Experimental studies on the mechanism of benoxaprofen photoreactions

Benoxaprofen (BP), a non-steroidal antiphlogistic drug causing skin and nail photoreactions, has been evaluated for photoactivity using three experimental techniques. In vivo in the mouse, BP was phototoxic in doses of 25 mg/kg in combination with UV-A 54J. The phototoxic potency could be confirmed in vitro with the Candida albicans test. In vitro, using photohemolysis, BP showed a dose-dependent activity causing 40% hemolysis at a concentration of about 25 micrograms/ml with UV-A. Also, small UV-B doses caused red cell lysis with a moderate BP concentration. Pre-irradiation experiments showed that UV-A, but not UV-B, photoproducts could account for some of the activity. The action spectrum of BP photoactivity lies mainly in the UV-A, but may also extend into UV-B. Compared with chlorpromazine in vivo and in vitro, and with doxycycline in vivo, BP showed intermediate phototoxic activity.