and they can have large negative impacts on fisheries and navigation in tropical lakes. Here, we demonstrate that floating-plant dominance can be a self-stabilizing ecosystem state, which may explain its notorious persistence in many situations. Our results, based on experiments, field data, and models, represent evidence for alternative domains of attraction in ecosystems. An implication of our findings is that nutrient enrichment reduces the resilience of freshwater systems against a shift to floating-plant dominance. On the other hand, our results also suggest that a single drastic harvest of floating plants can induce a permanent shift to an alternative state dominated by rooted, submerged growth forms.

Scheffer, Marten; Szabo, Sandor; Gragnani, Alessandra; van Nes, Egbert H.; Rinaldi, Sergio; Kautsky, Nils; Norberg, Jon; Roijackers, Rudi M. M.; Franken, Rob J. M.

2003-01-01

332

21 CFR 520.812 - Enrofloxacin tablets.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Enrofloxacin tablets. 520.812 Section 520...FORM NEW ANIMAL DRUGS § 520.812 Enrofloxacin tablets. (a) Specifications...68.0, or 136.0 milligrams of enrofloxacin. (b) Sponsor. See No....

2009-04-01

333

21 CFR 520.812 - Enrofloxacin tablets.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Enrofloxacin tablets. 520.812 Section 520...FORM NEW ANIMAL DRUGS § 520.812 Enrofloxacin tablets. (a) Specifications...68.0, or 136.0 milligrams of enrofloxacin. (b) Sponsor. See No....

2010-04-01

334

Tablet computers in the veterinary curriculum.  

PubMed

Tablet computers offer a new method of information management in veterinary medical education. With the tablet computer, students can annotate class notes using electronic ink, search for keywords, and convert handwriting to text as needed. Additional electronic learning resources, such as medical dictionaries and electronic textbooks, can be readily available. Eleven first-year veterinary students purchased tablet computers and participated in an investigation of their working methods and perceptions of the tablet computer as an educational tool. Most students found the technology useful. The small size and portability of the tablet allowed easy transport and use in a variety of environments. Most students adapted to electronic notetaking by the second week of classes; negative experiences with the tablet centered on a failure to become comfortable with taking notes and navigating on the computer as opposed to writing and searching on paper. A few performance-related problems, including short battery life, were reported. Tablet software allowed conversion of faculty course notes from a variety of original formats, meaning that instructors could maintain their original methods of note preparation. Adopting a consistent naming convention for files helped students to locate the files on their computers, and smaller file sizes helped with computer performance. Collaboration between students was fostered by tablet use, which offers possibilities for future development of collaborative learning environments. PMID:15834829

Eurell, Jo Ann C; Diamond, Nancy A; Buie, Brandon; Grant, David; Pijanowski, Gerald J

2005-01-01

335

21 CFR 520.1288 - Lufenuron tablets.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Lufenuron tablets. 520.1288 Section 520...FORM NEW ANIMAL DRUGS § 520.1288 Lufenuron tablets. (a) Specifications ...204.9, or 409.8 milligrams (mg) lufenuron for use as in paragraphs...

2010-04-01

336

21 CFR 520.1288 - Lufenuron tablets.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Lufenuron tablets. 520.1288 Section 520...FORM NEW ANIMAL DRUGS § 520.1288 Lufenuron tablets. (a) Specifications ...204.9, or 409.8 milligrams (mg) lufenuron for use as in paragraphs...

2009-04-01

337

Enhancing Student Performance Using Tablet Computers  

ERIC Educational Resources Information Center

Tablet PCs have the potential to change the dynamics of classroom interaction through wireless communication coupled with pen-based computing technology that is suited for analyzing and solving engineering problems. This study focuses on how tablet PCs and wireless technology can be used during classroom instruction to create an Interactive…

Enriquez, Amelito G.

2010-01-01

338

Putting Tablet PCs to the Test  

ERIC Educational Resources Information Center

Like many educators, the author and her colleagues (five faculty members and two IT techs) in the department of Media Communications and Technology at East Stroudsburg University in Pennsylvania were interested to find out the status of tablet PCs in education. Microsoft listed 10 manufacturers of tablet PCs following two forms: the slate and the…

Amirian, Susan

2004-01-01

339

Formulation and evaluation of lactoferrin bioadhesive tablets.  

PubMed

For the treatment of chronic inflammation in the oral cavity, we attempted to develop bioadhesive tablets of bovine lactoferrin (B-LF) which has antibacterial properties and immune regulatory functions. B-LF tablets containing pectin, tamarind gum or carboxymethylcellulose (CMC) were prepared by direct compression. Tablets consisting of B-LF, pectin and xylitol passed through 60- or 100-mesh sieves were also prepared. The tablets containing CMC had insufficient bioadhesive force. Although the tablets containing tamarind gum showed the longest residence time in the oral cavity, an unpleasant taste gradually developed. The tablets containing pectin showed the highest value of bioadhesive force and the taste was acceptable. The characteristics of the B-LF tablets were improved by adding an appropriate amount of xylitol and using the ingredients sieved by a 100-mesh sieve. The therapeutic effect was evaluated by using rats with an ulcer on the oral mucosa. In the present study, swelling on the periphery of the ulcer was observed after administration of the B-LF tablets, and then the ulcer has reduced overall. PMID:17600641

Takahashi, Y; Takeda, C; Seto, I; Kawano, G; Machida, Y

2007-10-01

340

Bilayer tablets of atorvastatin calcium and nicotinic acid: formulation and evaluation.  

PubMed

The objective of the study is to formulate bilayer tablets consisting of atorvastatin calcium (AT) as an immediate release layer and nicotinic acid (NA) as an extended release layer. The immediate release layer was prepared using super disintegrant croscarmellose sodium and extended release layer using hydroxypropylmethyl cellulose (HPMC K100M). Both the matrix and bilayer tablets were evaluated for hardness, friability, weight variation, thickness, and drug content uniformity and subjected to in vitro drug release studies. The amount of AT and NA released at different time intervals were estimated by HPLC method. The bilayer tablets showed no significant change either in physical appearance, drug content or in dissolution pattern after storing at 40 degrees C/75% relative humiding (RH) for 3 months. The release of the drug from the tablet was influenced by the polymer content and it was much evident from thermogravimetry/differential thermal analysis (TG/DTA) analysis. The results indicated that the bilayer tablets could be a potential dosage form for delivering AT and NA. PMID:18827389

Nirmal, Jayabalan; Saisivam, Srinivasan; Peddanna, Chintalapati; Muralidharan, Selvadurai; Godwinkumar, Sundaram; Nagarajan, Muthuraja

2008-10-01

341

Wet granulation fine particle ethylcellulose tablets: effect of production variables and mathematical modeling of drug release.  

PubMed

In the present study, the applicability of fine particle ethylcellulose (FPEC) to produce matrix tablets by a wet granulation technique was evaluated. The effect of various formulation and process variables, such as FPEC content, hardness of the tablet, and solubility of the drug, on the release of drug from these tablets was examined. Tablets were prepared by wet granulation of drug and FPEC in an appropriate mass ratio. Theophylline, caffeine, and dyphylline were selected as nonionizable model drugs with solubilities from 8.3 to 330 mg/mL at 25 degrees C. Ibuprofen, phenylpropanolamine hydrochloride, and pseudoephedrine hydrochloride were selected as ionizable drugs with solubilities from 0.1 to 2000 mg/mL at 25 degrees C. Drug release studies were conducted in 37 degrees C water with UV detection. As the FPEC content and the hardness of the tablets increased, the release rate of the drug decreased. The drug release rate increased with an increase in the solubility of the drug. Model equations, intended to elucidate the drug release mechanism, were fitted to the release data. Parameters were generated and data presented by SAS software. The Akaike Information Criterion was also considered to ascertain the best-fit equation. Fickian diffusion and polymer relaxation were the release mechanisms for nonionizable and ionizable drugs. PMID:12866940

Agrawal, Anjali M; Neau, Steven H; Bonate, Peter L

2003-01-01

342

The development and in vitro evaluation of sustained release tablet formulations of benzydamine hydrochloride and its determination.  

PubMed

A novel oral controlled delivery system for benzydamine hydrochloride (BN) was developed and optimized. Hydrophilic matrix tablets of BN were prepared by using hydroxypropylmethylcellulose (HPMC) and chitosan as polymer substance to achieve required sustained release profile. The matrix tablets were prepared both direct compression and wet granulation method. The influence of matrix forming agents and binary mixtures of them on BN release was investigated. The formulated tablets were characterized by hardness, friability, thickness, weight variation and in vitro drug release. The formulated tablets had acceptable physicochemical characters. The quantity of BN present in the tablets and the release medium were estimated by a simple, sensitive, rapid and validated HPLC method. The dissolution results show that increased amount of polymer resulted in reduced and extended drug release. F7 formulation containing 12.5% HPMC and 12.5 % chitosan with direct compression method is the optimum formulation due to its better targeting profile in terms of release. Higuchi (diffusion) and Hixon-Crowell (erosion) kinetic profiles were achieved and this codependent mechanism of drug release was established. This formulation may provide an alternative for oral controlled delivery of BN and be helpful in the future treatment of primary normoreactive types of inflammation. PMID:20426743

Kose-Ozkan, Cansel; Savaser, Ayhan; Tas, Cetin; Ozkan, Yalcin

2010-09-01

343

Float polishing of optical materials.  

PubMed

The float-polishing technique has been studied to determine its suitability for producing supersmooth surfaces on optical materials, yielding a roughness of <2 A rms. An attempt was made to polish six different materials including fused quartz, Zerodur, and sapphire. The low surface roughness was achieved on fused quartz, Zerodur, and Corning experimental glass-ceramic materials, and a surface roughness of <1 A rms was obtained on O-cut single-crystal sapphire. Presumably, similar surface finishes can also be obtained on CerVit and ULE quartz, which could not be polished satisfactorily in this set of experiments because of a mismatch between sample mounting and machine configuration. PMID:20454201

Bennett, J M; Shaffer, J J; Shibano, Y; Namba, Y

1987-02-15

344

DESIGN AND EVALUATION OF A METRONIDAZOLE CENTRAL CORE MATRIX TABLET  

PubMed Central

In this paper, a study of different concentration of HPMC K 15 M exerts influence on the drug release process from a new controlled drug delivery system has been realized in order to obtain a constant release rate during a prolonged period of time, for a programmed drug release. The drug release profiles obtained for the different batches have shown an interesting relationship between the particle size of the channeling agent used and the length of different operational periods.

