Clinical Pharmacology & Biopharmaceutics
Open Access

Abstract

Extended release matrix tablets of poorly soluble diclofenac sodium and highly soluble metformin hydrochloride were formulated by direct compression employing cashew gum, xanthan gum and hydroxyl propyl methyl cellulose as release retardants. Cashew gum was extracted from the stem bark of Anacardium occidentale L. and its suitability as a direct compression excipient was evaluated using the SeDeM Diagram Expert System. Thirteen diclofenac sodium and metformin hydrochloride tablet formulations were prepared with varying amounts of the release retardants by direct compression. Flow properties of blended powder formulations and the uniformity of weight, crushing strength, friability, swelling index and drug content of the compressed tablets were evaluated. In vitro drug release of the matrix tablets was determined in phosphate buffer (diclofenac: pH 7.4; metformin: pH 6.8) and the kinetics of drug release was determined by fitting the release data to five kinetic models. Cashew gum was determined to be a suitable direct compression excipient with a good compressibility index (ICG) value of 5.173. Diclofenac and metformin tablets produced exhibited fairly good physical properties. Tablet swelling and drug release in phosphate buffer was dependent on the type and amount of release retarding polymer used and solubility of the drug. Extended release of diclofenac (24 h) and metformin (8-12 h) from the matrix tablets in aqueous medium was achieved. Drug release from diclofenac tablets fitted zero order, first order or Higuchi model while release from metformin tablets followed Higuchi or Hixson-Crowell model. The mechanism of release of the two drugs was mostly through Fickian diffusion and anomalous non-Fickian diffusion.

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