Formulation and Evaluation of Bilayer Tablets of Metformin Hydrochloride

The objective of the work was to design a controlled release oral dosage form of metformin bilayer tablet. In this formulation the loading dose was incorporated in the immediate release layer so that the minimum effective concentration may be attained within a shorter period of time after this the maintenance dose level will be taken over by the drug release from the second layer of the bilayer tablet. Patient convenience is improved because fewer daily doses are required compared to traditional delivery system.The Bilayer tablets of Metformin HCL were prepared by direct compression method. F10 is considered to be the optimized formulation with the desired drug release. The polymers which have been used in the best formulation (F10) are HPMC K4M and SCMC, Starch, Croscarmelose sodium, Crospovidone. The granules were evaluated for angle of repose, bulk density, tapped density, compressibility index, hausner’s ratio and moisture content. The tablets were subjected to weight variation, thickness, hardness, friability, drug content and invitro release studies. The results of FTIR analysis of pure drug, drug – excipients mixtures and tablet formulations showed that there was no physical and chemical interaction of drug with the other excipients.The stability studies of optimized formulation F10 at 25oC/60 % RH, 30oC / 75% RH, 40oC/75% RH for 3 months did not show any variation in the tested parameters and release also. The TG/DTA analysis reveals that there is a weak intermolecular interaction between drug and excipients. The phenomenon of drug release shown that the release of optimized formulation F10 is controlled by swelling mediated diffusion. By using the sustained release dosage form incidents of both local and systemic adverse effect can be reduced.