Quinidine photosensitivity.

Photodermatitis occurring in three patients taking oral quinidine sulfate cleared when the drug was discontinued and recurred when it was readministered. The dermatitis was experimentally reproduced with long-wave ultraviolet light (UV-A, 320-400 nm) in these three patients, who also exhibited a decreased minimal erythema dose (MED) to hot quartz irradiation. Patients taking quinidine who had no dermatitis exhibited normal MEDs and normal response to UV-A. Normal subjects injected intradermally with quinidine and irradiated with UV-A showed no reaction. These observations indicate that the photosensitive dermatitis to quinidine that occurred in the three patients is idiosyncratic and that the UV-A is at least partially responsible for the development of the dermatitis that correlates with the absorption of quinidine in the UV-A range. Quinidine must be considered among the drugs that can produce photosensitive dermatitis.