Reduction of urate/uric acid formation in conditions where urate/uric acid deposition has already occurred or is a predictable clinical risk. Management of 2,8-dihydroxyadenine renal stones related to deficient activity of adenine phosphoribosyltransferase. Management of recurrent mixed Ca oxalate renal stones in the presence of hyperuricosuria, when fluid, dietary & similar measures have failed.
Adult 2-10 mg/kg/day if dose on mg/kg basis is required. Mild condition 100-200 mg daily. Moderately severe condition 300-600 mg daily. Severe condition 700-900 mg daily. Childn <15 yr 10-20 mg/kg/day. Max: 400 mg daily. Patient w/ severe renal insufficiency <100 mg/day, or single dose of 100 mg at longer intervals than 1 day. Patient undergoing dialysis 2-3 times/wk 300-400 mg immediately after each dialysis w/ none in the interim.
Adjust dose by monitoring serum urate conc & urinary urate/uric acid levels at appropriate intervals. Discontinue treatment at the 1st appearance of skin rash or other signs of allergic reaction. Do not rechallenge in patients w/ hypersensitivity syndrome & SJS/TEN. Consider screening for HLA-B*5801 before starting treatment. Do not start treatment in patients who are known HLA-B*5801 carriers unless there are no other reasonable therapeutic options & benefits exceed risks. Increased risk of developing allopurinol-associated hypersensitivity reactions in patients w/ chronic renal impairment & concomitant diuretic use (particularly thiazides). Not indicated for use in asymptomatic hyperuricaemia. Do not start treatment until acute attack of gout has completely subsided, as further attacks may be precipitated. Adequately hydrate to minimise risk of xanthine deposition in conditions where rate of urate formation is greatly increased. Possibility of impaction of uric acid renal stones in the ureter. Increased TSH values in patients on long-term treatment. Do not administer to patients w/ rare hereditary problems of galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption. Use reduced doses in patients w/ hepatic or renal impairment. Use in pregnancy only when there is no safer alternative & when the disease itself carries risks for the mother or unborn child. Not recommended during breastfeeding.
Prolonged activity of 6-mercaptopurine & azathioprine. Increased plasma t½ of vidarabine. Decreased therapeutic activity w/ salicylates & uricosuric agents (eg, probenecid). Increased risk of prolonged hypoglycaemic activity if given concomitantly w/ chlorpropamide when renal function is poor. Increased effect of warfarin & other coumarin anticoagulants. Inhibited metabolism of theophylline. Increased frequency of skin rash if concurrently given w/ ampicillin or amoxicillin. Frequent occurrence of blood dyscrasias w/ co-administration of cytostatics (eg, cyclophosphamide, doxorubicin, bleomycin, procarbazine, alkyl halogenides). Increased plasma conc of ciclosporin. Doubled plasma Cmax & AUC values of didanosine. Increased serum urate & plasma oxypurinol conc w/ co-administration of furosemide. Increased risk of hypersensitivity when co-administered w/ diuretics (particularly thiazides) or ACE inhibitors, especially in renal impairment. Attenuated effect w/ Al hydroxide.
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