Independent release behavior of Glipizide matrix release tablets containing chitosan and xanthan gum

The aim of this study was to investigate the influence of pH, buffer species and ionic strength on the release mechanism of Glipizide (G) from matrix tablets containing chitosan and xanthan gum prepared by a hot-melt extrusion process. The release mechanisms were controlled by the solubility and ionic properties of the polymers. All directly compressed (DC) tablets prepared in this study also exhibited pH and buffer species dependent release. In contrast, the HME tablets containing both chitosan and xanthan gum exhibited pH and buffer species independent sustained release. When placed in 0.1N HCl, the HME tablets formed a hydrogel that functioned to retard drug release in subsequent pH 6.8 and 7.4 phosphate buffers even when media contained high ionic strength, whereas tablets without chitosan did not form a hydrogel to retard drug release in 0.1N HCl.