Furosemide, sold under the brand name Lasix among others, is a loop diuretic medication used to treat edema due to heart failure, liver scarring, or kidney disease.

[4] Common side effects include orthostatic hypotension (decrease in blood pressure while standing, and associated lightheadedness), tinnitus (ringing in the ears), and photosensitivity (sensitivity to light).

[14] It is often viewed as a first-line agent in most people with edema caused by congestive heart failure because of its anti-vasoconstrictor and diuretic effects.

[19][20] Providing self-administered subcutaneous furosemide has been found to reduce hospital admissions in people with heart failure, resulting in significant savings in healthcare costs.

[21][22] Furosemide is also used for liver cirrhosis, kidney impairment, nephrotic syndrome, in adjunct therapy for swelling of the brain or lungs where rapid diuresis is required (IV injection), and in the management of severe hypercalcemia in combination with adequate rehydration.

Reported cases of furosemide-induced hearing loss appeared to be associated with rapid intravenous administration, high dosages, concomitant renal disease, and coadministration with other ototoxic medication.

[35] This suggests the long-term consequences of loop diuretics on hearing could be a more significant than previously thought and further research is required in this area.

Other precautions include nephrotoxicity, sulfonamide (sulfa) allergy, and increased free thyroid hormone effects with large doses.

[38] 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 the development of acidosis, as it is with the carbonic anhydrase inhibitors.

Brand names under which furosemide is marketed include Aisemide, Apo-Furosemide, Beronald, Desdemin, Discoid, Diural, Diurapid, Dryptal, Durafurid, Edemid, Errolon, Eutensin, Farsiretic, Flusapex, Frudix, Frusemide, Frusetic, Frusid, Fulsix, Fuluvamide, Furantril, 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, Seguril, Teva-Furosemide, Trofurit, Uremide, and Urex.

Sometime in the early 1970s, furosemide's ability to prevent, or at least greatly reduce, the incidence of bleeding by horses during races was discovered accidentally.

[citation needed] Furosemide is also used in horses for pulmonary edema, congestive heart failure (in combination with other drugs), and allergic reactions.

Overdose may lead to dehydration, change in drinking patterns and urination, seizures, gastrointestinal problems, kidney damage, lethargy, collapse, and coma.

It may also cause interactions with anesthetics, so its use should be related to the veterinarian if the animal is going into surgery, it decreases the kidneys' ability to excrete aspirin, so dosages will need to be adjusted if combined with that drug.