The overall objective of this study was to develop a oral sustained release metformin hydrochloride tablet by using lipophilic waxes like Hydrogenated castor oil (HCO) and stearic acid(SA), alone or in combination using different diluents such as lactose, dicalcium phosphate and microcrystalline cellulose. Metformin hydrochloride has relatively short plasma half life, low absolute bioavailability. The need for the administration two to three times a day when larger doses are required can decrease patient compliance. Sustained release formulation that would maintain plasma level for 8-12 h might be sufficient for daily dosing of metformin. The tablets were subjected to thickness, weight variation test, drug content, hardness, friability. The in vitro dissolution study was carried out using USP 22 apparatus 2, paddle method. The drug release study revealed that HCO sustain the drug release more than that of SA. Combining HCO with SA sustained the drug release (75.69 ±0.76%) more than that of the HCO and SA for 12 h. At the same wax concentration, drug release from tablets decreased in order of Lactose > Microcrystalline cellulose > Di Calcium phosphate as diluents. Kinetic modeling of in vitro dissolution profiles revealed the drug release mechanism ranges from diffusion controlled or Fickian transport to anomalous type or non-Fickian transport.
