BIOADHESIVE MICROSPHERES FOR OPHTHALMIC ADMINISTRATION OF ACYCLOVIR

The bioavailability of acyclovir to the ophthalmic epithelium is low a nd when the drug is administered in ophthalmic ointment it must be app lied every four hours. An emulsification technique has been used to pr epare acyclovir-loaded chitosan microspheres with the aim of promoting the prolonged release of drug and increasing its ocular bioavailabili ty. The microparticulate drug-delivery systems obtained have been char acterized for their morphology and physicochemical characteristics by in-vitro dissolution tests and in-vivo ocular administration to rabbit s. The results show that the microspheres obtained are always quite sm all-the diameters of 90% of the particles are less than or equal to 25 mu m (i.e. d(90%) never exceeds 25 mu m) and physicochemical characte rization shows that the drug is homogeneously dispersed in an amorphou s state inside the microspheres. The in-vitro dissolution profile of a cyclovir from chitosan microspheres is slower than that for the raw dr ug. Results from in-vivo ocular administration of acyclovir-loaded mic rospheres to the rabbit eye show prolonged high concentrations of acyc lovir and increased AUC values. The microparticulate drug-carrier seem s a promising means of topical administration of acyclovir to the eye.