Formulation development, optimization, and evaluation of sustained release tablet of valacyclovir hydrochloride by combined approach of floating and swelling for better gastric retention.

The present study is intended to enhance gastric retention of sustained release tablet of valacyclovir hydrochloride by combined approach of floating and swelling. The tablets are prepared by direct compression method. Polyethylene oxide (Polyox WSR 303) is selected as the swelling matrix agent. Sodium starch glycolate (SSG) is used as swelling enhancer, and sodium bicarbonate is used as an effervescent agent for floating. A 3(2) full factorial design is applied to systematically optimize the formulation. The concentration of Polyox WSR 303 (X 1) and concentration of SSG (X 2) are selected as independent variables. The percentage drug release at 12 h, floating lag time, and maximum percentage swelling are selected as dependent variables. Formulations are evaluated for hardness, friability, floating lag time, total floating time, percentage swelling, in vitro drug release, and in vivo floating study. The results indicated that X 1 and X 2 significantly affected the drug release properties, floating lag times, and maximum percentage swelling. Release rate decreases as the concentration of Polyox increased. Regression analysis and numerical optimization are performed to identify the best formulation. Formulation F5 prepared with Polyox WSR 303 (15 %) and SSG (10 %) is found to be the best formulation. F5 followed zero-order release mechanism. Swelling and floating gastroretentive tablets of valacyclovir HCl are successfully formulated with controlled delivery to stomach with an aim of increasing the mean residence time in the upper part of GIT where the drug has its absorption window.