Comparison of new topical treatments for herpes labialis - Efficacy of penciclovir cream, acyclovir cream, and n-docosanol cream against experimentalcutaneous herpes simplex virus type 1 infection

Background: There are 3 new topical treatments for herpes labialis that hav e either been approved by the US Food and Drug Administration (penciclovir cream [Denavir] and n-docosanol cream [Abreva]) or recently undergone exten sive clinical evaluation (acyclovir cream). The relative efficacy of these products is unknown. Objective: To compare the efficacy of penciclovir cream, acyclovir cream, n -docosanol cream, and acyclovir ointment in an experimental animal model of cutaneous herpes simplex virus type 1 (HSV-1) disease. Design: The backs of guinea pigs were infected with HSV-1 using a vaccinati on instrument. Active treatments and corresponding vehicle controls were ap plied for 3 to 5 days beginning 24 hours after inoculation. Main Outcome Measures: After completion of treatment, the animals were kill ed and the severity of the infection assessed from the number of lesions, t he total lesion area, and the lesion virus titer. Results: Penciclovir cream effected modest reductions in lesion number (19% ), area (38%), and virus titer (88%) compared with its vehicle control, and each of these differences was significantly greater (P<.05) than the reduc tions effected by acyclovir ointment (0%, 21%, and 75%, respectively). The acyclovir cream effect (reductions of 4%, 28%, and 77%, respectively) was l ess than that of penciclovir cream, and this difference was confirmed by 2 additional head-to-head experiments, Two experiments with n-docosanol cream failed to show statistically significant differences by any parameter betw een n-docasonol cream and vehicle control-treated sites or between n-docosa nol and untreated infection sites. Conclusions: In this model, the efficacy of penciclovir cream was greater t han acyclovir cream, acyclovir cream was greater than or equal to acyclovir ointment, and acyclovir ointment was greater than n-docosanol cream. Since our model was designed to evaluate compounds that function primarily throu gh antiviral activity, the negative findings with n-docosanol in these stud ies do not exclude that it might work clinically through other mechanisms.