Probenecid lowers serum urate in patients with gout by which mechanism?

• A Irreversible inhibition of xanthine oxidase in the liver
• B Conversion of urate to the more soluble allantoin
• C Inhibition of urate reabsorption via URAT1 and organic acid transporters in the proximal tubule ✓
• D Competitive inhibition of urate binding to albumin, increasing filtered load

Explanation

Probenecid is a uricosuric that blocks reabsorption of uric acid in the proximal convoluted tubule, mainly through inhibition of the URAT1 transporter and related organic anion transporters, thereby increasing urinary urate excretion. It is useful in underexcretors with normal renal function but loses efficacy once creatinine clearance falls substantially. It does not touch xanthine oxidase, humans lack uricase so allantoin conversion requires recombinant enzymes like rasburicase, and plasma protein binding is irrelevant here.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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