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Furosemide: Side effects

Furosemide is a loop diuretic. Furosemide’s mechanism of action is through inhibition of the Na-K-Cl cotransporter in the ascending loop of Henle by binding to this chloride transport channel and inhibiting the reabsorption of sodium, chloride, and potassium. It is used to treat hypertension and edema, and is the first line agent in most people with edema caused by heart failure.

Side effects:

• Hypotension

• Hypokalemia

• Ototoxicity (usually when given in large doses IV, or when given with aminoglycosides)

• Long term use may cause thiamine deficiency.

• Furosemide may increase risk of digoxin toxicity due to hypokalemia

• Hyperuricemia leading to gout.

• Hyperglycemia

Updated definition 2020:

Furosemide is one of the most commonly prescribed loop diuretics. It is frequently used to treat conditions associated with volume overload and edema potentially secondary to heart, liver, or renal failure. Its mechanism of action is related to the inhibition of the Na-K-2CL cotransporter located along the thick ascending limb of the loop of Henle. Loop diuretics have a characteristic threshold plasma concentration that must be reached before its diuretic effects are observed. Above this dose, loop diuretics exhibit a steep dose response curve. Route of administration can also affect a patient’s response to furosemide. Intravenous administration typically results in a brisker response than oral administration. Heart failure exacerbations with associated gut edema can further worsen the efficacy of orally administered furosemide, sometimes necessitating the use of IV diuretics during this time.

Common side effects of loop diuretics are hypersensitivity reactions, extracellular fluid volume depletion resulting in orthostatic hypotension and dehydration, ototoxicity, and electrolyte abnormalities. Hypokalemia, hypomagnesemia, hypocalcemia, hyperglycemia, and hyperuricemia can all occur with furosemide administration. Metabolic alkalosis can also be seen with administration.


  1. Katta, N; Balla, S; Alpert, MA (July 2016). "Does Long-Term Furosemide Therapy Cause Thiamine Deficiency in Patients with Heart Failure? A Focused Review". The American Journal of Medicine. 129 (7): 753.e7–753.e11. doi:10.1016/j.amjmed.2016.01.037. PubMed Link
  2. Ellison DH. Clinical Pharmacology in Diuretic Use. Clinical Journal of the American Society of Nephrology. 2019;1248-1257 PubMed Link

Other References

  1. Khan TM, Patel R, Siddiqui AH. Furosemide. In: StatPearls Publishing. 2020. Accessed 4 April 2020. Link