Preparation and evaluation of gastro retentive floating tablets of atorvastatin calcium

Abstract

This investigation describes the preparation and in vitro evaluation of gastro retentive floating tablets of atorvastatin calcium. Two hydrophilic cellulose derivatives, Methocel K4M and Methocel K15M CR were used in floating tablets as gel forming agents to control drug release. Sodium bicarbonate and citric acid were incorporated as gas generating agents. The tablets prepared by direct compression technique were evaluated by various quality parameters including weight variation, hardness and buoyancy studies. In vitro drug release was determined for eight hours using USP XXII paddle-type dissolution apparatus in 0.1N HCl solution containing 1% sodium lauryl sulphate. The release mechanisms were explored and explained with zero order, first order, Higuchi and Korsmeyer equations. The release rates, extent and mechanisms, were found to be governed by polymer loading. It was also found that the polymer content significantly affected the mean dissolution time, percentage of drug release, release rate constant and diffusion exponent. Based on the dissolution data and floating time, formulation F-3 containing Methocel K4M and F-9 containing Methocel K15M CR may be considered as the best formulation. So an effective floating tablet of atorvastatin calcium can be prepared by using both the grades of HPMC.