From the Guidelines
Allopurinol should be given to patients with gout when their serum uric acid (SUA) level is >8 mg/dL, or in patients with comorbidities, and started at a low dose (100 mg/day) with subsequent dose titration to target. When deciding to initiate allopurinol, it is essential to consider the patient's kidney function, as the maximum dosage should be adjusted according to creatinine clearance 1. The treatment goal is to maintain the SUA level <6 mg/dL (360mmol/L) lifelong, with a lower target (<5 mg/dL; 300mmol/L) for patients with severe gout until total crystal dissolution and resolution of gout 1. Key points to consider when initiating allopurinol include:
- Starting at a low dose (100 mg/day) and increasing by 100 mg increments every 2–4 weeks if required 1
- Adjusting the maximum dosage according to creatinine clearance in patients with renal impairment 1
- Maintaining the SUA level <6 mg/dL (360mmol/L) lifelong, with regular monitoring and dose titration as needed 1
- Considering a lower SUA target (<5 mg/dL; 300mmol/L) for patients with severe gout until total crystal dissolution and resolution of gout 1 According to the 2020 American College of Rheumatology guideline, allopurinol is strongly recommended as the preferred first-line agent for all patients, including those with CKD stage ≥3, and should be started at a low dose with subsequent dose titration to target 1.
From the FDA Drug Label
The correct size and frequency of dosage for maintaining the serum uric acid just within the normal range is best determined by using the serum uric acid level as an index. The dose of allopurinol tablets recommended for management of recurrent calcium oxalate stones in hyperuricosuric patients is 200 to 300 mg/day in divided doses or as the single equivalent Children, 6 to 10 years of age, with secondary hyperuricemia associated with malignancies may be given 300 mg allopurinol tablets daily while those under 6 years are generally given 150 mg daily. With a creatinine clearance of 10 to 20 mL/min, a daily dosage of 200 mg of allopurinol tablets is suitable. When the creatinine clearance is less than 10 mL/min, the daily dosage should not exceed 100 mg.
Key Considerations:
- The dosage of allopurinol should be adjusted based on the serum uric acid level.
- The recommended dose for adults with gout or hyperuricemia is not explicitly stated, but the dose for recurrent calcium oxalate stones is 200-300 mg/day.
- For children with secondary hyperuricemia, the dose is 300 mg/day for those 6-10 years old and 150 mg/day for those under 6 years old.
- Renal function should be considered when determining the dose, with reduced doses recommended for those with creatinine clearance < 20 mL/min 2.
- Allopurinol tablets are generally better tolerated if taken following meals 2.
From the Research
Indications for Allopurinol
Allopurinol is used to prevent flare-ups in patients with gout, particularly those with certain risk factors and conditions, including:
- Chronic kidney disease
- Two or more flare-ups per year
- Urolithiasis
- The presence of tophus
- Chronic gouty arthritis
- Joint damage 3
Patient Selection
The decision to start allopurinol should be based on individual patient factors, such as:
- Baseline serum uric acid (SUA) level
- Presence of comorbidities, such as chronic kidney disease
- History of gout flare-ups
- Tolerance to anti-inflammatory medications 4, 5
Dosing and Monitoring
Allopurinol dosing should be titrated to achieve a target serum urate level, with monitoring of:
- Serum uric acid levels
- Oxypurinol levels to guide therapy 6
- Patient response to treatment, including reduction in gout flare-ups and improvement in symptoms
Special Considerations
Allopurinol may be particularly beneficial in patients with gout who are at risk of developing uric acid stones, as it can change the stone composition distribution to a pattern similar to that in stone formers without gout 7
- Patients with gout who are on allopurinol may have fewer pure uric acid stones and more calcium oxalate monohydrate stones than those without medication 7