• Allopurinol should not be started until an acute attack of gout has completely subsided, as the drug may precipitate further attacks.
• In most people, allopurinol 100 mg once a day can be started (preferably taken after food) [Jordan et al, 2007]. The dose can then be increased by 50–100 mg increments approximately every 2–3 weeks until a dose of 300 mg is reached, then check the person's serum uric acid (SUA) level and renal function at 3 months.
• Increase doses further to achieve a SUA level below 300 micromol/L. The maintenance dose is often in the region of allopurinol 300 mg a day, but maintenance doses may vary between 100–900 mg a day depending on the severity of the gout, and the dose required to maintain the SUA at an appropriate level.
• Allopurinol is usually given once a day. Doses over 300 mg per day should be taken in divided doses, which will help minimize any gastrointestinal adverse effects.
• It is important that allopurinol dose adjustment is based on:
• SUA levels (i.e. the aim is to achieve a SUA level below 300 micromol/L).
• Renal function (urea and electrolytes).
• Clinical response and how well the allopurinol is tolerated.
• The time it takes serum urate to reach target level will depend on the severity of the gout (takes longer in people with tophi), and the number of joints affected.
• In elderly people, those with frequent attacks, those with renal impairment (glomerular filtration rate less than 60 mL/min), and those with hepatic impairment, it may be safer to start with allopurinol 50 mg a day. See Managing renal impairment for more information. Note: allopurinol 50 mg tablets are not available, so when providing a 50 mg dose, check that the 100 mg tablets are scored for easier dose administration.

[ABPI Medicines Compendium, 2006; Jordan et al, 2007]