Polysaccharide gum matrix tablets for oral controlled delivery of cimetidine

Matrix-based tablets using 40%w/w grewia gum were prepared by direct compression to contain cimetidine as novel drug. The formulations were compared with similar formulations using hydroxypropyl methylcelluose (Methocel^®), gum arabic, carboxy methylcellulose (Blanose^®), or ethyl cellulose (Ethocel^®) as polymer matrix. Also binary composite matrices containing grewia gum and the reference polymers (40%w/w total polymer concentration in a ratio of 1:1) were directly compressed. In addition to tablet properties, swelling, erosion, kinetics of drug release from the matrices and stability of the tablet formulations were also investigated. In vitro drug release studies reveal that grewia gum can control the release of cimetidine from tablets for up to 12 hours. This strong sustained-release potential of grewia polysaccharide gum was superior to hydrophilic matrices of hydroxypropyl methylcellulose, carboxy methylcellulose and gum arabic. The release of drug from the grewia polysaccharide gum matrices follows Higuchi kinetic models. There was synergy between grewia gum and HPMC in delaying the release of cimetidine from tablets. Grewia gum may therefore prove a useful excipient when used alone, or in combination with other polymers to modify the release of soluble drugs from polymeric matrices.