Efficacies of topical formulations of foscarnet and acyclovir and of 5-percent acyclovir ointment (Zovirax) in a murine model of cutaneous herpes simplex virus type 1 infection

The topical efficacies of foscarnet and acyclovir incorporated into a polyo xypropylene-polyoxyethylene polymer were evaluated and compared to that of 5% acyclovir ointment (Zovirax) by use of a murine model of cutaneous herpe s simplex virus type 1 infection. All three treatments given three times da ily for 4 days and initiated 24 h after infection prevented the development of the zosteriform rash in mice. The acyclovir formulation and the acyclov ir ointment reduced the virus titers below detectable levels in skin sample s from the majority of mite, whereas the foscarnet formulation has less of an antiviral effect. Reducing the number of treatments to a single applicat ion given 24 h postinfection resulted in a significantly higher efficacy of the formulation of acyclovir than of the acyclovir ointment. Acyclovir inc orporated within the polymer was also significantly more effective than the acyclovir ointment when treatment was initiated on day 5 postinfection. Th e higher efficacy of the acyclovir formulation than of the acyclovir ointme nt is attributed to the semiviscous character of the polymer, which allows better penetration of the drug into the skin.