Formulation and Evaluation of Gastro Retentive Matrix Tablets of Sitagliptin

The present investigation concerns the formulation and evaluation of gastro retentive matrix tablets of sitagliptin which after oral administration, are designed to prolong the gastric residence time, increase drug bioavailability and sustain the drug release. The tablets were prepared by using various polymers viz; HPMC (K4M, K15 M, K100M), xanthan gum and combination of polymers and sodium bicarbonate. The tablets were prepared by wet granulation method and further evaluated for pre compression parameters, physical characteristics, in vitro release, buoyancy time, lag-time and swelling index. Formulations were evaluated for in vitro buoyancy and drug release study using United States Pharmacopeia (USP) 23 paddle-type dissolution apparatus using 0.1 N HCl (pH 1.2) as a dissolution medium. All formulations had floating lag times below 3 minutes and constantly floated on dissolution medium for more than 12 hrs. The optimized formulations (F13) were subjected to various kinetic release investigations and it was found that the mechanism of drug release was predominantly diffusion in combination with polymeric relaxation. The best formulation (F13) remained buoyant and showed a sustained drug release (98%) for 12hrs. F13 showed no significant change in physical appearance, drug content or floating lag time after storage at 45°C/75% RH for three months.