Use of Hydrophilic Natural Guar Gum in Formulation of Controlled-Release Matrix Tablets of Metformin Hydrochloride and Its Comparison with Marketed Product

In the present investigation an attempt was made to formulate the oral controlled release metformin hydrochloride matrix tablets by using Guar gum as rate controlling polymer and to evaluate drug release parameters as per various release kinetic models. The tablets were prepared by wet granulation method. Granules were prepared and evaluated for loose bulk density, tapped density, compressibility index and angle of repose, shows satisfactory results. All the granules were lubricated and compressed using 12.8 mm flat faced punches. Compressed tablets were evaluated for uniformity of weight, content of active ingredient, friability, hardness, in vitro release studies and swelling index. All the formulations showed compliance with Pharmacopoeial standards. The in vitro dissolution study was carried out for 12 hours using paddle (USP type II) method in phosphate buffer (pH 6.8) as dissolution media. The prepared matrix tablets were shown 99.92%, 97.41%, 94.95%, 89.29%, 86.41% and 84.72% release over a period of 12 hours. Formulations F-1 and F-2 failed to sustain release beyond 9 hours and 11 hours, respectively. Among all the formulations, F-5 showed the controlled release of drug for 12 hours with 86.41% release and the release profile was close to the marketed sample of metformin hydrochloride (M-SR). Selected formulation (F-5) was subjected to stability studies for 3 months, which showed stability with respect to release pattern. The drug release follows first order kinetics and the mechanism was found to be diffusion coupled with erosion.