What is Lasix in horse racing?

Lasix, also known as Salix and furosemide, is a diuretic used to reduce extra fluid in the body.

In the racehorse, it is primarily used to diminish the likelihood of bleeding through the nostrils during periods of heavy exertion, such as a race, which can produce a suffocating feeling and prevent a horse from doing its best.

But critics have long argued that Lasix enhances performance by causing horses to rapidly lose weight and can also mask the use of prohibited substances.

As a result, its use on race days has long been prohibited in many racing jurisdictions, including in Europe and the U.K., but U.S. racing authorities are only now beginning to phase out its use as a race day medication. Read more about strategies in horse racing.