Influence of different grades and concentrations of hydroxypropyl methyl cellulose on the release of metformin hydrochloride

Abstract

The main purpose of this work is to investigate drug release from matrix based metformin tablets prepared from Hydroxypropyl Methyl Cellulose of different grades: HPMCK4M, HPMCK15M and HPMCK100M of varying concentrations. Metformin tablets prepared by wet granulation using 11, 15, 20, 25 and 30% concentrations of above three grades were subjected to dissolution in USP Type I apparatus at 100 rpm medium being phosphate buffer (pH 6.8). Aliquots of sample were withdrawn at 1 hr, 3 hr, 6 hr and 10 hr and percentage drug release was analyzed in UV Spectrophotometer. The formulation was then optimized on basis of Indian Pharmacopoeia 2010 and drug release was compared with the marketed sample. Compatibility study using IR and three months stability studies were also performed. The results showed that at a fixed polymer level, drug release from the higher viscosity grade, K100M was slower as compared to the lower viscosity grades, K15M and K4M. Further, increasing concentration of same grade polymer showed decreased release rate. The release retarded with increase in polymer concentration because of swelling and gelling of HPMC which resulted in slowing penetration from the matrix due to increase in diffusional path length. High viscosity grade polymer can sustain the drug release at lower concentration than that of lower grades.