"Lasix" redirects here. For the article on the method of eye surgery, see LASIK.
Systematic (IUPAC) name
4-chloro-2-(furan-2-ylmethylamino)- 5-sulfamoylbenzoic acid
Clinical data
AHFS/ monograph
Licence data US Daily Med:link
  • AU: C
  • US: C (Risk not ruled out)
  • (Prescription only)
Oral, IV, IM
Pharmacokinetic data
Bioavailability 43-69%
Metabolism hepatic and renal glucuronidation
Half-life up to 100 minutes
Excretion renal 66%, biliary 33%
54-31-9 7pxY
PubChem CID 3440
DrugBank DB00695 7pxY
ChemSpider 3322 7pxY
KEGG D00331 7pxY
ChEBI CHEBI:47426 7pxY
Chemical data
Formula C12H11ClN2O5S
330.745 g/mol
 14pxY (what is this?)  (verify)

Furosemide (INN/BAN[1]), previously frusemide (former BAN), is a loop diuretic used in the treatment of congestive heart failure and edema. It is most commonly marketed by Sanofi under the brand name Lasix, and also under the brand names Fusid and Frumex.[2] It has also been used to prevent Thoroughbred and Standardbred race horses from bleeding through the nose during races.

Along with some other diuretics, furosemide is also included on the World Anti-Doping Agency's banned drug list due to its alleged use as a masking agent for other drugs.

It is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system.[3]

Medical uses

Furosemide is primarily used for the treatment of hypertension and edema.[4] It is the first-line agent in most people with edema caused by congestive heart failure.[4] It is also used for hepatic cirrhosis, renal impairment, nephrotic syndrome, in adjunct therapy for cerebral or pulmonary edema where rapid diuresis is required (IV injection), and in the management of severe hypercalcemia in combination with adequate rehydration.[5]

Adverse effects

Although disputed,[6] it is considered ototoxic: "usually with large parenteral doses and rapid administration and in renal impairment".[7] Furosemide also can lead to gout caused by hyperuricemia. Hyperglycemia is also a common side effect.

The tendency, as for all loop diuretics, to cause low potassium levels (hypokalemia) has given rise to combination products, either with potassium itself (e.g. Lasix-K) or with the potassium-sparing diuretic amiloride (Co-amilofruse).


Furosemide has potential interactions with these medications:[8]

Mechanism of action

Main article: Loop diuretic

Furosemide, like other loop diuretics, acts by inhibiting NKCC2, the luminal Na-K-2Cl symporter in the thick ascending limb of the loop of Henle. The action on the distal tubules is independent of any inhibitory effect on carbonic anhydrase or aldosterone; it also abolishes the corticomedullary osmotic gradient and blocks negative, as well as positive, free water clearance.

Because of the large NaCl absorptive capacity of the loop of Henle, diuresis is not limited by development of acidosis, as it is with the carbonic anhydrase inhibitors.

By inhibiting the transporter, the loop diuretics reduce the reabsorption of NaCl and also diminish the lumen-positive potential that derives from K+ recycling. This electrical potential normally drives divalent cation reabsorption in the loop, and by reducing this potential, loop diuretics cause a decrease in Mg2+ and Ca2+ reabsorption. Prolonged use can cause significant hypomagnesemia in some patients. Since Ca2+ is actively reabsorbed in the distal convoluted tubule, loop diuretics generally do not cause hypocalcemia.

Additionally, furosemide is a noncompetitive subtype-specific blocker of GABA-A receptors.[9][10][11] Furosemide has been reported to reversibly antagonize GABA-evoked currents of α6β2γ2 receptors at µM concentrations, but not α1β2γ2 receptors.[9][11] During development, the α6β2γ2 receptor increases in expression in cerebellar granule neurons, corresponding to increased sensitivity to furosemide.[10]

Veterinary uses

The diuretic effects are put to use most commonly in horses to prevent bleeding during a race. Sometime in the early 1970s, furosemide's ability to prevent, or at least greatly reduce, the incidence of bleeding (exercise-induced pulmonary hemorrhage) by horses during races was discovered accidentally. In the United States of America, pursuant to the racing rules of most states, horses that bleed from the nostrils three times are permanently barred from racing (for their own protection), these rules do not apply in all countries. Clinical trials followed, and by decade's end, racing commissions in some states in the USA began legalizing its use on race horses. On September 1, 1995, New York became the last state in the United States to approve such use, after years of refusing to consider doing so. Some states allow its use for all racehorses; some allow it only for confirmed "bleeders". However, its use for this purpose is still prohibited in many other countries, and veterinarians dispute its use for this problem.

Furosemide is also used in horses for pulmonary edema, congestive heart failure (in combination with other drugs), and allergic reactions. Although it increases circulation to the kidneys, it does not help kidney function, and is not recommended for kidney disease.

It is also used to treat congestive heart failure in cats and dogs (which experience fluid on the lungs) and complications from heartworm. It can be used in conjunction with an antibiotic and anti-inflammatory to treat this condition. It can also be used in an attempt to promote diuresis in anuric or oliguric acute renal failure.

Precautions, side effects, and administration for horses

Furosemide is injected either intramuscularly or intravenously, usually 0.5-1.0 mg/kg twice/day, although less before a horse is raced. As with many diuretics, it can cause dehydration and electrolyte imbalance, including loss of potassium, calcium, sodium, and magnesium. Excessive use of furosemide will most likely lead to a metabolic alkalosis due to hypochloremia and hypokalemia. The drug should, therefore, not be used in horses that are dehydrated or experiencing kidney failure. It should be used with caution in horses with liver problems or electrolyte abnormalities. Overdose may lead to dehydration, change in drinking patterns and urination, seizures, gastrointestinal problems, kidney damage, lethargy, collapse, and coma.

