An investigation into the release of cefuroxime axetil from taste-masked stearic acid microspheres. II. The effects of buffer composition on drug release

The influence of buffer composition on the release of cefuroxime axetil fro m stearic acid microspheres has been investigated, with particular emphasis on establishing the relationship between buffer composition and release at a single pH value. Studies of drug dissolution and release from spheres in pH 7.0 citrate phosphate buffer (CPB), boric acid buffer (BAB), phosphate buffer mixed (PBM) and Sorensens modified phosphate buffer (SMPB) indicated marked differences in release profile from the spheres, with an approximat e rank order of SMPB > CPB approximate to BAB > PBM. The role of added sodi um was then investigated by examining the release profiles in SMPB and PBM to which sodium ions had been added. Increases in the sodium content from a pproximate to 0.11 to 0.2 M were found to decrease the release rate for the SMPB, while increases from 0.007 to 1.0 M sodium in PBM resulted in a maxi mum release being seen for the systems containing 0.05 M sodium. Studies on surface disintegration, using scanning electron microscopy (SEM) and sodiu m uptake using flame emission spectroscopy, indicated an interrelationship between medium composition, disintegration and release. The data are discus sed in terms of the possible mechanisms associated with drug release from t hese spheres. (C) 2000 Elsevier Science B.V. All rights reserved.