Benoxaprofen photosensitization of cell membrane disruption

Benoxaprofen (BXP) is a nonsteroidal anti-inflammatory drug which causes cutaneous phototoxicity. Because the in vivo phototoxicity may involve photosensitized damage to mast cell membranes, the mechanism for photosensitized damage was studied in a single model system, the red blood cell. Oxygen-dependent and oxygen-independent mechanisms for membrane disruption were detected. Oxygen-dependent lysis was not quenched by superoxide dismutase and was quenched only at high sodium azide concentrations. A two-step mechanism is proposed involving initial photodecarboxylation of BXP to form a lipophilic photoproduct which subsequently photosensitizes membrane damage. Human serum albumin at 0.03% totally inhibited BXP-photosensitized lysis.