Nagaich, Upendra; Chaudhary, Vandana; Tonpay, S.D.; Karki, Roopa

2010-01-01

345

A comparative study of the dissolution characteristics of capsule and tablet dosage forms of melt granulations of paracetamol--diluent effects.  

PubMed

The dissolution characteristics of melt granulations of paracetamol in capsule and tablet dosage form were compared to determine whether the dissolution characteristics of the granules can be actualized by formulating them as rapidly disintegrating tablets. The term melt granulation refers here to the wax-matrix granules that were formed by triturating the drug powder (paracetamol) with a melted carnauba wax. The matrix granules were admixed with diluents (lactose, alpha-cellulose or microcrystalline cellulose) also in granular form to prevent size separation during encapsulation or tableting. The granules were filled into hard gelatin capsules (mean content weight, 500 +/- 6.2 mg) or tableted (mean weight 500 +/- 5.1 mg, and tensile strength 1.36 +/- 0.2 to 1.7 +/- 0.3 MN/m2). The capsules and tablets were subjected to disintegration and in vitro dissolution tests. The dissolution data were analyzed on the basis of zero, first order rate kinetics and Higuchi square root of time relationship. The results showed that the dissolution profiles were generally consistent with a first order rate kinetics (r = 0.95). The first order dissolution rate constants of capsules and tablets of the matrix granules only (without diluents) were 0.31 +/- 0.02 min(-1) and 0.20 +/- 0.03 min(-1), respectively, indicating faster dissolution from the capsules. Therefore, the dissolution characteristics of the matrix particles were not intact after tableting. Addition of diluents to the capsule formulations had no effect on dissolution rates, whereas in the tablets, dissolution rates increased. For instance, inclusion of a diluent up to 50% w/w in the tablets increased the dissolution rate constants to 0.34 +/- 0.04 min(-1) (lactose), 0.42 +/- 0.02 min(-1) (alpha-cellulose), and 0.46 +/- 0.03 min(-1) (microcrystalline cellulose). Thus, alpha-cellulose and microcrystalline cellulose produced greater enhancer effect on the tablet dissolution rates compared to lactose. Both the capsules and the tablets disintegrated rapidly within 2 to 3 minutes. The dissolution enhancer effect of the diluents in the tablets only, relates to the aqueous swelling of the disintegrated particles. PMID:17665854

Uhumwangho, Michael U; Okor, Roland S

2007-01-01

346

Vane Design for the Coastal Ocean Lagrangian (COOL) Float.  

National Technical Information Service (NTIS)

Coastal Ocean Lagrangian (COOL) float is an isopycnal f/h float equipped with vanes to measure vertical velocity. We determined the sensitivity of the float's rotation rate to vertical velocity past it for different vane geometries. The float's response t...

J. Rajamony S. Peterson J. Fontaine D. Hebert T. Rossby

1996-01-01

347

Program Converts VAX Floating-Point Data To UNIX  

NASA Technical Reports Server (NTRS)

VAX Floating Point to Host Floating Point Conversion (VAXFC) software converts non-ASCII files to unformatted floating-point representation of UNIX machine. This is done by reading bytes bit by bit, converting them to floating-point numbers, then writing results to another file. Useful when data files created by VAX computer must be used on other machines. Written in C language.

Alves, Marcos; Chapman, Bruce; Chu, Eugene

1996-01-01

348

Resistant starch as a carrier for oral colon-targeting drug matrix system  

Microsoft Academic Search

In this study, a novel tablet of protein drug matrix for colon targeting was developed using resistant starch as a carrier\\u000a prepared by pre-gelatinization and cross-linking of starch. The effects of pre-gelatinization and cross-linking on the swelling\\u000a and enzymatic degradation of maize starch as well as the release rate of drug from the matrix tablets were examined. Cross-linked\\u000a pre-gelatinized maize

Ling Chen; Xiaoxi Li; Yansheng Pang; Lin Li; Ximei Zhang; Long Yu

2007-01-01

349

The Effects of Buffer Molarity, Agitation Rate, and Mesh Size on Verapamil Release from Modified-Release Mini-Tablets Using USP Apparatus 3  

Microsoft Academic Search

The effects of agitation rate,buffer molarity,and mesh size on the dissolution rate of verapamil hydrochloride from sustained- release matrix tablets were studied using USP Apparatus 3. Eudragit® and Carbopol® were used as rate-retarding polymers in tablets prepared by wet granulation. The study was conducted to determine whether the drugs exhibit similar release charac- teristics when tested under the same dissolution

Sandile M. M. Khamanga; Roderick B. Walker

350

Preview of Mars Curiosity Parade Float  

NASA Video Gallery

Jim Green, Director of the Science Mission Directorate Planetary Systems Division at NASA Headquarters, describes the replica of the Mars Curiosity Rover on the second NASA float in Monday's inaugu...

351

Current Mirror with Programmable Floating Gate.  

National Technical Information Service (NTIS)

Systems and methods are discussed for using a floating-gate MOSFET as a programmable reference circuit. One example of the programmable reference circuit is a programmable voltage reference source, while a second example of a programmable reference circui...

G. J. Serrano P. E. Hasler

2006-01-01

352

Exploring Floating Concrete and Beam Design.  

ERIC Educational Resources Information Center

Presents two construction activities that address both state and federal science standards and encourage students to consider career options in mathematics and science. Includes floating concrete and paper bridge activities. (YDS)

Snell, Billie G.; Snell, Luke M.

2002-01-01

353

Verification of floating-point software  

NASA Technical Reports Server (NTRS)

Floating point computation presents a number of problems for formal verification. Should one treat the actual details of floating point operations, or accept them as imprecisely defined, or should one ignore round-off error altogether and behave as if floating point operations are perfectly accurate. There is the further problem that a numerical algorithm usually only approximately computes some mathematical function, and we often do not know just how good the approximation is, even in the absence of round-off error. ORA has developed a theory of asymptotic correctness which allows one to verify floating point software with a minimum entanglement in these problems. This theory and its implementation in the Ariel C verification system are described. The theory is illustrated using a simple program which finds a zero of a given function by bisection. This paper is presented in viewgraph form.

Hoover, Doug N.

1990-01-01

354

Accelerated degradation of ibuprofen in tablets.  

PubMed

The forced degradation of 11 ibuprofen tablet brands was carried out according to current industry best practices. The results indicated an incompatibility between ibuprofen and two common tablet excipients (polyethylene glycol and polysorbate 80) that were observed to accelerate the degradation of ibuprofen in tablets stored for three weeks at 70°C/75% RH. Studies of binary drug/excipient samples supported the conclusion. One degradant that was observed at increased levels was 4-isobutylacetophenone (4-IBAP), which is a known toxin. PMID:19941407

Cory, Wendy Clevenger; Harris, Corbyn; Martinez, Sabrina

2010-12-01

355

A floating-point technique for extending the available precision  

Microsoft Academic Search

A technique is described for expressing multilength floating-point arithmetic in terms of singlelength floating point arithmetic, i.e. the arithmetic for an available (say: single or double precision) floating-point number system. The basic algorithms are exact addition and multiplication of two singlelength floating-point numbers, delivering the result as a doublelength floating-point number. A straight-forward application of the technique yields a set

T. J. Dekker

1971-01-01

356

Floating drug delivery systems: A review  

Microsoft Academic Search

The purpose of writing this review on floating drug delivery systems (FDDS) was to compile the recent literature with special\\u000a focus on the principal mechanism of floatation to achieve gastric retention. The recent developments of FDDS including the\\u000a physiological and formulation variables affecting gastric retention, approaches to design single-unit and multiple-unit floating\\u000a systems, and their classification and formulation aspects are

Shweta Arora; Javed Ali; Alka Ahuja; Roop K. Khar; Sanjula Baboota

2005-01-01

357

Multiple valued floating potentials of Langmuir probes  

NASA Technical Reports Server (NTRS)

It is shown that Langmuir probes can have three different floating potentials in plasmas produced by a hot filament discharge in a multi-dipole device when the primary and secondary electron currents are comparable. The measured floating potential depends on the probe's initial condition - the most negative and the least negative potentials are found to be stable and the in-between value is found to be unstable. Results are compared to a simple theoretical model.

Nam, Cheol-Hee; Hershkowitz, N.; Cho, M. H.; Intrator, T.; Diebold, D.

1988-01-01

358

Decimal Floating-Point: Algorism for Computers  

Microsoft Academic Search

Decimal arithmetic is the norm in human calculations, and human-centric applications must use a decimal floating-point arithmetic to achieve the same results. Initial benchmarks indicate that some applications spend 50% to 90% of their time in decimal processing, because software decimal arithmetic suffers a 100× to 1000× performance penalty over hardware. The need for decimal floating-point in hardware is urgent.

Michael F. Cowlishaw; Coventry CV

2003-01-01

359

Mixed abstractions for floating-point arithmetic  

Microsoft Academic Search

Floating-point arithmetic is essential for many embedded and safety-critical systems, such as in the avionics industry. Inaccuracies in floating-point calculations can cause subtle changes of the control flow, potentially leading to disastrous errors. In this paper, we present a simple and general, yet powerful framework for building abstractions from formulas, and instantiate this framework to a bit-accurate, sound and complete

Angelo Brillout; Daniel Kroening; Thomas Wahl

2009-01-01

360

Floating distal interphalangeal joint injury: case report.  

