Microemulsion-based hydrogel formulation of penciclovir for topical delivery.

The purpose of this study was to investigate microemulsion-based hydrogel (MBH) as a topical delivery system for penciclovir. Topical delivery of penciclovir in the forms of microemulsion, MBH and the commercial cream was evaluated in vitro and in vivo. The results of permeation test in vivo in mice showed that compared with the commercial cream, MBH and microemulsion could significantly increase the permeation of penciclovir into both epidermis and dermis. Stability test showed that MBH stored at 4 degrees C for 3 months had no significant change in physicochemical properties. Skin irritation test in rabbit demonstrated that single application or multiple applications of MBH did not cause any erythema or edema, slight skin irritation for microemulsion. Microstructure changes of skins after administration observed under light microscope and scanning electron microscope (SEM) might result from the interaction of the ingredients of microemulsion with skins, which was related with the permeation enhancement of penciclovir. It can be concluded that the MBH could be a promising vehicle for topical delivery of penciclovir.