Question

Furosemide mechanism of action

• A. Inhibit Na⁺-K⁺-2Cl⁻ cotransporter in the ascending limb of Henle
• B. Inhibit Na⁺-K⁺ cotransporter in the collecting duct
• C. Inhibit Na⁺-2Cl⁻ cotransporter in the distal loop of Henle
• D. Aldosterone antagonist

Hint:

Furosemide is called a "high-ceiling" diuretic due to its powerful action. It may cause hypokalemia and ototoxicity with prolonged use.

Answer 1

The Correct Option is A

Furosemide is grouped as a loop diuretic because of exactly where in the nephron it works and which transporter it shuts down.

1. Na+-K+-2Cl- cotransporter, ascending limb: This is the actual site and target. Blocking this transporter in the thick ascending limb stops a large fraction of sodium and chloride reabsorption, driving a strong diuretic effect and interfering with the kidney's usual urine-concentrating mechanism.
2. Na+-K+ cotransporter, collecting duct: The collecting duct does not rely on this transporter for sodium handling, so this does not describe furosemide.
3. Na+-2Cl- cotransporter, distal loop: Wrong transporter composition and wrong nephron segment for furosemide's actual site of action.
4. Aldosterone antagonist: Describes a different diuretic class entirely, the potassium-sparing diuretics acting in the collecting duct, not furosemide.

The mechanism that matches furosemide is blocking the Na+-K+-2Cl- cotransporter in the ascending limb of the loop of Henle.

So the correct answer is Inhibit Na+-K+-2Cl- cotransporter in the ascending limb of Henle.