An investigation into the release of cefuroxime axetil from taste-masked stearic acid microspheres - Part 1: The influence of the dissolution medium on the drug release profile and the physical integrity of the microspheres

The dissolution properties of stearic acid-coated cefuroxime axetil (SACA) systems have been studied with a view to investigating the effects of the d issolution medium on both the release rate and the physical integrity of th e microspheres. The release from the spheres was found to be highly depende nt on the media used, with systems in distilled water (pH 6.8) and pH 5.9 S orensens modified buffer showing a relatively slow release which exhibited linearity with the square root of time, implying a diffusion process. The r ate of release from systems in pH 7.0 and 8.0 buffer was considerably faste r and did not follow simple diffusion kinetics. Examination of the microsph eres after immersion in the various media indicated a change in the integri ty of the spheres in those media which showed the most rapid release. This was particularly marked when the systems were dried in buffer, with disinte gration seen in the higher pH systems. It is suggested that the release of the drug is dependent both on diffusion through the intact microspheres and changes in the physical integrity of the spheres as a result of a reaction with the surrounding medium. (C) 1999 Elsevier Science B.V. All rights res erved.