Following his third episode of gouty arthrits, a 50-year-old man sees you in the clinic. Each case was successfully treated acutely; however, your patient is interested in trying to prevent further episodes. He is not on regular medications and has a normal physical examination today. Blood work reveals an elevated serum uric acid level and otherwise normal renal function and electrolytes. A 24-hour urine collection for uric acid reveals that he is under-excreting uric acid. Suspecting that this is a case of recurrent gout, you place him on probenecid