EVALUATION OF XANTHAN GUM IN THE PREPARATION OF SUSTAINED-RELEASE MATRIX TABLETS

The objective of this study was to evaluate xanthan gum as a matrix fo rmer for the preparation of sustained release tablets. Preliminary exp eriments indicated that a fine particle size of xanthan gum produced t he slowest and most reproducible release profiles. Based on single sur face experiments and tablet erosion studies, it was concluded that rel ease of a soluble drug (chlorpheniramine maleate) and an insoluble dru g (theophylline) from tablets containing low concentraions of xanthan gum was mainly via diffusion and erosion, respectively. Drug release f rom tablets containing xanthan gum was slightly faster in acidic media due to more rapid initial surface erosion than at higher pH. After hy dration of the gum, drug release was essentially pH-independent. The a mount released was directly proportional to the loading dose of drug a nd inversely proportional to gum concentration in tablets. Release pro files of chlorpheniramine maleate and theophylline remained unchanged after three months storage of the tablets at 40-degrees-C/80% RH and 4 0-degrees-C. Model tablets containing 5% xanthan gum exhibited release profiles similar to tablets containing 15% hydroxypropyl methylcellul ose.