Ciprofloxacin-induced photosensitivity: in vitro and in vivo studies.

Ciprofloxacin is one of the new series of broad-spectrum antibiotic quinolones, chemically related to nalidixic acid and which may, therefore, induce photosensitization of human skin. Three in vitro tests for phototoxicity: the destruction of histidine, killing of mouse peritoneal macrophages and inhibition of PHA-stimulated DNA synthesis in human lymphocytes have demonstrated this photosensitizing potential with UVA irradiation at an order of magnitude lower than that for nalidixic acid. The Candida albicans test and photohaemolysis were negative. Controlled irradiation monochromator phototesting of 12 subjects, before, during and after taking ciprofloxacin showed subclinical photosensitivity with significantly lowered minimal 24 h erythema doses at 335 +/- 30 nm, 365 +/- 30 nm and 400 +/- 30 nm but not at 305 +/- 5 nm or above 400 +/- 30 nm.