PubMed

A 37-year-old man sustained a floating distal interphalangeal (DIP) joint injury to the left index finger. The diagnosis was not confirmed until 3 months after the injury because of minimal deformity of the injured finger. Open reduction and internal fixation of the dorsally displaced floating DIP joint was carried out. Bone union was achieved but radiographs revealed osteoarthritis of the DIP joint. PMID:20724082

Kawamura, Kenji; Omokawa, Shohei; Shimizu, Takamasa; Tanaka, Yasuhito

2010-09-01

361

The Sea Peoples, from cuneiform tablets to carbon dating.  

PubMed

The 13(th) century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ?3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192-1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations. PMID:21687714

Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

2011-01-01

362

Comparison of pharmacokinetics in beagle dogs of nimesulide bilayer tablets with dispersible tablets.  

PubMed

The purpose of this study was to compare the in vitro release and the in vivo pharmacokinetics of bilayer tablets with the conventional dispersible tablets of nimesulide. The tablets were administered to beagle dogs and the plasma levels of nimesulide were determined by high-performance liquid chromatography-MS/MS. The pharmacokinetic parameters were calculated using a noncompartmental model. The bilayer tablets showed a biphasic in vitro release pattern with initial burst release and sustained release following the quasi-Fickian diffusion-based release mechanism. The C(max), t(max), mean residence time (MRT), and area under the curve from 0 to 36 h were 10.8 ± 4.2 ?g/mL, 2.3 ± 1.0 h, 6.7 ± 2.1 h, 81.5 ± 26.7 ?g·h/mL for the bilayer tablets and 14.8 ± 5.8 ?g/mL, 2.7 ± 0.8 h, 5.6 ± 0.9 h, 95.4 ± 44.2 ?g·h/mL for the dispersible tablets. Compared with the dispersible tablets, the bilayer tablets have lower C(max), similar t(max), and longer MRT. The aforementioned pharmacokinetic parameters, especially the MRT demonstrated to be valuable for evaluating the biphasic characteristics. This study provides a promising in vivo evaluation method for the bilayer tablets with biphasic release pattern. PMID:22397600

Yang, M Y; Wang, Y L; Guo, J F; Shan, L; Li, Y; Bai, X Q; Fan, Y Z; Gao, C S

2013-01-01

363

Floating assembly of diatom Coscinodiscus sp. microshells.  

PubMed

Diatoms have silica frustules with transparent and delicate micro/nano scale structures, two dimensional pore arrays, and large surface areas. Although, the diatom cells of Coscinodiscus sp. live underwater, we found that their valves can float on water and assemble together. Experiments show that the convex shape and the 40 nm sieve pores of the valves allow them to float on water, and that the buoyancy and the micro-range attractive forces cause the valves to assemble together at the highest point of water. As measured by AFM calibrated glass needles fixed in manipulator, the buoyancy force on a single floating valve may reach up to 10 ?N in water. Turning the valves over, enlarging the sieve pores, reducing the surface tension of water, or vacuum pumping may cause the floating valves to sink. After the water has evaporated, the floating valves remained in their assembled state and formed a monolayer film. The bonded diatom monolayer may be valuable in studies on diatom based optical devices, biosensors, solar cells, and batteries, to better use the optical and adsorption properties of frustules. The floating assembly phenomenon can also be used as a self-assembly method for fabricating monolayer of circular plates. PMID:22387476

Wang, Yu; Pan, Junfeng; Cai, Jun; Zhang, Deyuan

2012-03-30

364

Floating phenomenon and mode of color appearance  

NASA Astrophysics Data System (ADS)

We found an interesting phenomenon concerning the motion perception and the mode of color appearance. We suppose you are holding a stiff sheet of picture and move it laterally to and fro in front of the eye. Though the picture and all items in it move physically altogether with your hand, your perception is not always so. But when the picture that is a figure appears light-source color mode and a background of object color, a figure appears to slip on a background. We call this a 'floating phenomenon.' We predicted the occurrence of floating phenomenon depends on whether the color is perceived to belong to an object or not. To examine the relation between the floating phenomenon and the mode of color appearance, we measured the luminance threshold of floating phenomenon and the transition luminance between two color modes by constant stimulus method to use a mondrian. Our results show the floating never occurred when the target appeared as object color mode. The floating phenomenon may be caused by the separation of the light-source color from an object or week-belonging.

Aoki, Hironobu; Shinoda, Hiroyuki; Ikeda, Mitsuo

2002-06-01

365

Static headspace gas chromatographic analysis of the residual solvents in gel extrusion module tablet formulations.  

PubMed

A rapid static headspace-gas chromatographic (SHS-GC) method was developed and validated for the quantitation of residual solvents in pharmaceutical gel extrusion module (GEM) tablet formulations. A static headspace sampling technique was utilized to overcome the difficulties imposed by direct injection methods. A Rtx-1701 megabore capillary column was selected to achieve optimal resolution among organic volatile chemicals used commonly in the manufacturing of GEM tablets, residual solvents in the active ingredient and excipients, and other formulation matrix artifacts. A 50-mM pH 3.0 sodium phosphate buffer was used as a sample diluent to minimize matrix effects. The instrumental parameters of the SHS-GC method were optimized for sensitivity and precision. Quantitation was performed by external standard analysis. The SHS-GC method was validated according to regulatory requirements and produced acceptable results with respect to specificity, linearity, range, detection and quantitation limits, precision, and accuracy. PMID:12008147

Li, Zhong; Han, Yieng-Hau; Martin, Gregory P

2002-05-15

366

Suitability of ?-carrageenan pellets for the formulation of multiparticulate tablets with modified release.  

PubMed

?-Carrageenan is a novel pelletisation aid with high formulation robustness and quick disintegration leading to fast drug release unlike the matrix-like release from non-disintegrating microcrystalline cellulose pellets. Compression of pellets into tablets is cost effective. The feasibility of formulating multiparticulate tablets with coated ?-carrageenan pellets was investigated. Pellets containing a highly soluble drug in acid, namely bisacodyl and ?-carrageenan or MCC as pelletisation aid were prepared, enteric coated with a mixture of Kollicoat(®) MAE 30 DP and Eudragit(®) NE 30 D and compressed using silicified microcrystalline cellulose as embedding powder. The effect of coating level, type of pellet core, compression force and punch configurations on drug release were studied. A sufficient coating thickness for ?-carrageenan pellets was necessary to obtain multiparticulate tablets with adequate resistance in the acid stage regardless of the compression pressure used. While ?-carrageenan pellets and their tablets released over 80% of the drug during the neutral stage only about 20-24% was released from MCC pellets and their tablets. The type of punches used (oblong or round) did not significantly influence the drug release from the prepared tablets. Moreover, sufficient prolonged release properties were obtained with ?-carrageenan pellets containing theophylline as a model drug and coated with Kollicoat(®) SR 30 D using Kollicoat(®) IR as pore former. A lower coating level and higher amount of pore former were needed in case of theophylline pellets formulated with MCC as pelletisation aid. The sustained release properties of both coated pellet formulations were maintained after compression at different compression pressures. PMID:21335073

Ghanam, Dima; Kleinebudde, Peter

2011-05-16

367

Mucoadhesive bilayer tablets of propranolol hydrochloride  

Microsoft Academic Search

The purpose of this research was to study mucoadhesive bilayer buccal tablets of propranolol hydrochloride using the bioadhesive\\u000a polymers sodium alginate (Na-alginate) and Carbopol 934P (CP) along with ethyl cellulose as an impermeable backing layer.\\u000a The tablets were evaluated for weight variation, thickness, hardness, friability, surface pH, mucoadhesive strength, swelling\\u000a index, in vitro drug release, ex vivo drug permeation, ex

Vishnu M. Patel; Bhupendra G. Prajapati; Harsha V. Patel; Karshanbhi M. Patel

2007-01-01

368

An empirical model for dissolution profile and its application to floating dosage forms.  

PubMed

A sum of two inverse Gaussian functions is proposed as a highly flexible empirical model for fitting of in vitro dissolution profiles. The model was applied to quantitatively describe theophylline release from effervescent multi-layer coated floating tablets containing different amounts of the anti-tacking agents talc or glyceryl monostearate. Model parameters were estimated by nonlinear regression (mixed-effects modeling). The estimated parameters were used to determine the mean dissolution time, as well as to reconstruct the time course of release rate for each formulation, whereby the fractional release rate can serve as a diagnostic tool for classification of dissolution processes. The approach allows quantification of dissolution behavior and could provide additional insights into the underlying processes. PMID:24613489

Weiss, Michael; Kriangkrai, Worawut; Sungthongjeen, Srisagul

2014-06-01

369

Airship-floated wind turbine  

SciTech Connect

A wind turbine, by use of a tethered airship for support, may be designed for the economical recovery of power at heights of 2,000 feet or more above ground, at which height power density in the wind is typically three times the power density available to a conventionally supported wind turbine. Means can be added to such an airship-floated wind turbine which will permit its generators to be used to meet load demand even during periods of little or no wind. Described to this end is a wind turbine system which combines, among other novel features: a novel tether line system which provides access for men and materials to the supporting airship while in active service, a novel system for providing additional buoyant lift at the nose of the turbine-supporting airship to offset the vertical component of tension induced in the tether line by the downwind force exerted by the turbine blades, a novel bearing assembly at the nose of the supporting airship which permits the airship to rotate as a unit with the turbine it supports without causing a similar rotation of the tether line, a novel turbine airship structure which handles concentrated loads from the turbine efficiently and also permits the safe use of hydrogen for buoyancy, a novel ''space frame'' structure which supports the turbine blades and greatly reduces blade weight, a novel system for controlling turbine blade angle of incidence and for varying blade incidene in synchrony with blade angular position abut the turbine axis to provide greater control over airship movement, a novel system for locating propellor-driven generators out at the wind turbine perimeter and for using lightweight, high-RPM generators to produce electrical energy at a power line frequency, which greatly reduces the weight required to convert turbine blade torque into useful power, and a novel system for incorporating compressed air storage and combustion turbine components into the wind turbine's generator drive systems.

