[Incidence of drug-induced photosensitization during phototherapy]

Exogenous photosensitization represents one of the adverse effects of phototherapy. However, the impact of potentially photosensitizing drugs on the incidence of photo-induced eruptions during phototherapy is unknown.

To determine the incidence of drug photosensitization during phototherapy.

This was a retrospective study of all patients undergoing phototherapy between November 1999 and April 2004 in the Dermatology Department of Caen University Teaching Hospital. Details of all topical or systemic medications taken before or during phototherapy were recorded. Since methoxsalen induces photosensitization, sessions of phototherapy were stratified according to whether methoxsalen was given. Screening was performed for the following clinical signs of drug photosensitization: acute photo-induced, erythematous and/or vesicular eruption, associated with pruritus or burning.

In the non-methoxsalen group, use of a potentially photosensitizing drug was found for 29/155 TL01 phototherapy sessions. Drug-induced photosensitization was suspected in 3/29 sessions (10.3%). In the methoxsalen group, a potentially photosensitizing drug was found in 21/118 sessions of PUVA-therapy. Drug-induced photosensitization was suspected in 4/21 sessions (19%). Risk of photo-induced eruption was not associated with photosensitizing drug therapy, TL01 phototherapy or PUVA-therapy.

Drug photosensitization appears to be rare during phototherapy, regardless of photosensitizing drug intake. It is twice as frequent during PUVA-therapy as during TL01 phototherapy but this difference is not significant.