Formulation and Evaluation of Gastroretentive Bilayer Tablets

Gastroretentive bilayer tablets were designed to prolong the gastric residence time after oral administration and to achieve immediate release of lansoprazole and controlled release floating layer of clarithromycin to treat gastric ulcers. Instant release layer has a combination of super disintegrating agents. A combination of effervescent mechanism is used. HPMC K5 was used as swelling polymer and citric acid, sodium bicarbonate as gas generating agent to reduce the floating lag time. Bilayer floating tablets were prepared with varying proportions of instant layer and sustained release floating approaches. The prepared formulations were evaluated for various tablet and floating parameters. Tablet properties were found to be within the limits according to procedures prescribed in USP. They had a floating lag time around 3-7 seconds and floating time more than 24 hours. The cumulative % drug release in simulated gastric fluids after 10 hours was 70% - 95%. The mechanism of drug release was analyzed by fitting the release data into various kinetic models. It was found that all the formulations best fit the Higuchi’s model. Keywords: Gastroretentive drug delivery system; Bilayer tables, Instant release layer, Floating layer, Lansoprazole, Clarithromycin.