Adults: The dosage of allopurinol to accomplish full control of gout and to lower serum uric acid to normal or near-normal levels varies with the severity of the disease.
The average dose is for patients with mild gout, 200-300 mg/day and for those with moderately severe tophaceous gout, 400-600 mg/day. The appropriate dosage may be administered in divided doses or as a single equivalent dose with the 300 mg tablet. Dosage requirement in excess of 300 mg should be administered in divided doses.
The minimal effective dose is 100-200 mg/day and the maximal recommended dose is 800 mg/day. To reduce the possibility of flare-up of acute gouty attacks, it is recommended that the patient start with a low-dose of allopurinol (100 mg daily) and increase at weekly intervals by 100 mg until a serum uric acid level of ≤6 mg/dL is attained but without exceeding the maximal recommended dose. Normal serum urate levels are usually achieved in 1-3 weeks. The upper limit of normal (ULN) is about 7 mg/dL for men and postmenopausal women and 6 mg/dL for premenopausal women. Too much reliance should not be placed on a single serum uric acid determination since, for technical reasons, estimation of uric acid may be difficult. By selecting the appropriate dosage and, in certain patients, using uricosuric agents concurrently, it is possible to reduce serum uric acid to normal or, if desired, to as low as 2-3 mg/dL and keep it there indefinitely.
Since allopurinol and its metabolites are primarily eliminated only by the kidney, accumulation of the drug can occur in renal failure, and the dose of allopurinol should consequently be reduced. With a creatinine clearance (CrCl) of 10-20 mL/min, a daily dose of 100-200 mg of allopurinol is suitable. When the CrCl is <10 mL/min, the daily dose should not exceed 100 mg. With extreme renal impairment, (CrCl <3 mL/min) the interval between doses may also need to be lengthened. If facilities are available to monitor plasma oxipurinol concentrations, the dose should be adjusted to maintain plasma oxipurinol levels <100 mcmol/mL (15.2 mg/mL).