PREPARATION OF BIODEGRADABLE MICROCAPSULES OF ZIDOVUDINE USING SOLVENT EVAPORATION - EFFECT OF THE MODIFICATION OF AQUEOUS-PHASE

The objective of the present investigation was to improve the efficien cy of encapsulation of zidovudine (AZT) in poly(lactide/gycolide) (PLG A 50:50) by modifying the secondary aqueous phase. Surface morphology of the microcapsules was unchanged during the partial saturation of th e aqueous phase with calcium chloride, However, partial saturation of the aqueous phase with AZT and a change in the pH of the aqueous phase showed significant effect on the surface morphology. The surface appe ared to be wrinkled when the pH of the aqueous phase was adjusted to 1 0. The particle size was between 8 and 18 mu m. The particle size was increased significantly (78 - 140 mu m) when the aqueous phase was par tially saturated with AZT (0.25 - 0.75%). The efficiency of encapsulat ion did not change when the aqueous phase was partially saturated with calcium chloride (5 - 30%). The efficiency of encapsulation was pH de pendent. The encapsulation increased up to 17% when the aqueous phase was partially saturated with 0.75% AZT. The cumulative drug release fr om the microcapsules was between 15 and 34% within the first 24 h. A s ustained drug release continued up to 60 days.