Milurit (Allopurinol)

Allopurinol is a xanthine oxidase inhibitor used in disorders of uric acid metabolism.

• Gout: reduces serum uric acid levels, decreasing the frequency of acute attacks.
• Hyperuricemia: lowers elevated uric acid concentrations to target ranges.
• Tumor lysis syndrome prophylaxis: prevents rapid rise in uric acid during cancer therapy.

• Allopurinol is metabolized to oxypurinol, which competitively inhibits the enzyme xanthine oxidase. By blocking this key step in purine degradation, the conversion of hypoxanthine to xanthine and xanthine to uric acid is reduced, leading to decreased production of uric acid and lower serum urate concentrations. The inhibition is sustained because oxypurinol has a longer half‑life than the parent drug, providing prolonged urate‑lowering effect throughout dosing intervals.

Allopurinol may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Rash: mild skin eruptions or itching.
• Gastrointestinal upset: nausea, vomiting or abdominal discomfort.
• Elevated liver enzymes: transient increase in hepatic transaminases.
• Diarrhea: loose stools, usually self‑limiting.
• Headache: mild to moderate head pain.

Serious or Rare Side Effects

• Severe cutaneous adverse reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• Aplastic anemia: bone‑marrow failure leading to pancytopenia.
• Hepatotoxicity: significant liver injury with jaundice.
• Acute interstitial nephritis: kidney inflammation causing renal impairment.
• Hypersensitivity syndrome: fever, eosinophilia and organ involvement.

When prescribing Allopurinol, several safety considerations should be observed.

• Renal function: adjust dose in patients with impaired kidney function.
• Hepatic impairment: monitor liver enzymes during therapy.
• Hypersensitivity risk: discontinue immediately if rash or systemic symptoms develop.
• Drug interactions: review concomitant medications that may increase toxicity.
• Pregnancy and lactation: use only if clearly needed, as safety data are limited.
• Store at ambient temperature: keep below 25°C in the original container, protect from moisture.

Allopurinol can interact with several medicines, affecting its efficacy or safety.

Major Interactions (Avoid)

• Azathioprine or mercaptopurine: increased risk of bone‑marrow suppression.
• Warfarin: enhanced anticoagulant effect, may require INR monitoring.
• Amoxicillin‑clavulanate: higher incidence of severe skin reactions.

Moderate Interactions (Monitor Closely)

• Thiazide diuretics: may reduce urate‑lowering effect.
• ACE inhibitors or ARBs: may increase serum potassium when combined with allopurinol.
• High‑dose vitamin C: may augment uric acid reduction, monitor for kidney stones.