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Pharmacokinetic Evaluation of Starch Acetate Microcapsules of Nifedipine for In Vivo Controlled Release

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

Nifedipine, an effective and widely prescribed antianginal drug requires controlled release formulation owing to its short biological half life 2.5 h and its rapid elimination. Starch acetate coated microcapsules of nifedipine exhibited good controlled release characteristics in vitro by providing slow release of nifedipine over 24 h. The objective of present study is to evaluate the pharmacokinetics of starch acetate microcapsules of nifedipine in comparison to nifedipine soft capsules (as reference standard) with a view to evaluate the release retarding and rate controlling efficiency of starch acetate in vivo. Nifedipine absorption was rapid with a rate constant (Ka) of 2.05 h-1 in case of soft capsules, whereas with starch acetate microcapsules, the absorption was slow over longer periods of time with a Ka of 0.177 h-1. MRT was increased from 2.5 h for soft capsules to 9.6 h with starch acetate microcapsules indicating longer stay of drug in the body, when administered as starch acetate microcapsules. The relative bioavailability of nifedipine from starch acetate microcapsules was (140.94%), when compared to soft capsules (100%). Starch acetate microcapsules exhibited good release retarding and rate controlling effect in vivo. Nifedipine was released and absorbed slowly over longer periods of time in vivo resulting in the maintainance of serum concentrations within a narrow range over longer periods of time.