It can occur as a drug reaction in patients treated with tetracyclines (photo-onycholysis), doxorubicin, 5 - fluorouracil, cardiovascular drugs (particularly practolol and captopril), cloxacillin and cephaloridine (rarely), trimethoprim / sulfamethoxazole, diflunisal, etretinate, indomethacin, isoniazid, griseofulvin, and isotretinoin.