A patient receives probenecid for gout while taking furosemide. The expected pharmacokinetic interaction is:

• A Probenecid accelerates hepatic metabolism of furosemide, reducing its diuretic effect
• B Probenecid competes for organic anion transporters in the proximal tubule, delaying furosemide delivery to its luminal site of action and blunting natriuresis ✓
• C Probenecid displaces furosemide from albumin, increasing free drug and causing excessive diuresis
• D Probenecid induces P-glycoprotein in the gut, decreasing furosemide bioavailability

Explanation

Loop diuretics must reach the tubular lumen to access the NKCC2 transporter on the luminal membrane. They gain entry primarily via organic anion transporters in the proximal tubule. Probenecid is itself an organic anion and competitively inhibits this transport, reducing luminal furosemide concentrations and weakening the diuretic response. Protein binding displacement is not clinically significant here, and furosemide is not dependent on hepatic metabolism or P-glycoprotein for its effect.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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