EUDRAGIT MICROCAPSULES OF NIFEDIPINE AND ITS DISPERSIONS IN HPMC-MCC - PHYSICOCHEMICAL CHARACTERIZATION AND DRUG-RELEASE STUDIES

Nifedipine and its solid dispersions in hydroxypropyl methyl cellulose -microcrystalline cellulose (HPMC-MCC) were microencapsulated with Eud ragit RL PM by an emulsion solvent evaporation method. The microcapsul es are spherical, discrete, free flowing, and covered with a continuou s coating of the polymer. XRD and DTA indicated the presence of nifedi pine in solution form in the solid dispersions and their microcapsules . No chemical interaction between nifedipine and excipients in the mic rocapsules was observed. Nifedipine as such and its microcapsules gave very slow release because of its highly crystalline nature and poor s olubility. Solid dispersion in HPMC-MCC gave fast and rapid dissolutio n of nifedipine. When these solid dispersions were microencapsulated a slow, controlled and complete release over a period of 12 hr was obse rved from the resulting microcapsules. Drug release depended on the pr oportion of HPMC-MCC in the solid dispersion used as a core, coat:core ratio, and size of the microcapsules. Release was independent of pH a nd ionic strength. Drug release was governed by diffusion rate and fol lowed first-order kinetics.