Formulation and Evaluation of Bi-layered Matrix Tablets of Metformin and Pioglitazone for Biphasic Drug Release

The aim of the present study was to design the concept of bilayered matrix tablets containing Pioglitazone hydrochloride for immediate release using Cross Povidone as super disintegrant and Metformin hydrochloride for controlled release using Carbopol 971P as matrix forming polymer. The tablets were evaluated for physicochemical properties. All the values were found to be satisfactory. In vitro release studies were carried out as per USP in pH 1.2 and phosphate buffer pH 6.8 using the USP dissolution rate test apparatus II. The release kinetics of Metformin hydrochloride was evaluated using the regression coefficient analysis. The promising formulation (F4) shows first order release kinetics and diffusion coupled with erosion was the dominant mechanism of drug release. The polymer Carbopol 971P had significant effect on the release of Metformin HCl matrix tablets (F4).Thus formulated bilayer tablets proved immediate release of Pioglitazone and Metformin HCl as controlled release over a prolonged period of 12 hours. The similarity factor of the optimized formulation (F4) was also calculated and it was found to be 57.21. This formulation had a profile similar to the reference formulation and was comparable with the marketed formulation. The stability studies and FT-IR studies were also indicating the absence of strong interactions between the components and suggesting drug-excipient compatibility in all the formulations examined.