Determining therapeutic efficacy in recurrent herpes labialis by lesion size analysis

We devised an experimental model for the analysis of therapeutic efficacy of topical medications for recurrent herpes labialis with a double-blind, placebo-controlled format. Rigid prestudy screening evaluations allowed the enrollment of a homogeneous starting population with characteristic herpetic reactivation in an early stage. Using precise measurements of lesion area for a 5-day period, we evaluated the effects of a novel medication containing tannic acid, which has demonstrated impressive inhibitory effects on herpes simplex virus in many recent studies, and salicylic acid, which has rapid absorption kinetics and substantial topical anti-inflammatory and keratin-disrupting properties. Using parametric and nonparametric tests, we studied differences in mean lesion size and used these measurements to evaluate objective and clinically applicable improvement criteria. Although there were no significant differences in mean lesion size at presentation (day 1) between the active medication and placebo groups, the former demonstrated significantly smaller lesions at days 2 through 5 (p less than 0.05). By day 5, 10 of 14 treated subjects showed improvement as defined by a 25% reduction in lesion size compared with day 1, in contrast to only 2 of 12 subjects in the placebo group (p = 0.0079, Fisher's Exact Test). This model can be employed in the evaluation of topical antiviral agents for herpes labialis in a healthy population, because it standardizes criteria for subject enrollment and provides objective and reproducible measurements of therapeutic efficacy.