Pharmacology of Loop Diuretics

Mechanism of Action:

Loop diuretics primarily act on the ascending limb of the Loop of Henle in the kidneys. They inhibit the sodium-potassium-chloride (Na-K-Cl) co-transporter, which leads to a decrease in the reabsorption of these ions. This action results in an increase in the osmolarity of the filtrate, causing more water to be drawn into the nephron and ultimately leading to increased urine output.

Loop Diuretics MOA
#Diuretics MOA
Loop diuretics
#Image Source: – Antonietta, Cicoira & Calvi, Emiliano & Faggiano, Andrea & Maffeis, Caterina & Bosisio, Marco & Stefano, Marco & Carugo, Stefano & Faggiano, Pompilio. (2022). Impact of Loop Diuretic on Outcomes in Patients with Heart Failure and Reduced Ejection Fraction. Current Heart Failure Reports. 19. 1-11. 10.1007/s11897-021-00538-7.


  • Absorption: Generally well-absorbed from the gastrointestinal tract.
  • Distribution: Widely distributed in the body; some are protein-bound.
  • Metabolism: Liver metabolism for some agents like torsemide.
  • Excretion: Primarily renal excretion.

Drug Examples:

  • Furosemide (Lasix): Most commonly used; rapid onset of action.
  • Bumetanide (Bumex): More potent than furosemide but with a similar profile.
  • Torsemide (Demadex): Longer duration of action; also used for chronic conditions.

Clinical Use:

  1. Acute Heart Failure: Rapid diuresis to relieve pulmonary edema.
  2. Chronic Heart Failure: Used in combination with other drugs for long-term management.
  3. Edema: Due to liver or kidney disease.
  4. Hyperkalemia: To rapidly remove potassium from the body.
  5. Hypertension: Less commonly used for this purpose but effective.

Side Effects:

  • Hypokalemia: Low potassium levels
  • Hyponatremia: Low sodium levels
  • Hypomagnesemia: Low magnesium levels
  • Ototoxicity: Especially at high doses
  • Renal impairment: Risk of acute kidney injury

Drug Interactions:

  • ACE Inhibitors: Increased risk of renal impairment.
  • Digoxin: Increased risk of digoxin toxicity due to hypokalemia.
  • Lithium: Increased risk of lithium toxicity.


  • Severe renal impairment where diuresis is not expected.
  • Hypokalemia or other electrolyte imbalances.
  • Known hypersensitivity to sulfa drugs (for some loop diuretics).

Understanding the pharmacology of loop diuretics is crucial for healthcare providers to effectively treat conditions like heart failure and edema while minimizing side effects.

Disclaimer: This article is for informational purposes only and should not be taken as medical advice. Always consult with a healthcare professional before making any decisions related to medication or treatment.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always seek the advice of a healthcare provider with any questions regarding a medical condition.

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