Phototoxicity of non-steroidal anti-inflammatory drugs: in vitro studies with visible light

Photosensitivity reactions due to non-steroidal anti-inflammatory drugs (NSAID) are well-known side-effects of these agents and are usually attributed to ultraviolet (UV) radiation. Eight NSAID (carprofen, diclofenac, ibuprofen, ketoprofen, naproxen, piroxicam, phenylbutazone, tiaprofenic acid) were assessed in a photohemolysis test for phototoxic effects in the visible light range. For the studies an experimental visible light lamp was used, emitting 5% UVA at most. To control for UVA-induced effects, additional samples were exposed to appropriate UVA doses from an UVA source and as well to the visible light lamp while being covered by a GG 400 or GG 420 filter. Photo-induced hemolysis was found after exposure to the visible light lamp with carprofen, ketoprofen, naproxen, piroxicam, phenylbutazone or tiaprofenic acid; diclofenac or ibuprofen did not cause photohemolysis. Control irradiation with UVA induced minor hemolysis only with carprofen, ketoprofen and tiaprofenic acid. When the samples were exposed to the filtered visible light lamp, using the GG 400 filter, photohemolysis was found with carprofen, naproxen and phenylbutazone and, using the GG 420 filter, with carprofen and phenylbutazone. Phototoxic effects induced by visible light may be of importance with regard to clinical photosensitization.