Formulation Development and in Vitro Evaluation of Metoprolol Succinate Extended Release Matrix Tablets by Optimizing Hydrophilic Polymers

Metoprolol Succinate extended release matrix tablet was formulated for the treatment of hypertension by direct compression method using hydrophilic polymers. Formulations F1-F6 were developed using HPMC K4M&K15M; F7-F12 were developed using HPMC K15M&K100M and F12 (A-D) for optimization. The physicochemical and in-vitro release characteristics of all the formulations were investigated and compared. In Preformulation studies physicochemical interaction between the drug and excipients were determined by using FTIR. Pre-compression properties of all formulations indicated good flow and compression properties (angle of repose&360;30°, Compressibility index <17% and Hausner ratio <1.25). Post-compression properties like weight variation, friability, Drug content (between 90-110%) for all batches was within USP limits. Among all batches, F12B release pattern conform to USP specification for extended release drug delivery systems and when compared with innovator product, its similarity factor (f₂=95.23) indicates the best optimized formulation. It can be concluded that desired extended release of hydrophilic drug is also viable with hydrophilic polymer alone. F12B dissolution data was applied to various model fitting kinetic equations like Zero-order, First order, Higuchi and Korsmeyer-Peppas. Correlation coefficent (r² =0.9989) and diffusion release exponent (n=0.5865) confirmed that anomolous (non-fickian) diffusion was the main drug release mechanism.