Sustained Release of Metformin HCl from Hydroxy Propyl Methyl Cellulose Matrices: Formulation and in vitro Evaluation

Abstract

Sustained release formulation of metformin HCl presents significant challenges due to its poor inherent compressibility, high dose and high water solubility. Sustained release matrix tablets of metformin HCl were formulated using different grades of hydroxy propyl methyl cellulose (HPMC) (HPMC K 4 M, HPMC K 15 M and HPMC K 100 M) by non-aqueous wet granulation method. The granules were evaluated for angle of repose, bulk density, compressibility index and total porosity. The tablets were subjected to thickness, weight variation test, drug content, hardness and friability. in vitro release studies were carried out at 0.1 N HCl and phosphate buffer of pH 6.8 using the apparatus I (basket) equipment as described in the USP 24/NF dissolution monograph. The granules showed satisfactory flow properties, compressibility and drug content. There was no significant difference in drug release for different viscosity grade of HPMC with same concentration. Release kinetics was evaluated using the regression coefficient analysis. All the formulations exhibited diffusion-dominated drug release and followed Higuchi release kinetics. Tablet thus formulated provided sustained release of metformin HCl over a period of 8 h.