Which drug is used to treat hyperuricemia by inhibiting xanthine oxidase?

• A. Allopurinol
• B. Probenecid
• C. Febuxostat
• D. Rasburicase

Answer: (A)

Blocking xanthine oxidase, the enzyme that converts purines into uric acid, lowers uric acid production. Allopurinol fits this role because it’s a purine analog that, after metabolism to oxypurinol, potently inhibits xanthine oxidase. This reduces the formation of uric acid, helping to lower serum urate levels and prevent gout flares and urate crystal deposition. It’s a standard, long-established therapy for chronic gout and for preventing tumor lysis–related hyperuricemia. Other options work differently: some increase uric acid excretion, one degrades existing uric acid, and another XO inhibitor exists as an alternative, but allopurinol is the classic drug used to reduce uric acid production by inhibiting xanthine oxidase.