[Side effects off allopurinol].

Allopurinol is generally considered to be a safe and well tolerated drug. We report one patient with a serious effect from allopurinol, a serious exfoliative rash and signs of allopurinol hypersensitivity syndrome. Only after considerable diagnostic delay and patient morbidity, signs and symptoms were associated with the drug. The patient recovered when the medication was withdrawn. Data from the Norwegian reporting system for side effects of drugs for the period 1973-2003 show a wide range of side effects of allopurinol and even some fatalities. The indication for treatment must be carefully considered. Impaired renal function, ampicillin and thiazide diuretics increase the risk of serious hypersensitivity reactions.