Allopurinol

Suggested dosage schedules from the SPC: 100 to 200 mg daily in mild conditions; 300 to 600 mg daily in moderately severe conditions; 700 to 900 mg daily in severe conditions. If dosage on a mg/kg bodyweight basis is required, 2 to 10 mg/kg bodyweight/day should be used. OLDER PEOPLE: in the absence of specific data, the lowest dosage which produces satisfactory urate reduction should be used, with particular attention to the renal impairment advice and to section 4.4. Extra caution should be exercised if renal function is poor. Hepatic impairment: reduced doses should be used, with periodic liver function tests during the early stages of therapy. High urate turnover conditions (e.g. neoplasia, Lesch-Nyhan syndrome): correct existing hyperuricaemia and/or hyperuricosuria before starting cytotoxic therapy, ensure adequate hydration and attempt urinary alkalinisation, and dose at the lower end of the recommended schedule. Adjust dosage by monitoring serum urate concentrations and urinary urate/uric acid levels at appropriate intervals. Screening for HLA-B*5801 should be considered before starting in patient subgroups where prevalence of the allele is high (Han Chinese, Thai, Korean descent), as it is associated with hypersensitivity syndrome and SJS/TEN. Withdraw immediately if a hypersensitivity reaction occurs; do not rechallenge after hypersensitivity syndrome or SJS/TEN. The SPC states no explicit adult maximum dose, so maxDose has been left out deliberately.

Children under 15 years: the SPC states 10 to 20 mg/kg bodyweight/day up to a maximum of 400 mg daily - a range, not a single per-kg figure, so dosePerKg is left null rather than inventing a value. Use in children is rarely indicated, except in malignant conditions (especially leukaemia) and certain enzyme disorders such as Lesch-Nyhan syndrome. Verify against a children's formulary before prescribing.