Formulation and Development of Sustained Release Microspheres of Metformin Hydrochloride

Metformin hydrochloride microspheres were prepared by non-aqueous emulsification solvent evaporation method, using hydrophobic polymer i.e. ethyl cellulose and hydroxy propyl methyl cellulose K15M. Spherical microspheres having an entrapment efficiency of 80% -87% and percentage yield of 71% -90% were obtained. The effect of polymer-drug ratio, stirring speed was evaluated with respect to entrapment efficiency 80% -87% and percent yield 71% -90% was obtained. The effect of polymer-drug ratio, stirring speed was evaluated with respect to entrapment efficiency, percentage yield and in vitro drug release behavior. Visual inspection and infrared spectroscopic analysis confirmed the absence of drug-polymer interaction. Te in vitro release profile could be altered significantly by changing the drug to polymers ratio to give sustained release of drug from microspheres. The F2 factor was found to 74% compared with marketed sample. The optimized formulation M8 was kept for stability study at refrigeration temperature, room temperature and at oven temperature (40°C to 45°C) showed no significant drug interaction.