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Lasix: Colorado State University Provides New Findings On Controversial Racehorse Drug


By Jeff Dodge

As the debate over the controversial drug Lasix heated up in advance of the Breeders’ Cup, held October 31-November 1 at Santa Anita Park in Arcadia, Calif., a Colorado State University researcher released new study results about the impact that bleeding in the lungs has on racehorses’ performance and the effectiveness of the most common treatment for the condition.

Lasix, the original brand name for a diuretic called furosemide, is used by horse owners to reduce exercise-induced pulmonary hemorrhaging (EIPH), the bleeding in the lungs that commonly occurs while horses are racing.

The use of the medication was banned by the Breeders’ Cup last year (2013) in races that were limited to 2-year-old horses, but race officials reversed that policy and allowed Lasix to be used in all races this year. The racehorse industry in North America is divided over the issue, with proponents of the diuretic arguing that Lasix protects horses’ health and improves performance, and opponents saying that permitting the drug is marring the sport’s good name.

Recent research by Paul Morley, a CSU professor in the Department of Clinical Sciences and one of the foremost experts on Lasix and EIPH,  provided important new information to stakeholders in the debate. Morley is part of a long-standing collaborative group that has published three new papers in Equine Veterinary Journal that address the effects of EIPH on performance as well as the efficacy of Lasix in controlling the condition.

In the first study, Morley and his co-authors studied EIPH in 1,000 racehorses, and showed that the condition has detrimental effects on their ability to perform as elite athletes. However, in another study that followed the lifetime racing careers of more than 700 horses, the research group was unable to find an association between EIPH and the number of races the horses were able to run or their earning potential, except in the most extreme form of the condition. In the third project, Morley and his research team examined existing studies on Lasix and concluded that there is high-quality, albeit limited, evidence that Lasix is effective in reducing the incidence and severity of EIPH in racehorses. The finding supports the results of his team’s landmark 2009 clinical trial on Lasix.

“Dr. Morley is very highly regarded worldwide,” said Dr. Thomas Tobin of the Gluck Equine Research Center at the University of Kentucky. “Everything he does carries significant weight because of the longtime recognition of his research and the quality of his work.”

“These studies build on our earlier work to provide horsemen and regulators with the evidence they need to inform the highly charged debate about EIPH and Lasix,” added Ken Hinchcliff, Dean of the Faculty of Veterinary and Agricultural Sciences at the University of Melbourne, Australia, and one of Morley’s longtime collaborators on the studies. “Our international team has explicitly addressed the key issues facing racing around the management of EIPH.”

Despite the controversy surrounding the issue, Morley said he and his fellow researchers don’t have a horse in the race, so to speak; they are simply trying to provide independent, unbiased information so that ongoing discussions about Lasix are based on sound facts.

Morley acknowledged that there is much more research to be done, since the long-term effects of EIPH and Lasix on the wellbeing of horses are still unclear.

“We want to continue providing high-quality evidence for the decision-makers, to inform the debate,” he said.

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