Watson, W. K.

1985-01-01

370

Zero-order release profile of metoclopramide hydrochloride sublingual tablet formulation.  

PubMed

This report describes zero-order approximation for metoclopramide hydrochloride sublingual tablet formulation. Effects of type and concentration of excipients on release were investigated. Study revealed that highest rate of dissolution was attained with crosspovidone and decreased in the order crosspovidone > sodium starch glycolate > ac-di-sol. All formulations demonstrated flush release, except the one containing 10% crosspovidone where a lag time of 0.5?min. was depicted. Increasing the concentration of crosspovidone from 5 to 10% gave the same half-life, whereas kinetics of release changed to zero order. Differential scanning colorimetry and infrared spectroscopy did not reveal any sign of physical or chemical interaction between drug and crosspovidone. In order to study the alignment of polymeric network inside tablet matrix, scanning electron microscopy was performed on the tablet and its cross-section. Matrix with 10% crosspovidone showed higher density of interconnections extending to the interior of core enabling fast and constant release. Hence physicochemical characteristics of crosspovidone could be tailored by varying its concentration, in a way that provided a porous matrix with tight arrangement of polymeric chains, resembling to an assemblage of cylinders with constant apertures, from which zero-order release was approached. PMID:22963706

Latif, Randa

2013-01-01

371

Tabletted polylactide microspheres prepared by a w/o emulsion-spray drying method.  

PubMed

An emulsification-spray drying technique is used to prepare poly(D,L-lactic acid) (PDLLA) microparticles loaded with a water soluble, non-steroidal anti-inflammatory drug (NSAID), sodium naproxen (NaNPX). The method involves the preparation of a w/o emulsion in which the water soluble drug is dissolved in the aqueous dispersed phase, while the polymer is dissolved in the organic continuous phase. As a comparison, microparticles were prepared by spraying a suspension of the drug into an organic solution of the polymer. The spray-dried particles were characterized using SEM, DSC, XRD and in vitro release tests. The spray-dried product was then compressed (direct compression) to obtain controlled release matrix tablets. All microparticles release NaNPX within 30 min. The matrix tablets release the drug in 8-10 h; the matrix tablets characterized by the presence of surfactant (due to the emulsion used to obtain the microparticles) have the highest release rate. PMID:11063418

Giunchedi, P; Gavini, E; Bonacucina, G; Palmieri, G F

2000-01-01

372

The pharmacokinetics of ibuprofen suspension, chewable tablets, and tablets in children with cystic fibrosis  

Microsoft Academic Search

Objectives: The objectives of this study were to compare the pharmacokinetic parameters of ibuprofen administered as a suspension, chewable tablet, or tablet in children with cystic fibrosis and to determine the optimal blood sampling times for measuring ibuprofen peak concentrations. Study design: A single oral 20 mg\\/kg dose of ibuprofen was administered, and blood samples were obtained at 15, 30,

Christy S. Scott; George Z. Retsch-Bogart; Robert P. Kustra; Katie M. Graham; Bradley J. Glasscock; Philip C. Smith

1999-01-01

373

Floating seal system for rotary devices  

DOEpatents

This invention relates to a floating seal system for rotary devices to reduce gas leakage around the rotary device in a duct and across the face of the rotary device to an adjacent duct. The peripheral seal bodies are made of resilient material having a generally U-shaped cross section wherein one of the legs is secured to a support member and the other of the legs forms a contacting seal against the rotary device. The legs of the peripheral seal form an extended angle of intersection of about 10[degree] to about 30[degree] in the unloaded condition to provide even sealing forces around the periphery of the rotary device. The peripheral seal extends around the periphery of the support member except where intersected by radial seals which reduce gas leakage across the face of the rotary device and between adjacent duct portions. The radial seal assembly is fabricated from channel bars, the smaller channel bar being secured to the divider of the support member and a larger inverted rigid floating channel bar having its legs freely movable over the legs of the smaller channel bar forming therewith a tubular channel. A resilient flexible tube is positioned within the tubular channel for substantially its full length to reduce gas leakage across the tubular channel. A spacer extends beyond the face of the floating channel near each end of the floating channel a distance to provide desired clearance between the floating channel and the face of the rotary device. 5 figs.

Banasiuk, H.A.

1983-08-23

374

Floating seal system for rotary devices  

DOEpatents

This invention relates to a floating seal system for rotary devices to reduce gas leakage around the rotary device in a duct and across the face of the rotary device to an adjacent duct. The peripheral seal bodies are made of resilient material having a generally U-shaped cross section wherein one of the legs is secured to a support member and the other of the legs forms a contacting seal against the rotary device. The legs of the peripheral seal form an extended angle of intersection of about 10.degree. to about 30.degree. in the unloaded condition to provide even sealing forces around the periphery of the rotary device. The peripheral seal extends around the periphery of the support member except where intersected by radial seals which reduce gas leakage across the face of the rotary device and between adjacent duct portions. The radial seal assembly is fabricated from channel bars, the smaller channel bar being secured to the divider of the support member and a larger inverted rigid floating channel bar having its legs freely movable over the legs of the smaller channel bar forming therewith a tubular channel. A resilient flexible tube is positioned within the tubular channel for substantially its full length to reduce gas leakage across the tubular channel. A spacer extends beyond the face of the floating channel near each end of the floating channel a distance to provide desired clearance between the floating channel and the face of the rotary device.

Banasiuk, Hubert A. (Chicago, IL)

1983-01-01

375

Simulating strange attraction of acellular slime mould Physarum polycephaum to herbal tablets  

Microsoft Academic Search

Plasmodium of acellular slime mould Physarum polycephalum exhibits traits of wave-like behaviour. The plasmodium’s behaviour can be finely tuned in laboratory experiments by using herbal tablets. A single tablet acts as a fixed attractor: plasmodium propagates towards the tablet, envelops the tablet with its body and stays around the tablet for several days. Being presented with several tablets the plasmodium

Andrew Adamatzky

376

Anti-pollution and antifire floating barrier  

SciTech Connect

The barrier of this invention is formed by barrier sections and each of them can be wound up about a reel or bobbin, which is pivotably mounted within a main floating hollow element, which not only has the task of receiving, transporting, towing, launching and trawling the barrier section housed therein, but also it serves to provide anchoring points for this barrier. Each main barrier element is shaped in the form of a cage-like container provided with at least a side vertical entrance passage , through which a barrier section can be returned inside the container, or this section can be caused to come out, each main floating element thus serving as floating container for the transport of at least one of the barrier sections to or from their use place.

Bossa, E.D.

1981-07-21

377

Floating zone melting of cadmium telluride  

NASA Technical Reports Server (NTRS)

To produce superior crystals of cadmium telluride, floating zone melting in space has been proposed. Techniques required for floating zone melting of cadmium telluride are being developed. We have successfully float-zoned cadmium telluride on earth using square rods. A resistance heater was constructed for forming the molten zone. Evaporation of the molten zone was controlled by adding excess cadmium to the growth ampoule combined with heating of the entire ampoule. An effective method to hold the feed rod was developed. Slow rotation of the growth ampoule was proven experimentally to be necessary to achieve a complete symmetric molten zone. Most of the resultant cylindrical rods were single crystals with twins. Still needed is a suitable automatic method to control the zone length. We tried a fiber optical technique to control the zone length, but experiments showed that application of this technique to automate zone length control is unlikely to be successful.

Chang, Wen-Ming; Regel, L. L.; Wilcox, W. R.

1992-01-01

378

Development of novel floating delivery system based on psyllium: application on metformin hydrochloride.  

PubMed

psyllium, a medicinally active gel forming natural polysaccharide and a dietary fiber has been used as a medicine in myriad of conditions such as constipation and inflammatory bowel syndrome. One of its more recent uses that have received attention has been its ability to reduce blood sugar levels in diabetics. Therefore present work is an attempt to formulate anti diabetic drug Metformin as a controlled release floating delivery making use of pysllium as release retardant and to assist the drug in stabilizing blood sugar level in type II diabetics. Drug and excipients compatibility studies were monitored by thermal analysis using differential scanning calorimeter (DSC) and Fourier transform infra red (FTIR). The DSC thermogram and FTIR of drug and drug-polymer mixture did not reveal any incompatibility. psyllium was tried in different concentrations along with other polymers like HPMC K15M and carbopol 940 to achieve the desired release profile. The total drug: polymer ratio was kept between 1:0.4 to 1:0.5, and different polymer combinations were tried to achieve desired drug release for 12 hours. The prepared tablets were evaluated for in vitro release studies and floating behavior. Our conclusion from the present study indicated that pysllium could potentially be used in conjunction with other polymers to formulate controlled release formulations of anti-diabetic drugs to provide better control over blood glucose levels. PMID:23410070

Rathnanand, Mahalaxmi; Narkhede, Rajkiran; Udupa, N; Kalra, Atin

2013-06-01

379

21 CFR 520.434 - Chlorphenesin carbamate tablets.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Chlorphenesin carbamate tablets. 520.434 Section 520...ANIMAL DRUGS § 520.434 Chlorphenesin carbamate tablets. (a) Specifications. ...contains 400 milligrams of chlorphenesin carbamate. (b) Sponsor. See No....

2013-04-01

380

21 CFR 520.434 - Chlorphenesin carbamate tablets.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Chlorphenesin carbamate tablets. 520.434 Section 520...ANIMAL DRUGS § 520.434 Chlorphenesin carbamate tablets. (a) Specifications. ...contains 400 milligrams of chlorphenesin carbamate. (b) Sponsor. See No....

2010-04-01

381

21 CFR 520.434 - Chlorphenesin carbamate tablets.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Chlorphenesin carbamate tablets. 520.434 Section 520...ANIMAL DRUGS § 520.434 Chlorphenesin carbamate tablets. (a) Specifications. ...contains 400 milligrams of chlorphenesin carbamate. (b) Sponsor. See No....

