Efficacy and safety of foscarnet for recurrent orolabial herpes: a multicentre randomized double-blind study.

Foscarnet sodium (trisodium phosphonoformate hexahydrate) has been shown to inhibit herpes simplex virus (HSV) in vitro and to be efficacious for topical treatment of experimental HSV infection in animals. To assess its clinical efficacy in the treatment of recurrent orolabial herpes a multicentre collaborative, double-blind, placebo-controlled trial was conducted. The study patients were randomly assigned to receive either 3% foscarnet cream (78 patients) or placebo (cream vehicle) (75 patients) and were asked to start treatment at the earliest indication of a recurrence. Efficacy was evaluated in 143 patients (74 in the foscarnet group and 69 in the placebo group). There was no significant difference in time to healing or duration of virus shedding between the two groups. However, in the subgroup of patients who started treatment before vesicles appeared, the duration of virus shedding was shorter in the foscarnet group than in the placebo group (p = 0.04), and the proportion of lesions that evolved to the vesicular stage was smaller (p = 0.03). No significant difference in the incidence of local or systemic adverse effects was noted between the two groups. We conclude that the beneficial effect of foscarnet was limited to a subgroup of patients who started treatment in the prevesicular stage.