Demonstration of olaquindox phototoxicity in vitro.

Olaquindox is an oral anti-bacterial agent used as an additive to animal food. It is known to cause photosensitization in pig breeders, probably due to a photoallergic mechanism. Also, olaquindox was found to be phototoxic in animal experiments. We have evaluated the phototoxic properties of olaquindox in vitro with a photohemolysis test using different light sources. Irradiation with a source rich in ultraviolet A (UVA) and, to a lesser degree, with a lamp emitting mainly visible light induced photohemolysis, which depended on the concentration of olaquindox and the radiation dose. Exposure to radiation rich in UVB caused no olaquindox-dependent hemolysis. The absorption spectrum of olaquindox changed prominently after irradiation, indicating photodegradation of the compound.