2009-04-01

382

Formulation Optimization of Hydrodynamically Balanced Oral Controlled Release Bioadhesive Tablets of Tramadol Hydrochloride  

PubMed Central

The directly compressible floating-bioadhesive tablets of tramadol were formulated using varying amounts Carbopol 971P (CP) and hydroxy-propylmethyl cellulose (HPMC), along with other requisite excipients. In vitro drug release profile, floatational characteristics and ex vivo bioadhesive strength using texture analyzer were determined, and systematically optimized using a 32 central composite design (CCD). The studies indicated successful formulation of gastroretentive compressed matrices with excellent controlled release, mucoadhesion and hydrodynamic balance. Comparison of the dissolution profiles of the optimized formulation, with optimal composition of CP:HPMC :: 80.0:125.0, with that of the marketed controlled release formulation other indicated analogy of drug release performance with each other. Validation of optimization study using eight confirmatory experimental runs indicated very high degree of prognostic ability of CCD with mean ± SEM of ?0.06% ± 0.37. Further, the study successfully unravels the effect of the polymers on the selected response variables.

Singh, Bhupinder; Rani, Ashu; Babita; Ahuja, Naveen; Kapil, Rishi

2010-01-01

383

Formulation and In Vitro Characterization of Xanthan Gum-Based Sustained Release Matrix Tables of Isosorbide5- Mononitrate  

Microsoft Academic Search

In the present investigation an attempt has been made to increase therapeutic efficacy, to reduce frequency of administration and to improve patient compliance by developing a sustained release matrix tablets of isosorbide-5-mononitrate. Sustained release matrix tablets of isosorbide-5-mononitrate were developed by using different drug: polymer ratios, such in F1 (1:0.75), F2 (1:1), F3 (1:1.5), F4 (1:1.75) and F6 (1:2). Xanthan

Rajat Kar; Snehamayee Mohapatra; Satyabrata Bhanja; Debjyoti Das; Bhaktibhusan Barik

2010-01-01

384

Floating Breakwaters: State-of-the-Art Literature Review.  

National Technical Information Service (NTIS)

A multitude of conceptual models of floating breakwaters have been proposed without extensive or complete evaluation of most of these concepts. The technical literature regarding floating breakwater applicability and design procedures is fragmentary and s...

L. Z. Hales

1981-01-01

385

Improvements in floating point addition/subtraction operations  

DOEpatents

Apparatus is described for decreasing the latency time associated with floating point addition and subtraction in a computer, using a novel bifurcated, pre-normalization/post-normalization approach that distinguishes between differences of floating point exponents.

Farmwald, P.M.

1984-02-24

386

A New Distillation Algorithm for Floating-Point Summation  

Microsoft Academic Search

The summation of n floating-point numbers is ubiquitous in numerical computations. We present a new distillation algorithm for floating-point summation which is stable, efficient, and accurate. The algorithm iteratively \\

Yong-Kang Zhu; Jun-Hai Yong; Guo-Qin Zheng

2005-01-01

387

The tableting properties of melibiose monohydrate.  

PubMed

In this research, the tableting properties of ?-melibiose monohydrate were studied. Melibiose is a disaccharide which bears structural resemblance to lactose, because they both consist of galactose and glucose monosaccharide subunits. Compactibility and deformation behavior of two melibiose batches from different suppliers were studied and compared with ?-lactose monohydrate and some other typical tableting excipients. Differences in the deformation behavior were determined comparing the shape of the Heckel plots, the yield pressure values and the strain rate sensitivity (SRS) indexes. In addition, the effect of moisture on the tabletability was studied. According to the yield pressures and SRS indexes melibiose was concluded to be fragmenting, even at higher degree than lactose monohydrate. However, the overall deformation behavior of melibiose was found to be similar to that of lactose monohydrate. Increase in moisture content resulted in higher tensile strengths of tablets for both melibiose batches, but it seemed to have more effect on compactibility of the other batch. In conclusion, melibiose has potential to be used as an excipient in tablet formulations. PMID:23994759

Lakio, Satu; Sainio, Janne; Heljo, Petteri; Ervasti, Tuomas; Kivikero, Niina; Juppo, Anne

2013-11-18

388

Fast dispersible/slow releasing ibuprofen tablets.  

PubMed

Eight formulations were developed containing ibuprofen in the form of orally disintegrating tablets. To prevent bitter taste and side effects of the drug, the drug was associated with Phospholipon 80H, a saturated lecithin, by wet granulation. The granules were then coated using different film forming agents (Kollicoat SR 30, Amprac 01, Kollidon 90F, Eudragit RD 100) obtaining four lots 1-4. Coated granules were then formulated with a sweetener (Aspartame), a mannitol-based diluent (Pearlitol SD 200) and Kollidon CL (1-4K) or Explotab (1-4E) were added as superdisintegrants and compacted under low compression force. The eight lots of tablets, 1-4K and 1-4E, were assessed if suitable as oral disintegrating tablets by determination of a range of technological parameters. Wetting and disintegregation time matched with the requirements of EP IV Ed., for almost all these formulations. Dissolution profiles suggested that the combined action of the hydrophobic lecithin and the coating delay the release of the drug from tablets with respect to when it is free or in the form of simple granules. By an appropriate combination of excipients it was thus possible to obtain orally disintegrating tablets and a delayed release of ibuprofen using simple and conventional techniques. PMID:18182280

Fini, Adamo; Bergamante, Valentina; Ceschel, Gian Carlo; Ronchi, Celestino; de Moraes, Carlos Alberto Fonseca

2008-05-01

389

Matrix Metalloproteinase Inhibition Modulates Fibroblast-Mediated Matrix Contraction and Collagen Production In Vitro  

Microsoft Academic Search

PURPOSE. To investigate the effect of matrix metalloproteinase (MMP) inhibition on fibroblast-mediated matrix contraction and production. METHODS. Free-floating fibroblast-populated type I collagen lattices were prepared with human Tenon's capsule fibro- blasts. Lattice areas were photographed and digitally analyzed to indicate the degree of lattice contraction. Quantitative com- petitive reverse transcription-polymerase chain reaction (QCRT-PCR) and enzyme-linked immunosorbent assay (ELISA) were used

Julie T. Daniels; Alison D. Cambrey; Nicholas L. Occleston; Qian Garrett; Roy W. Tarnuzzer; Gregory S. Schultz; Peng T. Khaw

2003-01-01

390

Error analysis of algorithms for matrix multiplication and triangular decomposition using Winograd's identity  

Microsoft Academic Search

Summary  The number of multiplications required for matrix multiplication, for the triangular decomposition of a matrix with partial pivoting, and for the Cholesky decomposition of a positive definite symmetric matrix, can be roughly halved if Winograd's identity is used to compute the inner products involved. Floating-point error bounds for these algorithms are shown to be comparable to those for the normal

R. P. Brent

1970-01-01

391

Design Issues in Division and Other Floating-Point Operations  

Microsoft Academic Search

Floating-point division is generally regarded as a low frequency, high latency operation in typical floating-pointapplications. However, in the worst case, a high latency hardware floating-point divider can contribute an additional 0.50 CPI to asystem executing SPECfp92 applications. This paper presents the system performance impact of floating-point division latency forvarying instruction issue rates. It also examines the performance implications of shared

Stuart F. Oberman; Michael J. Flynn

1997-01-01

392

Comparison of tablets and paper discs for antibiotic sensitivity testing  

Microsoft Academic Search

The value of tablets and paper discs as reservoirs of antimicrobial agents for use in sensitivity testing was compared. Antibiotics that were unstable in paper discs showed no demonstrable loss of activity in tablets over a period of 50 days under adverse storage conditions. The antibiotic content of commercially prepared tablets is very high in comparison with the accepted content

D F Brown; D Kothari

1975-01-01

393

21 CFR 520.1720a - Phenylbutazone tablets and boluses.  

Code of Federal Regulations, 2013 CFR

...1-g tablets, or 2- or 4-g boluses, in dogs and horses. (2) Nos. 000010 and...of 100- or 200-mg or 1-g tablets in dogs and horses. (3) Nos. 000856 and 061623 for use of 100-mg or 1-g tablets in dogs and horses. (4) [Reserved]...

2013-04-01

394

Microporous bilayer osmotic tablet for colon-specific delivery  

Microsoft Academic Search

Microporous bilayer osmotic tablet bearing dicyclomine hydrochloride and diclofenac potassium was developed using a new oral drug delivery system for colon targeting. The tablets were coated with microporous semipermeable membrane and enteric polymer using conventional pan-coating process. The developed microporous bilayer osmotic pump tablet (OPT) did not require laser drilling to form the drug delivery orifice. The colon-specific biodegradation of

Anil Chaudhary; Neha Tiwari; Vikas Jain; Ranjit Singh

2011-01-01

395

Detection of the breakage of pharmaceutical tablets in pneumatic transport.  

PubMed

Pneumatic transport of pharmaceutical tablets is very convenient, compact and greatly reduces contamination. A potential problem, however, is the breakage of a significant fraction of the transported tablets, causing serious product quality problems. Since the flowrate of tablets transported through a given pneumatic transport line increases with gas velocity, lines are often operated at gas velocities slightly below the velocity at which tablets break. Minor changes in operating conditions can have a large effect on the impact resistance of tablets and on the observed tablet breakage rate. Therefore, maintaining a constant gas velocity is not sufficient to keep the tablet breakage rate below an acceptable level. The objective of the present study was to develop a reliable and non-invasive on-line method for the detection of tablet breakage. Pharmaceutical acetaminophen tablets were transported pneumatically in a 0.1 m diameter pipeline consisting of a 5 m vertical and a 4.0 m horizontal section made of either re-enforced PVC or steel. The pipeline flow regime was determined by visual observation through clear pipeline sections. Tablet breakage was quantified by screening tablet samples. Acoustic measurements were recorded at different locations along the pipeline. Analysis of the signals from microphones attached to the wall of the elbow and horizontal section provided a reliable detection of conditions leading to tablet breakage. PMID:16824711

Albion, Katherine; Briens, Lauren; Briens, Cedric; Berruti, Franco

2006-09-28

396

Blinding controlled-release tablets for clinical trials.  

