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 is 200 to 300 mg per day for patients with mild gout and 400 to 600 mg per day for those with moderately severe tophaceous gout. The appropriate dosage may be administered in divided doses or as a single equivalent dose with the 300 mg tablet. Dosage requirements in excess of 300 mg should be administered in divided doses. The minimal effective dosage is 100 to 200 mg daily and the maximal recommended dosage is 800 mg daily.

Primary rat osteoblast cells were obtained from 2-day-old neonatal Sprague-Dawley rats. Following isolation, cells were resuspended in Dulbecco's Modified Essential Medium, supplemented with 10% foetal calf serum (FCS), 2 mM L-glutamine, 100 U/ml penicillin, 100 mg/ml streptomycin and 0.25 mg/ml amphotericin (complete mixture abbreviated to DMEM). Cells were cultured for 2–4 days in a humidified atmosphere of 5% CO2–95% air at 37 °C in 75 cm2 flasks until confluent. Upon confluence, cells were sub-cultured into 24- well trays in DMEM supplemented with 2 mM β-glycerophosphate, 50 μg/ml ascorbic acid and 10 nM dexamethasone (supplemented DMEM), with half medium changes every 3 days. Osteoblasts were cultured in the presence of allopurinol and oxypurinol (1 nM–10 mM) to determine the effect on cell proliferation, differentiation, function and gene expression. For the bone formation experiments, cells were also treated with febuxostat and, as a positive control of an anabolic agent, BMP2 (0.1 mM). Unless stated, experiments were carried out at 2 time points during the osteoblast culture; day 7, which represents differentiating osteoblasts, and day 14 (mature, bone forming osteoblasts). All experiments were carefully pH-controlled because bone mineralisation is extremely sensitive to inhibition by acidosis