Furosemide “Might Be Justifiable”
By The Editors

According to the results of a study released today,

Furosemide [Lasix/Salix], used in the United States and Canada to treat bleeding into the airways in thoroughbred racehorses, decreases the incidence of hemorrhage according to results of a recent study….

The study involved 167 horses randomly allocated to race fields of nine to 16 horses each. Each horse raced in two races, one week apart, in the same field and in races of the same distance. In the blinded study, each horse received furosemide before one race and saline solution before the other race. Horses raced under typical racing conditions. Endoscopy was performed within 30-90 minutes after racing to identify the presence of blood in airways.

The research showed that giving furosemide before a race dramatically decreased the incidence and severity of exercise-induced pulmonary hemorrhage, or EIPH. Horses were three to four times more likely to have any evidence of bleeding without furosemide … seven to 11 times more likely to have severe bleeding without it.

The study, conducted by researchers at Colorado State University, the University of Melbourne and the University of Pretoria, concludes,

Results of the study provide strong evidence that furosemide can help prevent the development of EIPH in Thoroughbred racehorses. As such, its use in racehorses might be justifiable, assuming that other regulatory and policy issues important to the integrity of the sport are adequately addressed.

That last is a key phrase.

The study will be published in the Journal of the American Veterinary Medicine Association on July 1, 2009. Interested readers can download a PDF already available.


  • Thanks for stressing that last sentence.

    Like most medications, Lasix masks, but doesn’t solve, the actual problem. The conclusion of this study sounds remarkably similar to those studies in the early 70s which predicted that with the added “security” raceday medications offer, legalizing those would be a surefire way to increase the number of starts per racehorse/year.

    The results are in, and those 70s scientists were idiots (or, more likely, they were smart and unethical enough to know exactly who funded their research and what they wanted to hear). It takes some guts to trot out not only the same erroneous conclusion, but in fact base your study on a “finding” that has been proven for almost 40 years.

    Empirical evidence is to the contrary. The sounder horses are bred where the usage of drugs such as (and specifically) Lasix is forbidden.

    The German breeding industry currently goes through a phase of unprecedented success, thanks in part to a strategic decision a decade ago to allow only such sires that haven’t raced on medications themselves. Meanwhile the most infirm racehorses on the globe are bred in America, where the usage of Lasix and other medications “proven” to decrease the number of breakdowns has been commonplace for decades.

  • Thanks for the comment and for mentioning the German breeding industry, which has an excellent representative in Monsun. (More on the sire of Stacelita, Shirocco, and other stakes winners from Sid Fernando.)

    One thing I was struck by reading the paper is that 57% of horses that ran in both races showed signs of EIPH after the administration of furosemide, as did nearly 80% of the horses that received the placebo. Can it be assumed that EIPH is that prevalent across racehorse populations, even those that do not race on medications?

  • A very interesting overview about EIPH can be found on Horsequest.

    The problem is indeed common amongst non-medicated horses (and non-Thoroughbreds) too, but the effect of Furosemide (Lasix) is not limited to treating EIPH.

    Obviously I’m not an expert on the subject, but Veterinarians in racing jurisdictions that have earned a good standing when it comes to equine safety have held that the negative effects of administering Furosemide far outweigh the (long-proven) effect it has in regards to EIPH.