Ritesh Kumar, Amrish Chandra, Seema Garg

 In the present study hydrophilic gelling polymer based gastroretentive (floating) tablets of metformin hydrochloride were formulated and evaluated for increase bioavailability by increasing gastric residence time and sustained release of drug on the upper part of gastrointestinal tract thereby diminishing side effects and enhanced patient compliance. Metformin hydrochloride, an oral antidiabetic having narrow absorption window in the upper part of gastrointestinal tract, was formulated as floating matrix tablet using gas generating agent (potassium bicarbonate) and hydrophilic gelling polymer hydroxyl propyl methyl cellulose (hypromellose) by wet granulation technique. The formulation was optimized on the basis of in vitro drug release profile using 23 full factorial design with t50% and t80% as the kinetic parameters. The prepared formulations were evaluated for floating time and in vitro drug release characteristics using modified dissolution method. All formulations possessed good floating properties with total floating time more than 12 hours. Formulations with high amount of hypromellose were found to float for longer duration and provide more sustained release of drug. The formulated drug delivery system was found to be independent of pH. Result showed the formulation F4 to closely match the extra design checkpoint (F9) formulation with a similarity factor value of 98.13. Matrix characterization included photomicrograph, scanning electron microscopy which showed definite entrapment of drug in the matrix. Release kinetics of formulations followed Higuchi model with anomalous non fickian diffusion. Hence it is evident from this study that gastroretentive tablets could be a promising delivery system for metformin hydrochloride with sustained drug release action and improved drug bioavailability.
Keywords: Metformin; Hypromellose; Gastroretentive; Matrix.