Photodynamic inactivation in recurrent infections with herpes simplex virus.

Photodynamic inactivation with neutral red (a heterotricyclic dye) and light was evaluated in a placebo-controlled study of 170 episodes of recurrent infection with herpes simplex virus in 96 patients. The technique inactivated herpes simplex virus in vitro. However, no beneficial effect, either on the rate of resolution of herpetic lesions or on the interval to subsequent recurrences, was observed in treated patients. These negative results should not deter further investigation of photodynamic inactivation as a potential treatment for herpes simplex virus infections, but the clinical application of this form of therapy should be limited to properly controlled studies until its efficacy is proven.