The study by McKeough and Spruance1 in this issue of the ARCHIVES demonstrates the relative efficacy of 4 topical antiviral agents for the treatment of herpes simplex virus type 1 (HSV-1) infection using the backs of guinea pigs. Efficacy was measured by reductions in lesion number, area, and virus titer. They found, in this model, that the relative efficacy of penciclovir cream was greater than acyclovir cream, acyclovir cream was greater than or equal to acyclovir ointment, and acyclovir ointment was greater than n-docosanol cream. A clinical study comparing all 4 agents would be very expensive and is unlikely ever to be done. The authors note, however, that the guinea pig model is twice as sensitive to antiviral therapies as is herpes labialis. It is therefore interesting that the relative efficacies in the animal model closely reflect the perception of many physicians regarding the efficacy of these agents in herpes labialis. Compared with its vehicle, penciclovir appears to have the greatest clinical benefit for herpes labialis. Because HSV-1 infection is primarily neural and not cutaneous, it is logical that oral antiviral drugs would be more beneficial than topical agents. A small amount of literature exists for oral acyclovir, but paradoxically very little information exists regarding the efficacy of the newer nucleoside analogues, famciclovir and valacyclovir hydrochloride, in the therapy of herpes labialis. Therefore, more studies are needed on these oral agents and drugs with different mechanisms of action, such as the immune response modifier resiquimod.
Vander Straten M, Carrasco D, Lee P, Tyring SK. A Review of Antiviral Therapy for Herpes Labialis. Arch Dermatol. 2001;137(9):1232-1235. doi:10.1001/archderm.137.9.1232