Acyclovir-containing liposomes for potential ocular delivery. Corneal penetration and absorption

The in vitro corneal penetration and in vivo corneal absorption of acyclovir from an acyclovir-containing liposome system were investigated. Results of in vitro corneal penetration demonstrated that positively charged liposomes resulted in a penetration rate lower than those of negatively charged liposomes and free acyclovir in solution. An in vivo study indicated that the extent of acyclovir absorption from positively charged liposomes was higher that those from negatively charged liposomes and free acyclovir. The acyclovir concentration in the cornea after administration of positively charged liposomes showed that an acyclovir deposition in the cornea was greater than those of negatively charged liposomes and free acyclovir. From morphological observation of the cornea surface treated with liposomes, it was suggested that positively charged liposomes formed a completely coated layer on the cornea surface. These liposomes would bind intimately on the cornea surface, leading to an increase of residence time. Therefore, positively charged liposomes resulted in an increase of acyclovir (ACV) absorption.