PubMed

The objective of the current study was to develop a method to blind commercially available Wellbutrin SR 150 mg sustained-release tablets for a clinical study. Overcoating was selected as the most appropriate blinding method. Hydroxypropyl methylcellulose (Opadry II) containing red iron oxide and titanium dioxide was applied to the Wellbutrin tablets at coating levels ranging from 0.5% to 4% weight gain. When compared against the uncoated product, no significant differences in drug release were noted over an 8-hr period. Matching placebo tablets, prepared using specially designed tablet tooling, were coated with the same cellulosic polymer that was used for the active. The coated active and placebo tablets were virtually indistinguishable. To test the applicability of this overcoating technique for blinding other controlled release products, the same procedure was used to coat Glucotrol XL 5 mg tablets and Theo-Dur 200 mg tablets. The debossing on the Theo-Dur tablets and the laser-drilled hole on the surface of the Glucotrol tablets prevented blinding. The Theo-Dur tablets were mechanically weak and not able to withstand the coating process. Dissolution testing revealed significantly higher amounts of drug were released from the blinded Glucotrol tablets compared to the unblinded product at the 12 hr time point. The findings from this study suggest that overcoating with pigmented hydroxypropyl methylcellulose may not be useful for blinding all controlled-release tablets. PMID:12602488

Felton, Linda A; Wiley, Cody J

2003-01-01

397

Improving the performance of floating solar pool covers  

SciTech Connect

Experimental and analytical analyses are presented for the evaluation of heat transfer through floating solar swimming pool covers. Two improved floating solar swimming pool cover designs are proposed and investigated in this paper. The results conclusively show that both new cover designs should have significantly better performance than conventional floating solar swimming pool covers.

Cole, M.A.; Lowrey, P. (San Diego State Univ., CA (United States). Dept. of Mechanical Engineering)

1992-11-01

398

40 CFR 63.1043 - Standards-Separator floating roof.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 false Standards-Separator floating roof. 63.1043 Section 63.1043... § 63.1043 StandardsâSeparator floating roof. (a) This section applies...separator or organic-water separator using a floating roof. (b) The separator shall...

2009-07-01

399

40 CFR 63.1063 - Floating roof requirements.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Floating roof requirements. 63.1063 Section...Control Level 2 § 63.1063 Floating roof requirements. The owner or operator who elects to use a floating roof to comply with the...

2010-07-01

400

40 CFR 63.1063 - Floating roof requirements.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Floating roof requirements. 63.1063 Section...Control Level 2 § 63.1063 Floating roof requirements. The owner or operator who elects to use a floating roof to comply with the...

2013-07-01

401

40 CFR 65.44 - External floating roof (EFR).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false External floating roof (EFR). 65.44 Section 65...Storage Vessels § 65.44 External floating roof (EFR). (a) EFR design requirements...material emissions by using an external floating roof shall comply with the design...

2013-07-01

402

40 CFR 65.44 - External floating roof (EFR).  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false External floating roof (EFR). 65.44 Section 65...Storage Vessels § 65.44 External floating roof (EFR). (a) EFR design requirements...material emissions by using an external floating roof shall comply with the design...

2009-07-01

403

40 CFR 65.44 - External floating roof (EFR).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false External floating roof (EFR). 65.44 Section 65...Storage Vessels § 65.44 External floating roof (EFR). (a) EFR design requirements...material emissions by using an external floating roof shall comply with the design...

2010-07-01

404

40 CFR 63.1043 - Standards-Separator floating roof.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Standards-Separator floating roof. 63.1043 Section 63.1043... § 63.1043 StandardsâSeparator floating roof. (a) This section applies...separator or organic-water separator using a floating roof. (b) The separator shall...

2013-07-01

405

40 CFR 63.1043 - Standards-Separator floating roof.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 false Standards-Separator floating roof. 63.1043 Section 63.1043... § 63.1043 StandardsâSeparator floating roof. (a) This section applies...separator or organic-water separator using a floating roof. (b) The separator shall...

2010-07-01

406

40 CFR 63.1063 - Floating roof requirements.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Floating roof requirements. 63.1063 Section...Control Level 2 § 63.1063 Floating roof requirements. The owner or operator who elects to use a floating roof to comply with the...

2009-07-01

407

An Accelerator for Double Precision Floating Point Operations  

Microsoft Academic Search

We describe DPFPA (double precision floating point accelerator) an FPGA based coprocessor interfaced to the CPU through the PCI bus; it is conceived to accelerate the evaluation of double precision floating point operations. This coprocessor is based on two double precision floating point units: a pipelined adder and a pipelined multiplier. The work is part of a global project aimed

Giovanni Danese; Ivo De Lotto; Francesco Leporati; M. Scaricabarozzi; Alvaro Spelgatti

2003-01-01

408

14 CFR 25.535 - Auxiliary float loads.  

Code of Federal Regulations, 2010 CFR

...load must be applied in the plane of symmetry of the float at a point three-fourths...the center of gravity and the plane of symmetry of the float to the radius of gyration...load must be applied in the plane of symmetry of the float at a point...

2009-01-01

409

14 CFR 25.535 - Auxiliary float loads.  

Code of Federal Regulations, 2010 CFR

...load must be applied in the plane of symmetry of the float at a point three-fourths...the center of gravity and the plane of symmetry of the float to the radius of gyration...load must be applied in the plane of symmetry of the float at a point...

2010-01-01

410

14 CFR 23.535 - Auxiliary float loads.  

Code of Federal Regulations, 2010 CFR

...load must be applied in the plane of symmetry of the float at a point three-fourths...the center of gravity and the plane of symmetry of the float to the radius of gyration...load must be applied in the plane of symmetry of the float at a point...

2009-01-01

411

14 CFR 23.535 - Auxiliary float loads.  

Code of Federal Regulations, 2010 CFR

...load must be applied in the plane of symmetry of the float at a point three-fourths...the center of gravity and the plane of symmetry of the float to the radius of gyration...load must be applied in the plane of symmetry of the float at a point...

2010-01-01

412

Spectrophotometric estimation of azithromycin in tablets.  

PubMed

The present manuscript describes a simple, sensitive, accurate, precise and economical visible spectrophotometric method for the estimation of azithromycin from tablet formulation. The method is based on the reduction of potassium permanganate in alkaline medium with azithromycin. The measurement of decrease in absorbance of potassium permanganate at 547 nm was done, as it decolourises upon reduction by azithromycin. The method was used to determine between 2 and 20 ?g/ml of azithromycin in the final measured solution. There is no interference from the ingredients commonly found in azithromycin tablets with this method. The results for the determination of azithromycin in tablets were in good agreement with the labelled quantities and related analytical parameters are calculated. PMID:23626394

Jayanna, B K; Nagendrappa, G; Arunkumar; Gowda, N

2012-07-01

413

Spectrophotometric Estimation of Azithromycin in Tablets  

PubMed Central

The present manuscript describes a simple, sensitive, accurate, precise and economical visible spectrophotometric method for the estimation of azithromycin from tablet formulation. The method is based on the reduction of potassium permanganate in alkaline medium with azithromycin. The measurement of decrease in absorbance of potassium permanganate at 547 nm was done, as it decolourises upon reduction by azithromycin. The method was used to determine between 2 and 20 ?g/ml of azithromycin in the final measured solution. There is no interference from the ingredients commonly found in azithromycin tablets with this method. The results for the determination of azithromycin in tablets were in good agreement with the labelled quantities and related analytical parameters are calculated.

Jayanna, B. K.; Nagendrappa, G.; Arunkumar; Gowda, N.

2012-01-01

414

Subharmonic and Divergent Motions of Floating Platforms.  

National Technical Information Service (NTIS)

Motions of 1/100 and 1/30 scale models of column-stabilized floating platforms in regular waves have been found to fall in two categories: where heave, surge, and pitch motions are in synchronism with the waves, and where major motions are at subharmonic ...

D. Bellows

1973-01-01

415

Floating Tire Breakwater Tests Pickering Beach, Delaware.  

National Technical Information Service (NTIS)

This report documents a 1-week long field monitoring effort conducted at Pickering Beach, Delaware. The purpose of the study was to gain information concerning mooring line response of a floating breakwater subjected to boat-generated waves. Data are comp...

P. J. Grace J. E. Clausner

1987-01-01

416

Residents' perceptions of a night float system  

Microsoft Academic Search

BACKGROUND: A Night Float (NF) system has been implemented by many institutions to address increasing concerns about residents' work hours. The purpose of our study was to examine the perceptions of residents towards a NF system. METHODS: A 115-item questionnaire was developed to assess residents' perceptions of the NF rotation as compared with a regular call month. The categories included

Harish Jasti; Barbara H Hanusa; Galen E Switzer; Rosanne Granieri; Michael Elnicki

2009-01-01

417

Daphnia (zoomed on floating blood cells)  

NSDL National Science Digital Library

These pin drops are the clearly defined blood cells of the Daphnia. We are only able to see the cells with use of a microscope. Keep in mind that the cells are not confined in any blood vessel (called an open circulatory system) and freely float throughout the body.

Katie Hale (CSUF;Biological Sciences)

2007-07-18

418

Managed Floating as a Monetary Policy Strategy  

Microsoft Academic Search

Although there seems to be a broad consensus among economists that purely floating or completely fixed exchange rates (the so-called corner solutions) are the only viable alternatives of exchange rate management, many countries do not behave according to this paradigm and adopt a strategy within the broad spectrum of exchange rate regimes that is limited by the two corner solutions.

Peter Bofinger; Timo Wollmershäuser

2003-01-01

419

Floating--A Key to Survival.  

