Formulation and Characterization of Metformin Hydrochloride Floating Tablets

The objective of the research work was to provide a gastroretentive system for sustained release of metformin HCl in proximal part gastrointestinal tract (GIT) in the form of oral floating tablet. Metformin HCl is an anti-diabetic biguanid with poor bioavailability and absorption window at the upper part of GIT. Floating tablets were prepared by wet granulation method incorporating natural polymers guar gum and k-Carrageen and a synthetic polymer HPMC K100 (HPMC) either alone or in combination. Sodium bicarbonate and citric acid was used as gas generating agent. Floating tablets were evaluated for weight variation, hardness, and friability, drug content, swelling index, in vitro buoyancy and in vitro drug release study. The formulation optimized based on floating ability, matrix integrity, and in vitro drug release in simulated gastric fluid pH 1.2. Formulation prepared with combination of 6% w/w k-carrageen and 11%w/w guar gum showed good gel strength, stable and persistent buoyancy for 12h, least floating lag time of 58 sec with good matrix integrity throughout dissolution period. The drug release of optimized formulation followed the Korsmeyer-Peppas model and the mechanism was non-Fickian/anomalous. PXRD and DSC studies revealed partial amorphization of drug. The mechanism of drug release was appears to be diffusion mechanism. Stability studies indicated absence of any drug degradation on storage for 3 months at 40℃. Comparison study with Glutamet^® showed that the optimized formulation has better and complete release than the marketed product. Studies revealed usefulness of natural polymers over synthetic one.