allopurinol: clinical use

Prescribing considerations

• Confirm a clinical indication rather than treating asymptomatic hyperuricaemia alone.
• Assess renal and hepatic function and interacting medicines before initiation.
• Counsel about rash, mucosal lesions, fever and systemic hypersensitivity symptoms; suspected serious hypersensitivity requires immediate permanent withdrawal.
• Consider HLA-B*58:01 testing in populations with high allele prevalence. A negative result does not eliminate SJS/TEN risk.
• Renal impairment, especially with diuretics, increases exposure and hypersensitivity risk.
• Acute gout flares may occur during early urate lowering; allopurinol does not treat acute pain.
• In high-cell-turnover states, coordinate with oncology or haematology and ensure appropriate hydration and biochemical monitoring.

Contraindications and cautions

• Hypersensitivity to allopurinol or any product excipient.
• Do not rechallenge after allopurinol hypersensitivity syndrome, DRESS, Stevens–Johnson syndrome or toxic epidermal necrolysis.
• Selected tablets contain lactose and are unsuitable for specified rare hereditary disorders of galactose metabolism or absorption.

Monitoring

• Serum urate.
• Renal function, including reassessment when clinical status or interacting medicines change.
• Liver function, particularly early in treatment or if symptoms develop.
• Full blood count when clinically indicated, especially with cytotoxic or thiopurine therapy or symptoms of marrow suppression.
• Consider thyroid assessment with pre-existing thyroid dysfunction or relevant clinical concern.

Clinical pharmacology

Allopurinol inhibits xanthine oxidase and is converted to the longer-acting active metabolite oxipurinol. Both reduce plasma and urinary uric acid. Oxipurinol is mainly cleared by the kidneys, making renal function an important determinant of exposure.

Formulation and product differences

• Both selected products are uncoated oral tablets containing lactose.
• The Aurobindo/Milpharm product is round and marked “MAL 100”.
• The Ipca product is marked “AL” and “100”; its break line assists swallowing but does not provide equal portions.
• Excipients, markings and pack presentation can differ between manufacturers; check the specific pack leaflet when switching.

Tablet

Route: Oral

Strengths: 100 mg, 200 mg, 300 mg