Desensitization to allopurinol

Abstract Rationale Allopurinol is the most frequently prescribed drug for hyperuricemia. There are already several reports of severe adverse reactions to allopurinol, varying from maculo-papular rash (2%) to allopurinol hypersensitivity syndrome (0,004%). Desensitization is recommended in patients with confirmed allopurinol allergy and in whom uricosuric drugs are ineffective or contraindicated (e.g. renal calculi). Methods We performed allopurinol desensitization in 7 patients (6 males, 1 female; mean age: 57,2 (41-70) years) with hyperuricemia and renal calculi/tophaceous gout with documented allopurinol hypersensitivity manifested by cutaneous rash (6 patients) or facial pruritus (1 patient), which appeared after a period of allopurinol therapy ranging from 2 days to 5 months. We used the protocol suggested by Vervloet et al, with oral administration of increasing doses of allopurinol, during a period of 16 consecutive days, under close medical supervision, starting with a dose of 10 μg and trying to reach a daily dose of 300 mg. Results Five patients tolerated a daily dose of 300 mg, without any further adverse reactions. In one other patient the maintenance dose had to be reduced to 150 mg daily because of generalized pruritus with the 300 mg dose. One patient could not finish the induction phase due to adverse reaction (generalized erythema with 50 mg of allopurinol). Conclusions Our experience with this desensitization protocol in these patients corroborates its safeness and effectiveness in the management of allopurinol hypersensitivity, particularly in patients where there are no alternative therapeutic options.