Less than 1% risk of adverse reactions of allopurinol

Dear Ask The Doctor: If I take allopurinol for my gout and stop it at any first sign of negative side effects, can I stop Stevens Johnson syndrome or can the progression still continue even if I stop it?

Dear Jason: Allopurinol has been associated with a number of hypersensitivity reactions, including vasculitis and Stevens-Johnson syndrome, with risk of <1% of developing these adverse reactions. It is advised to discontinue allopurinol at first sign of symptoms with the half-life elimination of the drug, in a patient with normal kidney function, of 1 3 hours, and an additional metabolite of the drug is 18 30 hours. Therefore a severe reaction may occur with therapy but you can minimise or prevent progression by immediate discontinuation.