Design and in vitro Evaluation of Sustained Release Dosage Forms

Metformin matrix and gastro retentive tablets formulations were prepared with different compositions. Finally, one optimized formula for each, matrix and gastro retentive, were selected and studied in detail. The effect of formulation variables namely, process of manufacturing, different excipients, different polymers, and concentration of polymer were studied. Metformin release was inversely proportional to the polymer concentration. Drug release from the developed formulations was independent of pH of the release medium but dependent on the agitational intensity, hardness of tablet, and surface area of tablet. Metformin release from both developed matrix and gastro retentive formulations follows first order. The manufacturing procedure was found to be reproducible and formulations were stable after one month of accelerated stability studies.