9. Formulation and evaluation of glipizide sustained release tablets

The objective of the present investigation was to develop a sustained release (SR) tablet formulation of glipizide by employing two hydrophobic polymers (ethyl cellulose and ethylene vinyl acetate copolymer) and two natural hydrophilic gum resins olibanum resin and colophony). Different batches of glipizide sustained release tablets were prepared by using lactose and dicalcium phosphate as diluents by wet granulation technique. The prepared tablets were evaluated for various parameters. In vitro drug release study was carried out and compared with the commercial Glynase XL tablets. The independent model method, Lin Ju and Liaw’s difference factor ( 1) and similarity factor ( 2) were used to compare various dissolution profiles. The dissolution profiles of an ideal formulation (SR F3) containing olibanum resin and lactose as diluent was found to be comparable with the reference product. The kinetics of drug release was best explained by Korsmeyer and peppas model and the mechanism of drug release from these tablets was by non-fickian diffusion mechanism. The ideal formulation (SR F3) was stable when it was stored at 4±2°C, 27±2°C and 45±2°C for 6 months. In conclusion, SR formulation of Glipizide could be developed employing olibanum resin as rate-controlling matrix former and lactose as diluent.