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Synthesis, Characterization and Evaluation of Starch Acetate as Rate Controlling Matrix Former for Controlled Release of Nifedipine

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

Starch acetate with a degree of s ubstitution of 1.48 to 1.50 could be synthesized by acetylation of potato starch with acetic anhydride. Matrix tablets of nifedipine (20 mg) prepared employing starch acetate as matrix former in different proportions gave slow and controll ed release over more than 24 h. Nifedipine release was diffusion controlled and dependent on strength (%) of starch acetate and type of diluent in the tablets. Non-Fickian diffusion was th e release mechanism from thes e tablets. A good linear relationship was observed between percent of polymer, starch acetate and release rate (K 0 ) of the matrix tablets. Release rate of the matrix tablets was stab le and unaltered during sh ort time accelerated stability study. Starch acetate was found suitabl e as matrix former for controlled release and the matrix tablets of nifedipine formulated employing starch acetate gave controlled release of nifedipine over 24 h and fulfilled the official release specification of nifedipine extended release tablets.