PREPARATION AND EVALUATION OF ZIDOVUDINE EXTENDED RELEASE MATRIX TABLETS

The purpose of present study was to formulate and evaluate Zidovudine extended release matrix tablets by using different polymer ratios viz., HPMC and Isabgol. Preformulation study was done immediately and results were directed for future course of formulation. Based on preformulations study different formulations were prepared by using selected excipients. Powder mixture was evaluated for bulk density, tapped density, compressability index, hausners ratio and angle of repose before being punched as tablets. Various formulations of extended release matrix tablets of zidovudine were prepared by different ratios of HPMC and isabgol by direct compression method. The tablets were evaluated for physical characterization. From in-vitro dissolution studies all the formulations were analyzed for the drug release kinetics. When treated with the first order, zero order kinetics, and Higuchi model it was observed that all the formulations followed first order kinetics. It was shown that F5 and F6 only 85% drug release in 24 hr. In a Higuchi model (T1 to F4 0.99 and F5 and F6 0.98 respectively) however, the regression values were found to be low with zero-order compare with first order kinetics models. Thus, zero-order could not be applicable, only first order kinetic was applicable for F5 and F6. Form the n values for all the formulations ranged from 0.454to 0.653 indicating different release patterns viz. Fickian (n = 0.5), and case II non-Fickian release (0.5? n ? 0.89), Based on the diffusion control studies, it was observed that the T1 (n= 0.454), F3 (n= 0.472), F4 (n= 0.481) and F6 (n= 0.466) tablets underwent case I Fickian diffusion control, during the dissolution study. In case of Fickian release mechanism, the rate of drug release is much lesser than that of polymer relaxation (swelling/erosion). So the drug release was chiefly dependent on the diffusion through the matrix. Also it was observed that the tablets T2 (n= 0.543), F1 (n= 0.592), F2 (n= 0.568), and F5 (n= 0.653) underwent non-Fickian case II diffusion control drug release mechanism. In the non-Fickian case II release, the rate of drug release is due to the combined effect of drug diffusion and polymer relaxation. Nature of release of the drug from the extended release tablets was inferred based on the correlation coefficients obtained from the plots of the kinetic models.