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Pharmacology · single question

Mechanism of action of triamterene?

  1. Inhibits Na-K-2Cl cotransporter in loop of Henle
  2. Blocks sodium channels in distal collecting duct, reducing potassium excretion
  3. Blocks aldosterone receptors in collecting duct
  4. Inhibits carbonic anhydrase in proximal tubule
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Correct answer: B. Blocks sodium channels in distal collecting duct, reducing potassium excretion

Triamterene = POTASSIUM-SPARING DIURETIC — blocks epithelial sodium channels (ENaC) in distal collecting duct. Reduces sodium reabsorption → decreases electrical gradient for potassium secretion → retains potassium. Combined with HCTZ to prevent HCTZ-induced hypokalemia.

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