Pharmacology · single question
What is the mechanism of action of allopurinol in treating gout?
Show answer and explanation
Correct answer: D. Inhibits xanthine oxidase, reducing uric acid production
Allopurinol inhibits xanthine oxidase, the enzyme responsible for converting hypoxanthine → xanthine → uric acid. By blocking this final step, allopurinol reduces uric acid production and prevents crystal deposition in joints and soft tissues. It is used for chronic gout prevention (not acute attacks). Probenecid works differently — it increases renal excretion of uric acid.
- A. ❌ COX-2 inhibitors (celecoxib, NSAIDs) reduce acute gout inflammation but do not lower uric acid levels.
- B. ❌ Probenecid and lesinurad block uric acid reabsorption (URAT1 inhibitors) — not allopurinol.
- C. ❌ No approved drug directly dissolves urate crystals; rasburicase converts uric acid to allantoin but doesn't dissolve crystals.
- D. ✅ CORRECT – Allopurinol inhibits xanthine oxidase, reducing the conversion of purines to uric acid.