Furosemide is a loop diuretic medication used to treat fluid build-up due to heart failure, liver scarring, or kidney disease. It may also be used for the treatment of high blood pressure. It can be taken by injection into a vein or by mouth. When taken by mouth, it typically begins working within an hour, while intravenously, it typically begins working within five minutes.Common side effects include feeling lightheaded with standing, ringing in the ears, and sensitivity to light. Potentially serious side effects include electrolyte abnormalities, low blood pressure, and hearing loss. Blood tests are recommended regularly for those on treatment. Furosemide is a type of loop diuretic that works by decreasing the reabsorption of sodium by the kidneys. Common side effects of furosemide injection include hypokalemia (low potassium level), hypotension (low blood pressure), and dizziness.Furosemide was patented in 1959 and approved for medical use in 1964. It is on the World Health Organizations List of Essential Medicines. In the United States, it is available as a generic medication. In 2020, it was the nineteenth most commonly prescribed medication in the United States, with more than 26 million prescriptions. In 2020/21 it was the twentieth most prescribed medication in England. It is on the World Anti-Doping Agencys banned drug list due to concerns that it may mask other drugs. It has also been used in race horses for the treatment and prevention of exercise-induced pulmonary hemorrhage.
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 restricted by most equestrian organizations. In April 2019, it was announced that Lasix would be banned from use at US racetracks within 24 hours of a horse racing starting in 2021. References
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 978-1-58150-151-3. External links

"Furosemide". Drug Information Portal. U.S. National Library of Medicine. "Furosemide Injection". MedlinePlus. Lasix and horse bleeding