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1.  In vitro Dissolution Studies on Solid Dispersions of Mefenamic Acid 
Solid dispersions of mefanamic acid with a water-soluble polymer polyvinyl pyrrolidine and a super disintegrant, primojel were prepared by common solvent and solvent evaporation methods employing methanol as the solvent. The dissolution rate and dissolution efficiency of the prepared solid dispersions were evaluated in comparison to the corresponding pure drug. Solid dispersions of mefenamic acid showed a marked enhancement in dissolution rate and dissolution efficiency. At 1:4 ratio of mefenamic acid-primojel a 2.61 fold increase in the dissolution rate of mefenamic acid was observed with solid dispersion. The solid dispersions in combined carriers gave much higher rates of dissolution than super disintegrants alone. Mefanamic acid-primojel-polyvinyl pyrrolidine (1:3.2:0.8) solid dispersion gave a 4.11 fold increase in the dissolution rate of mefenamic acid. Super disintegrants alone or in combination with polyvinyl pyrrolidine could be used to enhance the dissolution rate of mefenamic acid.
PMCID: PMC3267315  PMID: 22303074
Dissolution rate; mefenamic acid; polyvinyl pyrrolidone; solid dispersions
2.  Formulation and Characterization of Rifampicin Microcapsules 
Rifampicin biodegradable microcapsules were prepared by feasible emulsification-ionic gelation method for a novel controlled release product. Sodium alginate and Carbopol 974P were used as coating polymers in different ratios 1:1, 1:2, 1:3 and 1:4 to obtain elegant microcapsules. The formulations were characterized for encapsulation efficiency, drug loading, sieve analysis, scanning electron microscopy and in vitro release studies. The microcapsules were discrete, large, almost spherical and free flowing with encapsulation efficiency in the range of 75% to 89%, drug loading 75% to 86% and size 440 μm to 500 μm. Rifampicin release from these microcapsules was slow and extended over longer periods of time depending on the polymer coat. Drug release was diffusion controlled and followed first order kinetics. The formulation MC1 with a coating ratio of 1:1 (Sodium alginate: Carbopol 974P) was found to be suitable for oral controlled release.
doi:10.4103/0250-474X.62240
PMCID: PMC2883207  PMID: 20582197
Carbopol 974P (CP); microcapsule; rifampicin; Sodium Alginate (SA)
3.  Tablet formulation studies on nimesulide and meloxicam-cyclodextrin binary systems 
AAPS PharmSciTech  2007;8(2):E71-E77.
The objective of this work was to develop tablet formulations of nimesulide-β-cyclodextrin (NI-β-CD) and meloxicam-γ-cyclodextrin (ME-γ-CD) binary systems. In the case of nimesulide, 3 types of binary systems—physical mixtures, kneaded systems, and coevaporated systems—were studied. In the case of meloxicam, 2 types of binary systems—physical mixtures and kneaded systems—were investigated. Both drug-CD binary systems were prepared at 1∶1 and 1∶2 molar ratio (1∶1M and 1∶2M) and used in formulation studies. The tablet formulations containing drug-CD binary systems prepared by the wet granulation and direct compression methods showed superior dissolution properties when compared with the formulations of the corresponding pure drug formulations. Overall, the dissolution properties of tablet formulations prepared by the direct compression method were superior to those of tablets prepared by the wet granulation method. Selected tablet formulations showed good stability with regard to drug content, disintegration time, hardness, and in vitro dissolution properties over 6 months at 40°C±2°C and 75% relative humidity.
doi:10.1208/pt0802036
PMCID: PMC2750375  PMID: 17915821
Nimesulide; meloxicam; cyclodextrins; tablet formulations; dissolution properties; stability studies
4.  Design and in vitro and in vivo evaluation of mucoadhesive microcapsules of glipizide for oral controlled release: A technical note 
AAPS PharmSciTech  2003;4(3):87-92.
Conclussion
Thus, large spherical microcapsules with a coat consisting of alginate and a mucoadhesive polymer (sodium CMC, methylcellulose, Carbopol, or HPMC) could be prepared by an orifice-ionic gelation process. The microcapsules exhibited good mucoadhesive properties in an in vitro test. Glipizide release from these mucoadhesive microcapsules was slow and extended over longer periods of time and depended on composition of the coat. Drug release was diffusion controlled and followed zero-order kinetics after a lag, period of 1 hour. In the in vivo evaluation, alginate-Carbopol microcapsules could sustain the hypoglycemic effect of glipizide over a 14-hour period. These mucoadhesive microcapsules are, thus, suitable for oral controlled release of glipizide.
doi:10.1208/pt040339
PMCID: PMC2750632  PMID: 14621971
mucoadhesive microcapsules; glipizide; controlled release
5.  β-cyclodextrin complexes of celecoxib: Molecular-modeling, characterization, and dissolution studies 
AAPS PharmSci  2004;6(1):68-76.
Celecoxib, a specific inhibitor of cycloxygenase-2 (COX-2) is a poorly water-soluble nonsteroidal anti-inflammatory drug with relatively low bioavailability. The effect of β-cyclodextrin on the aqueous solubility and dissolution rate of celecoxib was investigated. The possibility of molecular arrangement of inclusion complexes of celecoxib and β-cyclodextrin were studied using molecular modeling and structural designing. The results offer a better correlation in terms of orientation of celecoxib inside the cyclodextrin cavity. Phase-solubility profile indicated that the solubility of celecoxib was significantly increased in the presence of β-cyclodextrin and was classified as AL-type, indicating the 1∶1 stoichiometric inclusion complexes. Solid complexes prepared by freeze drying, evaporation, and kneading methods were characterized using differential scanning calorimetry, powder x-ray diffractometry, and scanning electron microscopy. In vitro studies showed that the solubility and dissolution rate of celecoxib were significantly improved by complexation with β-cyclodextrin with respect to the drug alone. In contrast, freeze-dried complexes showed higher dissolution rate than the other complexes.
doi:10.1208/ps060107
PMCID: PMC2750942  PMID: 15198508
celecoxib; β-cyclodextrin; complexation; molecular-modeling; phase solubility; characterization; dissolution rate
6.  Physicochemical characterization and dissolution properties of nimesulide-cyclodextrin binary systems 
AAPS PharmSciTech  2003;4(1):6-17.
The objective of this work is physicochemical characterization of nimesulide-cyclodextrin binary systems both in solution and solid state and to improve the dissolution properties of nimesulide (N) via complexation with α-, β, and γ-cyclodextrins (CDs). Detection of inclusion complexation was done in solution by means of phase solubility analysis, mass spectrometry, and 1H nuclear magnetic resonance (1H-NMR) spectroscopic studies, and in solid state using differential scanning calorimetry (DSC), powder x-ray diffractometry (X-RD), scanning electron microscopy (SEM), and in vitro dissolution studies. Phase solubility, mass spectrometry and 1H-NMR studies in solution revealed 1∶1 M complexation of N with all CDs. A true inclusion of N with β-CD at 1∶2 M in solid state was confirmed by DSC, powder X-RD and SEM studies. Dissolution properties of N-CD binary systems were superior when compared to pure N.
doi:10.1208/pt040102
PMCID: PMC2750298  PMID: 12916912
nimesulide; cyclodextrins; physicochemical characterization; dissolution properties

Results 1-6 (6)