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