Rapid Decrease of Phototoxicity After PUVA Bath Therapy With 8-Methoxypsoralen

PUVA bath therapy has distinct advantages compared with systemic PUVA therapy, eg, lack of systemic side effects and better bioavailability of psoralen.1-6However, one astonishing drawback of the PUVA bath procedure is the lack of study-generated guidelines for the realization of the procedure. Therefore, we conducted 2 studies to determine the optimal time for irradiation and for how long photosensitivity persists after the bath. The biological activity of 8-methoxypsoralen (8-MOP) was evaluated by determination of the minimal phototoxicity dose (MPD). In a previous study7on PUVA bath phototoxicity, we demonstrate that irradiation immediately and 20 minutes after the bath induces a relatively uniform ).ototoxic response with low UV-A doses (0.5-1.0 J/cm2). Thereafter, a rapid increase of the MPD occurred, thus indicating a decrease of drug activity.7The aim of the present study was to evaluate the photosensitivity up to 4 hours after PUVA bath. Materials and Methods. Six