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Synthesis, Characterization and Evaluation of Starch Acetate as Microen-capsulating Agent for Controlled Release of Nifedipine

K. P. R. Chowdary and G. V. Radha

Starch acetate with a degree of substitution about 1.5 could be synthesized by acetylation of potato starch with acetic anhydride. Starch acetate microcapsules of ni fedipine were prepared by an industrially feasible emulsification-solvent evaporatio n method and the microcapsules were studied with a view to evaluate starch acetate as microencapsulating agent. The starch acetate mi crocapsules prepared are spherical, discrete, free flowing and multinucleate, m onolithic type. Microencapsu lation efficiency was in the range 97-100%. Nifedipine release from the microcapsules was slow over 24 h and depended on core : coat ratio, wall thickness and size of the microcapsule s. Drug release was by Fickian diffusion mechanism. Good linear relationships were observed between wa ll thickness of the microcapsules and release rate. Starch acetate was found suitable as microencapsu lating agent and the starch acetate microcapsules exhibited good controlled release characteristics.