In a double-blind, randomized, patient-initiated clinical trial, 174 nonimmunocompromised patients with a history of virus-culture-confirmed herpes simplex labialis were treated with acyclovir capsules, 400 mg five times daily for 5 days, or placebo capsules. For 97% of the patients, treatment started within 1 h of the first sign or symptom of a recurrence. The frequency of positive lesion virus cultures was significantly lower among acyclovir-treated subjects (29/114, 25%) than among placebo-treated subjects (29/60, 48%; P = .004). Drug treatment did not affect the development of lesions, measured by the frequency of macular and papular (aborted) lesions and mean maximum lesion size. However, acyclovir hastened lesion resolution among the patients who could start treatment in the prodrome or erythema lesion stage. For this group, the mean duration of pain was reduced by 36% (P = .02) and the mean healing time to loss of crust by 27% (P = .03). Thus, oral acyclovir alleviated some of the clinical manifestations of herpes simplex labialis.

The lips of 196 patients with a history of sun-induced herpes labialis were exposed to experimental ultraviolet radiation (UVR) and treated with acyclovir (ACV) or placebo at different times and by different routes. Of 98 placebo recipients, 39 (40%) developed 43 lesions inside or within 10 mm of the irradiated zone. The temporal distribution of lesions was bimodal. 11 (26%) occurring within 48 h (immediate) and 32 (72%) 2-7 days after UVR exposure (delayed). Prophylactic peroral ACV begun 7 days before or 5 min after UVR prevented the development of the delayed but not the immediate lesions (P less than .001). When peroral ACV was started 48 h after UVR, delayed lesions developed but were less severe (P = .01-.05). Prophylactic topical ACV begun 5 min after UVR did not reduce lesion frequency or severity. ACV therapy can be efficacious, but some rapidly developing lesions are unresponsive to treatment. This suggests that more than one process may contribute to the pathogenesis of herpes labialis.

Three doses of famciclovir were tested for treatment of experimental ultraviolet radiation (UVR)-induced herpes labialis. Patients received 125, 250, or 500 mg of famciclovir or placebo 3 times a day for 5 days beginning 48 h after UVR exposure, a model of early episodic intervention. Of 248 patients irradiated, 102 developed lesions while on treatment. There were no significant differences between groups in the number of lesions. The mean maximal lesion size was reduced in a dose-proportional manner: 139, 105, 77, and 55 mm2 for the placebo and 125-, 250-, and 500-mg famciclovir groups, respectively (P=.040, linear regression). Median time to healing was faster in the 500-mg famciclovir group than in the placebo group, both by investigator (4 vs. 6 days, 33% reduction, P=.010) and patient assessment (3.0 vs. 5.8 days, 48% reduction, P=.008) analyses. These findings suggest that evaluation of higher drug doses for herpes labialis treatment is warranted.