ABSTRACT:
Microencapsulation of the anti-viral drug acyclovir into Eudragit S100 was carried out for means of sustaining drug release and minimizing or eliminating side effects. Microspheres of the drug were successfully encapsulated at variable drug-polymer ratio, emulsifier concentration and stirring rate with the pH sensitive Eudragit S 100 polymer using the emulsion-solvent evaporation method to obtain reproducible, uniform and spherical microspheres. The size distribution of microsphere batches generally ranged from 432.5 to 583.6 µm. Scanning electron microscopy, X-ray diffractometry, differential scanning calorimetry and in vitro dissolution studies were performed to characterize the microspheres. Scanning electron microscopy was used to identify the microsphere shape. In vitro dissolution studies were carried out on the microspheres at 37ºC (0.5±ºC) at 100 rpm with USP Dissolution Apparatus I at two successive different pH media (1.2 and 7.4). The microspheres exhibited an initial rapid release in the acidic medium and the drug release was sustained for at pH 7.4. Drug release rate kinetics followed a Higuchi spherical matrix model for microsphere preparation.