Which uricosuric agent increases renal excretion of uric acid by inhibiting proximal tubule reabsorption?

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

Answer: (C)

The key idea is that a uricosuric drug boosts uric acid elimination by blocking its reabsorption in the proximal tubule. Urate filtered by the kidney is largely reabsorbed via transporters in the proximal tubule, especially URAT1. Probenecid inhibits these reabsorption transporters, so more uric acid stays in the urine and is excreted, lowering blood levels. The other drugs don’t work this way: febuxostat and allopurinol reduce the production of uric acid by inhibiting xanthine oxidase, not its reabsorption or excretion; pegloticase enzymatically breaks down uric acid to allantoin, reducing levels through degradation rather than renal excretion. That’s why probenecid is the uricosuric agent described.