Furosemide should be used with caution when combined with corticosteroids (as this increases the risk of electrolyte imbalance), aminoglycoside antibiotics (increases risk of kidney or ear damage), and trimethoprim sulfa (causes decreased platelet count). It may also cause interactions with anesthesics, so its use should be related to the veterinarian if the animal is going into surgery, and it decreases the kidneys' ability to excrete aspirin, so dosages will need to be adjusted if combined with that drug.

Furosemide may increase the risk of digoxin toxicity due to hypokalemia.

The drug is best not used during pregnancy or in a lactating mare, as it has been shown to be passed through the placenta and milk in studies with other species. It should not be used in horses with pituitary pars intermedia dysfunction (Cushings).

Furosemide is detectable in urine 36–72 hours following injection. Its use is prohibited by most equestrian organizations.

Clinical use in kidney disease

In chronic kidney diseases with hypoalbuminemia, it is used along with albumin to increase diuresis. It is also used along with albumin in nephrotic syndrome to reduce edema. [12]

Dose in normal renal function

  • Oral : 20 mg – 1 g daily
  • IV: 20 mg – 1.5 g daily

Doses titrated to response.


  • Molecular weight (daltons) 330.7
  • % Protein binding 91–99
  • % Excreted unchanged in urine 80–90
  • Volume of distribution (L/kg) 0.07–0.2
  • Half-life – normal/ESRF (hrs) 0.5–2/9.7

Dose in renal impairment GFR (ml/min)

  • 20–50 Dose as in normal renal function
  • 10–20 Dose as in normal renal function; increased doses may be required
  • <10 Dose as in normal renal function; increased doses may be required

Dose in patients undergoing renal replacement therapies

  • cAPD Not dialysed, dose as in GFR < 10 ml/min
  • HD Dialysed, dose as in GFR < 10 ml/min
  • HDF/high flux Dialysed, dose as in GFR < 10 ml/min
  • CAV/VVHD Not dialysed, dose as in GFR = 10–20 ml/min

Important drug interactions

Potentially hazardous interactions with other drugs:

Other information

  • 500 mg orally ≡ 250 mg IV
  • Excreted by tubular secretion, therefore in severe renal impairment (GFR 5–10 ml/min) lower doses are required due to accumulation in the body. It also can cause further renal damage and should be administered with caution.
  • Furosemide acts within 1 hour of oral administration (after IV peak effect within 30 minutes); diuresis is complete within 6 hours.

Brand names

Some of the brand names under which furosemide is marketed include: Aisemide, Apo-Furosemide, Beronald, Desdemin, Discoid, Diural, Diurapid, Dryptal, Durafurid, Edemid, Errolon, Eutensin, Flusapex, Frudix, Frusetic, Frusid, Fulsix, Fuluvamide, Furesis, Furix, Furo-Puren, Furon, Furosedon, Fusid.frusone, Hydro-rapid, Impugan, Katlex, Lasilix, Lasix, Lodix, Lowpston, Macasirool, Mirfat, Nicorol, Odemase, Oedemex, Profemin, Rosemide, Rusyde, Salix, Teva-Furosemide, Trofurit, Uremide, and Urex.


  2. "Frumex". 
  3. "WHO Model List of EssentialMedicines" (PDF). World Health Organization. October 2013. Retrieved 22 April 2014. 
  4. 4.0 4.1 "Furosemide". The American Society of Health-System Pharmacists. Retrieved 3 April 2011. 
  5. Rossi S, ed. (2004). Australian Medicines Handbook 2004 (5th ed.). Adelaide, S.A.: Australian Medicines Handbook Pty Ltd. ISBN 0-9578521-4-2. 
  6. Rais-Bahrami K, Majd M, Veszelovszky E, Short B (2004). "Use of furosemide and hearing loss in neonatal intensive care survivors". Am J Perinatol 21 (6): 329–32. PMID 15311369. doi:10.1055/s-2004-831887. 
  7. BNF 45 March 2003
  8. Brand name:Lasix - Generic name: Furosemide Prescription Drug Information, Side Effects - PDRHealth
  9. 9.0 9.1 Korpi ER, Kuner T, Seeburg PH, Lüddens H (1995). "Selective antagonist for the cerebellar granule cell-specific gamma-aminobutyric acid type A receptor". Mol. Pharmacology. 47 (2): 283–9. PMID 7870036. 
  10. 10.0 10.1 Tia S, Wang JF, Kotchabhakdi N, Vicini S (1996). "Developmental changes of inhibitory synaptic currents in cerebellar granule neurons: role of GABA(A) receptor alpha 6 subunit". J. Neurosci. 16 (11): 3630–40. PMID 8642407. 
  11. 11.0 11.1 Wafford KA, Thompson SA, Thomas D, Sikela J, Wilcox AS, Whiting PJ (1996). "Functional characterization of human gamma-aminobutyric acidA receptors containing the alpha 4 subunit". Mol. Pharmacol. 50 (3): 670–8. PMID 8794909. 
  12. BMC Nephrol. 2012 Aug 29;13:92. doi: 10.1186/1471-2369-13-92.The added-up albumin enhances the diuretic effect of furosemide in patients with hypoalbuminemic chronic kidney disease: a randomized controlled study. Phakdeekitcharoen B1, Boonyawat K Ann Pharmacother. 2003 May;37(5):695-700. Combined furosemide and human albumin treatment for diuretic-resistant edema. Elwell RJ1, Spencer AP, Eisele G

Further reading

  • Aventis Pharma (1998). Lasix Approved Product Information. Lane Cove: Aventis Pharma Pty Ltd.
  • Barbara Forney (2007). Understanding Equine Medications, Revised Edition (Horse Health Care Library). Eclipse Press. ISBN 1-58150-151-X. 

External links