ERIC Educational Resources Information Center

Described are several activities to be used to help students grasp the concept of floating. The activities include the use of a spring scale to measure the weight of the objects in air, in water, and in salt water, and a discussion of why there are differences in these weights. (DS)

Anderson, Norman

1980-01-01

420

Floating roof tank with rim space seal  

Microsoft Academic Search

This patent describes a vertical cylindrical liquid storage tank having a circular floating roof of smaller diameter than the tank thereby defining a clearance space between the roof edge and the tank wall; a seal joined to the roof and extending upwardly therefrom into slidable contact with the tank wall; the seal completely covering the clearance space; the seal comprising

R. B. Grove; S. W. Peters; M. L. Tellalian

1986-01-01

421

Development of a Mixed Layer Float.  

National Technical Information Service (NTIS)

The purpose of this grant was to finish development of a new type of neutrally buoyant float designed to accurately follow the three dimensional motion of water parcels in the ocean mixed layer. This work was joint with David Farmer, of the Institute of O...

E. A. D'Asaro

1993-01-01

422

The Accuracy of Floating Point Summation  

Microsoft Academic Search

. The usual recursive summation technique is just one of several ways of computing thesum of n floating point numbers. Five summation methods and their variations are analysed here.The accuracy of the methods is compared using rounding error analysis and numerical experiments.Four of the methods are shown to be special cases of a general class of methods, and an error

Nicholas J. Higham

1993-01-01

423

Adaptive floating search methods in feature selection  

Microsoft Academic Search

Abstract A new,suboptimal,search strategy for feature selection is presented. It represents a more,sophisticated version of ‘‘classical’’ floating search algorithms (Pudil et al., 1994), attempts to remove some of their potential deficiencies and facilitates finding a solution even closer to the optimal,one. ” 1999 Elsevier Science B.V. All rights reserved. Keywords: Pattern recognition; Feature selection; Search methods

Petr Somol; Pavel Pudil; Jana Novovicová; Pavel Paclík

1999-01-01

424

Error analysis of floating-point computation  

Microsoft Academic Search

This paper consists of two main sections. In the first the bounds are derived for the rounding errors made in the fundamental floating-point arithmetic operations. In the second, these results are applied in the analysis of a number of computing techniques for the calculation of the eigenvalues of matrices. In each case thecomputed solution is expressed as the exact solution

J. H. Wilkinson

1960-01-01

425

Robust adaptive floating-point geometric predicates  

Microsoft Academic Search

Fast C implementations of four geometric predicates, the 2D and 3D orientation and incircle tests, are publicly avail- able. Their inputs are ordinary single or double precision floating-point numbers. They owe their speed to two fea- tures. First, they employ new fast algorithms for arbitrary precision arithmetic that have a strong advantage over other software techniques in computations that manipulate

Johnathan Richard Shewchuk

1996-01-01

426

Submerged floating tunnels (SFTs) for Norwegian fjords  

Microsoft Academic Search

Submerged floating tunnels (SFTs) weigh roughly the same as the surrounding water. The loads on the tunnel depend on the variation of the forces on the tunnel. The forces come from variation in traffic, current, temperature, waves, weight of water, weight of concrete, growth on the tunnel, wear of asphalt, dust and debris, relaxation of prestress and shrinkage and creep

Per Tveit

2010-01-01

427

A New Concept in Floating Production Systems  

Microsoft Academic Search

This paper describes a tandem hull floating production platform which combines the large deck space and high payload carrying advantages of a monohull vessel with some of the low wave induced motion characteristics that are typical of semisubmersible vessels. The basic features of the tandem hull platform are presented and comparisons made with the motion characteristics of various other hull

M. H. Patel; J. I. Montgomery; M. S. Worley

1984-01-01

428

Mucoadhesive bilayer tablets of propranolol hydrochloride.  

PubMed

The purpose of this research was to study mucoadhesive bilayer buccal tablets of propranolol hydrochloride using the bioadhesive polymers sodium alginate (Na-alginate) and Carbopol 934P (CP) along with ethyl cellulose as an impermeable backing layer. The tablets were evaluated for weight variation, thickness, hardness, friability, surface pH, mucoadhesive strength, swelling index, in vitro drug release, ex vivo drug permeation, ex vivo mucoadhesion, and in vivo pharmacodynamics in rabbits. Tablets containing Na-alginate and CP in the ratio of 5:1 (F2) had the maximum percentage of in vitro drug release without disintegration in 12 hours. The swelling index was proportional to Na-alginate content and inversely proportional to CP content. The surface pH of all tablets was found to be satisfactory (7.0 +/- 1.5), close to neutral pH; hence, buccal cavity irritation should not occur with these tablets. The mechanism of drug release was found to be non-Fickian diffusion and followed zero-order kinetics. The formulation F4 was optimized based on good bioadhesive strength (28.9 +/- 0.99 g) and sustained in vitro drug permeation (68.65% +/- 3.69% for 12 hours). The behavior of formulation F4 was examined in human saliva, and both the drug and the buccal tablet were found to be stable. The formulation F4 was applied to rabbit oral mucosa for in vivo studies. The formulation inhibited isoprenaline-induced tachycardia. The studies conducted in rabbits confirmed the sustained release as compared with intravenous administration. PMID:17915827

Patel, Vishnu M; Prajapati, Bhupendra G; Patel, Harsha V; Patel, Karshanbhi M

2007-01-01

429

Water hyacinth: a possible alternative rate retarding natural polymer used in sustained release tablet design  

PubMed Central

In recent years natural polymers have been widely used because of their effectiveness and availability over synthetic polymers. In this present investigation matrix tablets of Metformin hydrochloride were formulated using Water hyacinth powder and its rate retardant activity was studied. Tablets were prepared using wet granulation method with 8% starch as granulating agent and 5, 10, 15, 20, 25 and 30% of Water hyacinth powder to the drug. In preformulation study, angle of repose, Carr's Index and Hausner ratio were calculated. Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) studies were performed and no interactions were found between drug and excipients. Weight variation, friability, hardness, thickness, diameter, and in vitro release study were performed with the prepared matrix tablets. Dissolution studies were conducted using USP type II apparatus at a speed of 100 rpm at 37°C ± 0.5 temperature for 8 h. Though all the formulations comply with both BP and USP requirements, formulation F-1 (5% of Water hyacinth) was the best fitted formula. The drug release patterns were explained in different kinetic models such as Zero order, First order, Higuchi, Hixson Crowell, and Korsmeyer-Peppas equations. The current investigation implies that Water hyacinth has the potential to be used as a rate-retarding agent in sustained release drug formulations.

Khatun, Sabera; Sutradhar, Kumar B.

2014-01-01

430

Water hyacinth: a possible alternative rate retarding natural polymer used in sustained release tablet design.  

PubMed

In recent years natural polymers have been widely used because of their effectiveness and availability over synthetic polymers. In this present investigation matrix tablets of Metformin hydrochloride were formulated using Water hyacinth powder and its rate retardant activity was studied. Tablets were prepared using wet granulation method with 8% starch as granulating agent and 5, 10, 15, 20, 25 and 30% of Water hyacinth powder to the drug. In preformulation study, angle of repose, Carr's Index and Hausner ratio were calculated. Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) studies were performed and no interactions were found between drug and excipients. Weight variation, friability, hardness, thickness, diameter, and in vitro release study were performed with the prepared matrix tablets. Dissolution studies were conducted using USP type II apparatus at a speed of 100 rpm at 37°C ± 0.5 temperature for 8 h. Though all the formulations comply with both BP and USP requirements, formulation F-1 (5% of Water hyacinth) was the best fitted formula. The drug release patterns were explained in different kinetic models such as Zero order, First order, Higuchi, Hixson Crowell, and Korsmeyer-Peppas equations. The current investigation implies that Water hyacinth has the potential to be used as a rate-retarding agent in sustained release drug formulations. PMID:24966835

Khatun, Sabera; Sutradhar, Kumar B

2014-01-01

431

Formulation and Evaluation of Bi-layer Tablet of Metoclopramide Hydrochloride and Ibuprofen  

PubMed Central

The aim of this study was to prepare bi-layer tablet of Metoclopramide Hydrochloride (MTH) and Ibuprofen (IB) for the effective treatment of migraine. MTH and IB were formulated as immediate and sustained release layer respectively. MTH was formulated as immediate release layer by using various disintegrants like Ac-Di-Sol, Polyplasdone XL, Explotab, Agar and Gellan Gum. Treated form of gellan gum and agar was prepared and compared for their disintegrant efficiency with other disintegrants. IB was formulated as sustained release layer using hydrophilic matrix (hydroxypropylmethylcellulose [HPMC K4M]). The effect of concentration of hydrophilic matrix (HPMC K4M), binder (polyvinylpyrollidone [PVP K30]) and buffer (sodium bicarbonate) on IB release was studied. The dissolution study of sustained release layer showed that an increasing amount of HPMC or PVP K30 results in reduced IB release. The inclusion of buffer (sodium bicarbonate) enhanced the release of IB from sustained release layer. The rational for formulation of bi-layer tablet of these two drugs in combination was (1) MTH increases the absorption of acidic non-steroidal anti-inflammatory drug (NSAID) by increasing gastric motility. So sequential release of MTH (as immediate release) and IB (as sustained release) was suitable for treatment of migraine. (2) MTH was degraded when prolonged contact with acidic NSAID. Bi-layer tablet was suitable for preventing direct contact of these two drugs and thus to maximize the efficacy of combination of two drugs for migraine.

