Evaluation of Xanthan Gum in the Preparation of Sustained Release Matrix Tablets

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Abstract
The objective of this study was to evaluate xanthan gum as a matrix former for the preparation of sustained release tablets. Preliminary experiments indicated that a fine particle sue of xanthan gum produced the slowest and most reproducible release profiles. Based on single surface experiments and tablet erosion studies, it was concluded that release of a soluble drug (chlorpheniramine maleate) and an insoluble drug (theophylline) from tablets containing low concentraions of xanthan gum was mainly via diffusion and erosion, respectively. Drug release from tablets containing xanthan gum was slightly faster in acidic media due to more rapid initial surface erosion than at higher pH. After hydration of the gum, drug release was essentially pH-independent. The amount released was directly proportional to the loading dose of drug and inversely proportional to gum concentration in tablets. Release profiles of chlorpheniramine maleate and theophylline remained unchanged after three months storage of the tablets at 40°C/80% RH and 40°C. Model tablets containing 5% xanthan gum exhibited release profiles similar to tablets containing 15% hydroxypropyl methylcellulose.