Allopurinol-induced hepatotoxicity may ... be a hypersensitivity reaction to the drug. A generalized hypersensitivity vasculitis has rarely led to irreversible hepatotoxicity and death. The frequency of allopurinol-induced hypersensitivity reactions may be increased in patients with decreased renal function who receive allopurinol and a thiazide diuretic concomitantly. Allopurinol should usually not be administered to patients who have previously shown hypersensitivity to it or who have had a serious reaction to the drug.