Phototoxicity of non-steroidal anti-inflammatory drugs demonstrated in vitro by a photo-basophil-histamine-release test.

The phototoxic activity of the non-steroidal anti-inflammatory drugs (NSAID) acetylsalicylic acid, benoxaprofen, carprofen, diclofenac, indoprofen, ketoprofen, tiaprofenic acid, and of thiophene, a heterocyclic ring structure of the tiaprofenic acid molecule, was evaluated in vitro by a newly developed photo-basophil-histamine-release test (PBHRT) performed with human leukocytes. Cell suspensions incubated with 10(-6) to 10(-3) M of the test compounds were exposed to 1 to 100 J/cm2 UVA. Maximum photo-basophil-histamine-release was 4% with acetylsalicylic acid, 10% with benoxaprofen, 20% with thiophene, 28% with diclofenac, 39% with tiaprofenic acid, 40% with carprofen, 55% with ketoprofen, and not demonstrable with indoprofen. These results indicate that many NSAID can exert phototoxic effects, thus confirming clinical observations as well as other in vitro experiments. The PBHRT seems to be a promising new method for the identification of phototoxic compounds.