Pharmacology · Class
Loop diuretics !
The strongest diuretics: they block salt reabsorption in the thick ascending limb of the loop of Henle and remove fluid fast.
Updated 2026-11-01
What they are
Diuretics that inhibit the Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) in the thick ascending limb of the loop of Henle. They are used for oedema from heart failure, cirrhosis and kidney disease, and for acute pulmonary oedema.
Mechanism of action
From the tubular lumen they block NKCC2, so sodium, potassium and chloride stay in the urine. The kidney loses its ability to concentrate urine, water follows the salt, and more potassium, magnesium and calcium are lost in the urine.
Target: Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2)
Drugs in this class
- FurosemideThe most used loop diuretic: it removes fluid quickly in heart failure, pulmonary oedema and other oedemas, and lowers…Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) of the loop of Henle
- BumetanideA loop diuretic far more potent per milligram than furosemide, with fast onset and short action. Used for oedema.Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) of the loop of Henle
- Etacrynic acidA loop diuretic that is not a sulfonamide, kept for patients with sulfonamide allergy. It is the most ototoxic of its…Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) of the loop of Henle
- TorasemideA loop diuretic with reliable oral absorption and longer action than furosemide. Used for oedema and high blood…Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) of the loop of Henle
Others in the class
- Piretanide
Test yourself
Think of the answer, then tap the question to see it.
Which transporter do loop diuretics block, and where?
The Na⁺-K⁺-2Cl⁻ cotransporter (NKCC2) on the luminal side of the thick ascending limb of the loop of Henle.
Why do loop diuretics increase calcium loss in urine, unlike thiazides?
NKCC2 creates the positive lumen voltage that drives calcium and magnesium between cells; blocking it removes that drive, so more calcium and magnesium leave in the urine.
Which loop diuretic is not a sulfonamide?
Etacrynic acid, an option when there is a true sulfonamide allergy, although it is more ototoxic.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - FUROSEMIDE injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Furosemide: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.