Formulation and Optimization of Sustained Release Matrix Tablet of Metformin HCl 500 mg Using Response Surface Methodology

The aim of the current study was to design an oral sustained release matrix tablet of metformin HCl and to optimize the drug release profile using response surface methodology. Tablets were prepared by non-aqueous wet granulation method using HPMC K 15M as matrix forming polymer. A central composite design for 2 factors at 3 levels each was employed to systematically optimize drug release profile. HPMC K 15M (X1) and PVP K 30 (X2) were taken as the independent variables. The dependent variables selected were % of drug released in 1 hr (rel1 hr), % of drug released in 8 hrs (rel8 hrs) and time to 50% drug release (t50%). Contour plots were drawn, and optimum formulations were selected by feasibility and grid searches. The formulated tablets followed Higuchi drug release kinetics and diffusion was the dominant mechanism of drug release, resulting in regulated and complete release within 8 hrs. The polymer (HPMC K 15M) and binder (PVP K 30) had significant effect on the drug release from the tablets (p