Solar simulator-induced herpes simplex labialis: use in evaluating treatment with acyclovir plus 348U87

Models of UV radiation induced herpes labialis utilizing crude light sources have previously been used to examine the efficacy of antivirals. We sought to improve upon this model by using a solar simulator. Initial studies revealed that 13 of 34 (38%) subjects with a history of recurrent HSV labialis receiving three minimal erythema doses (MED's) of UV light developed herpes labialis. We next evaluated the effects of combined therapy with topical ACV and 348U87, a ribonucleotide reductase inhibitor, begun immediately after UV exposure for the prevention and treatment of herpes labialis. No significant reduction in the incidence or severity of herpes labialis was detected although the study was terminated after the interim analysis revealed no benefit, thus reducing the power to detect a difference. This lack of effect may be explained by the general poor efficacy of topical treatment for recurrent HSV infection. Further studies of ACV + 348U87 in vehicles that should increase the penetration and stability of the drugs are planned.