A patient with hypertension and hypokalemia is started on a potassium-sparing diuretic that acts independently of aldosterone. Which specific channel does this drug block in the distal nephron?

• A Na-K-2Cl cotransporter in the thick ascending limb
• B Aquaporin-2 water channel in the collecting duct
• C Na-Cl cotransporter in the distal convoluted tubule
• D Epithelial sodium channel (ENaC) in the collecting duct ✓

Explanation

Amiloride and triamterene are potassium-sparing diuretics that directly block ENaC channels in the cortical collecting duct, independent of aldosterone levels. Spironolactone acts as an aldosterone receptor antagonist, not a direct channel blocker. The Na-K-2Cl cotransporter is the loop diuretic target, and aquaporin-2 is the V2 receptor-mediated channel.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.