CONTROLLED NIFEDIPINE RELEASE FROM MICROCAPSULES OF ITS DISPERSIONS IN PVP-MCC AND HPC-MCC

Nifedipine and its solid dispersions in polyvinyl-pyrrolidone-microcry stalline cellulose (PVP-MCC) and hydroxypropyl cellulose microcrystall ine cellulose (HPC-MCC) were microencapsulated with cellulose acetate by an emulsion solvent evaporation method. The microcapsules are spher ical, discrete and free flowing. Nifedipine as such and its microcapsu les gave very slow release because of its highly crystalline nature an d poor solubility. Solid dispersion in PVP-MCC and HPC-MCC gave fast a nd rapid dissolution of nifedipine. When these solid dispersions were microencapsulated,a slow, controlled and complete release over a perio d of 12 hours was observed from the resulting microcapsules. Drug rele ase depended on the proportion of PVP-MCC and HPC-MCC in the solid dis persions used as corer coat : core ratio and size of the microcapsules and the release was pH independent. Drug release was governed by diff usion rate and followed first-order kinetics.