Shiyani, Bhavesh; Surana, Sanjay

2008-01-01

432

Mössbauer spectra of tin in float glass  

NASA Astrophysics Data System (ADS)

Tin is not a major constituent of window glass, but is found at high concentrations in the lower surface of float glass which has been in contact with the molten tin bath. It does not extend far into the surface, but causes the physical and chemical behaviour to differ from that of the upper surface. It is important, therefore, to understand the structural role of tin in silicate glasses and thus its effect on various properties. Mössbauer spectra were taken of three series of glassy materials, namely binary glasses (SnO and SiO2) in varying proportions, re-melted float glass containing tin, and float glass from a production plant. The binary glasses contained between 20 and 70% tin which was found to be mainly Sn2+, with very small amounts of Sn4+ in some of them. The spectra showed a small decrease in isomer shift with increase in tin content, which is ascribed to the change in molar volume. The re-melted samples were float glass which was mixed with stannous oxalate in appropriate conditions to try and maintain tin in the 2+ state, and contained up to 15% tin by weight. The spectra show both Sn4+ and Sn2+ with rather more in the 4+ oxidation state. The change in the spectra as a function of temperature revealed a large difference in the f-factor (and hence the chemical binding) of the two states. A series of spectra was taken between 17.5 and 900 K for the sample containing 15% tin. From the absorption as a function of temperature the f-factor was determined for both oxidation states, and hence enabled the relative amounts of Sn4+ and Sn2+ present in each sample to be estimated. Measurements of the shift as a function of temperature were also made. The float samples were surface material produced by grinding away all but 0.1 mm of the lower surface of industrially produced float glass. The Mössbauer spectra showed them to be predominantly Sn2+, as expected from the reducing atmosphere in the float plant. The concentration and oxidation state of the tin may be estimated from the value of the f-factors and isomer shifts.

Johnson, J. A.; Johnson, C. E.; Williams, K. F. E.; Holland, D.; Karim, M. M.

1995-12-01

433

Evaluation of the performance characteristics of bilayer tablets: Part II. Impact of environmental conditions on the strength of bilayer tablets.  

PubMed

Ambient air humidity and temperature are known to influence the mechanical strength of tablets. The objective of this work is to understand the influence of processing parameters and environmental conditions (humidity and temperature) on the strength of bilayer tablets. As part of this study, bilayer tablets were compressed with different layer ratios, dwell times, layer sequences, material properties (plastic and brittle), first and second layer forces, and lubricant concentrations. Compressed tablets were stored in stability chambers controlled at predetermined conditions (40C/45%RH, 40C/75%RH) for 1, 3, and 5 days. The axial strength of the stored tablets was measured and a statistical model was developed to determine the effects of the aforementioned factors on the strength of bilayer tablets. As part of this endeavor, a full 3?×?2(4) factorial design was executed. Responses of the experiments were analyzed using PROC GLM of SAS (SAS Institute Inc, Cary, North Carolina, USA). A model was fit using all the responses to determine the significant interactions (p?tablets. For Avicel-lactose and lactose-Avicel tablets, tablet strength decreased with the increasing humidity and storage time. But for lactose-lactose tablets, due to the formation of solid bridges upon storage, an increase in tablet strength was observed. Significant interactions were observed between processing parameters and storage conditions on the strength of bilayer tablets. PMID:22965660

Kottala, Niranjan; Abebe, Admassu; Sprockel, Omar; Bergum, James; Nikfar, Faranak; Cuitiño, Alberto M

2012-12-01

434

Fast disintegrating crystalline solid dispersions of simvastatin for incorporation into orodispersible tablets  

PubMed Central

Aim: Spray dried solid dispersion (SDP) of crystalline simvastatin (SIM) in a fast disintegrating matrix of superdisintegrants was studied as a method to enhance SIM dispersibility, rheology, compactibility and compressibility for incorporation into orodispersible tablets (ODTs). Materials and Methods: The superdisintegrants investigated were crospovidone (CP), sodium starch glycollate (SSG) and calcium silicate (CS) were spray dried with simvastatin to form SDPs. Results: The SDPs were characterized and the median particle size of SDPs was similar or greater than the SIM, contributing to good rheology of SDPs, while the low bulk density of SDPs indicated a high compactibility. Interestingly electron micrographs for SDPs showed a CP or CS carrier coating of the SIM crystals, contributing to its rheology. Thermal analysis and X-ray diffraction confirmed that SIM was crystalline in the SDPs and no interaction between SIM and any of the carrier(s) was shown by Fourier transform-infra red. Drug content analysis showed a SIM content of 90-95% in SDPs containing CP or CS, while a higher SIM content of 143% was found in SDP containing SSG. When formulated as ODTs, blend containing SIM SDPs in CP showed ease of tableting, regardless of the turret speed. In comparison, tablet blend consisting of a physical mix (PM) of SIM and CP could only be tableted at the lower turret speed of 7 rpm. ODTs formulated using SIM SDPs in CP showed a higher extent of dissolution, compared to the ODTs containing corresponding PM or the commercially available SIM Zocor® tablets (ANOVA, P < 0.05). Conclusion: SDP using disintegrants as carriers may offer an alternative formulation approach for ODTs of poorly soluble drugs.

Pabari, Ritesh M; Jamil, Asha; Kelly, John G; Ramtoola, Zebunnissa

2014-01-01

435

Formulation and Evaluation of Chondroitin Sulphate Tablets of Aceclofenac for Colon Targeted Drug Delivery  

PubMed Central

The aim of the present study was to develop a single unit, site-specific matrix tablets of aceclofenac allowing targeted drug release in the colon with a microbially degradable polymeric carrier, chondroitin suphate (CS) and to coat the optimized batches with a pH dependent polymeric. The tablets were prepared by wet granulation method using starch mucilage as a binding agent and HPMC K-100 as a swellable polymer. Chondroitin Sulphate and drug and physical mixture were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The tablets were tested for their in-vitro dissolution characteristics in various simulated gastric fluids for their suitability as a colon-specific drug delivery system and also the tablets were evaluated for physicochemical properties, drug content, water percentage swelling and erosion characteristics. The dissolution data demonstrates that the 10% w/w increase in coating level of the pH dependent polymer (Eudragit L-100 and Eudragit S-100 in a ratio of 1 : 4 prevented the drug release in the simulated gastric fluid (pH 1.2-SGF) and the simulated intestinal fluid (pH 7.4-SIF). The dissolution rate of the tablet is dependent upon the concentration of Chondroitin sulphate in the simulated colonic fluid (SCF). The rapid increase in release of aceclofenac in SCF was revealed as due to the degradation of the Chondroitin sulphate membrane by bacterial enzymes. The studies confirmed that, the designed system could be used potentially as a carrier for colon delivery of aceclofenac by regulating drug release in stomach and the small intestine.

Ramasamy, Thiruganesh; Subbaih Khandasamy, Umadevi; Shanmugam, Suresh; Ruttala, Himabindhu

2012-01-01

436

Miconazole mucoadhesive tablet for oropharyngeal candidiasis  

PubMed Central

Oropharyngeal candidiasis is a commonly encountered problem in daily clinical practice. Topical therapies for oropharyngeal candidiasis are considered preferable to systemic therapies in most patient populations. However, traditional topical therapies have limitations including short contact time with the oral mucosa and the need for multiple doses each day. Miconazole mucoadhesive tablet has recently been approved in Europe (Loramyc®) and the USA (Oravig™) for the treatment of oropharyngeal candidiasis. This tablet adheres to the oral mucosa and provides sustained local release of miconazole over a period of several hours with just one daily application. This article reviews the pharmacology, safety and efficacy of this novel agent.

Lalla, Rajesh V; Bensadoun, Rene-Jean

2011-01-01

437

Formulation and evaluation of bilayer tablet by using melt granulation technique for treatment of diabetes mellitus  

PubMed Central

The objective of present study was to prepare and characterize Bilayer tablet formulation containing Metformin HCl in extended release matrix form and Pioglitazone HCl in immediate release form for the treatment of diabetes mellitus. Different formulations containing Metformin HCl were manufactured using 32 factorial designs. Influence of hydrophilic carrier, hydrophobic polymer on drug release was studied. Immediate release layer of Pioglitazone was optimized using different super disintegrants. All formulations were evaluated for percentage drug release. Optimization results indicated that release rate of Metformin is directly proportional to the levels of Eudragit S 100 and PEG 6000. Results confirmed that Bilayer tablet formulation containing extended release of Metformin HCl and immediate release of Pioglitazone HCl could be developed by using melt granulation technique.

Patel, Dhruvita; Patel, Ankita; Solanki, Trupti

2012-01-01

438

Release characteristics of quetiapine fumarate extended release tablets under biorelevant stress test conditions.  

PubMed

The aim of the present work was the investigation of robustness and reliability of drug release from 50 to 400 mg quetiapine extended release HPMC matrix tablets towards mechanical stresses of biorelevant intensity. The tests were performed under standard conditions (USP apparatus II) as well as under simulated gastrointestinal stress conditions. Mechanical stresses including pressure and agitation were applied by using the biorelevant dissolution stress test apparatus as it has been introduced recently. Test algorithms already established in previous studies were applied to simulate fasting gastrointestinal conditions. The dissolution experiments demonstrated striking differences in the product performance among standard and stress test conditions as well as dose strengths. In USP apparatus II, dissolution profiles were affected mainly by media pH. The dissolution experiments performed in biorelevant dissolution stress test device demonstrated that stress events of biorelevant intensity provoked accelerated drug release from the tablets. PMID:24297600

Garbacz, Grzegorz; Kandzi, Anna; Koziolek, Mirko; Mazgalski, Jaros?aw; Weitschies, Werner

2014-02-01

439

Novel chewable sustained-release tablet containing verapamil hydrochloride.  

PubMed

The aim of this research is to produce a compactable self-sealing chewable tablet of verapamil hydrochloride. Tablets were prepared by compressing beads coated with multiple layers including drug, hydroxypropyl methylcellulose, polyethylene oxide, ethylcellulose, lactose, and sodium starch glycolate. Dissolution studies were carried out according to the USP XXII paddle method for 14 h. A new tablet formulation was evaluated in three different forms: 1) whole tablet, 2) crushed tablet using a commercial tablet crusher, and 3) tablet chewed in the mouth and then expelled into dissolution fluid. Sustained release from the new formulation was maintained and was similar in all three different treatments, and similar to drug release from intact commercially available Isoptin SR, but crushing or chewing destroyed the sustained release property of Isoptin SR (as expected). This new formulation can be administered either by swallowing the whole tablet or by first crushing or chewing the tablet. Controlled release properties of this new formulation do not change by chewing or crushing the tablet first. Such a tablet could be valuable for all patients including those who have difficulty swallowing, such as pediatrics a