Photopatch testing negative in systemic quinine phototoxicity

Drug-induced phototoxicity can be caused by topical or systemic agents and is diagnosed on the basis of clinical history, examination and appropriate investigations. Photopatch testing is the investigation of choice for topical photocontact allergic dermatitis, but its use in drug-induced phototoxicity has not been validated. We retrospectively analyzed the results of photopatch testing to the drug quinine sulfate in three patients in whom a diagnosis of drug-induced phototoxicity to this agent had been made. None of the three patients had positive photopatch test reactions at any time point. This demonstrates that in our patients, photopatch testing to quinine sulfate was not a useful additional investigation for diagnosing drug-induced phototoxicity.