FORMULATION AND EVALUATION OF SUSTAINED RELEASE TABLETS OF MEFENAMIC ACID USING HYDROPHOBIC POLYMERS

Abstract

Mefenamic acid is a non-steroidal anti-inflammatory drug used to treat pain, including menstrual pain. It has a dose of 250 mg 4 times daily. It has a very short half life of 2 hours and thus controlling the release would be beneficial. In the present study, mefenamic acid 250 mg controlled release matrices were prepared by direct compression and in-vitro drug dissolution studies were performed to find out the drug release rate and patterns. Ethyl cellulose (EC), polyvinyl acetate (PVA) and their combination were used as rate controlling polymers. Effects of addition of ethyl cellulose and polyvinyl acetate on in-vitro drug dissolution were studied.  Tablets were formulated using total polymer content as 20, 30 and 40 percent. In-vitro drug release was carried out using USP Type II at 50 rpm in 900 ml of acidic dissolution medium (pH 1.2) for 2 hours, followed by 900 ml alkaline dissolution medium (pH 7.4) up to 24 hours. Mean dissolution time is used to characterize drug release rate from a dosage form and indicates the drug release retarding efficiency of polymer. When ethyl cellulose and polyvinyl acetate were used alone as the only retarding polymer, retardation effect increased proportionately as the concentration of polymer increased; however lacked the uniform release profile and desirable physical properties. Combination in the matrix gave both the uniform retardation effect as well as desired physical properties to the formulation. Several kinetic models were applied to the dissolution profiles to determine the drug release kinetics.

KEYWORDS: Mefenamic acid , Ethyl cellulose, Polyvinyl Acetate, Release Kinetics.