01/31/2018 3:10PM

Study shows Lasix more effective at four hours than 24


A limited study comparing results of the administration of the regulated anti-bleeding medication furosemide on horses four hours prior to exercise and 24 hours prior to exercise has indicated that the drug is not as effective at the 24-hour mark.

The study, which was led by a prominent equine researcher, Dr. Heather Knych of the Ken L. Maddy Equine Analytical Chemistry Laboratory, compared the results of the administrations of the diuretic on 15 horses and found that horses scored lower on a scale evaluating the severity of bleeding when the horses were administered the drug four hours prior to exercise compared with 24 hours prior. In the United States, racing states allow for the drug to be administered four hours prior to a race.

The results are a setback for proponents of measures to eliminate rules in U.S. racing states allowing for the raceday use of furosemide, more commonly known as Lasix. Critics of raceday Lasix use began pushing for studies to test the 24-hour administration time several years ago, citing what they contended were anecdotal reports of the administration of the drug in countries where raceday Lasix use is banned.

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Funding for the study was provided by The Grayson-Jockey Club Foundation, the American Association of Equine Practitioners, a number of racetracks, and a horsemen’s organization. The funding organizations have a range of opinions about the raceday use of Lasix, including both sides of the debate.

Knych and her research team performed endoscopic exams and broncho-alveolar lavage, which collects fluid samples from lung tissue, in order to rate the bleeding of the horses in the study. Although the study noted that furosemide was not entirely effective at preventing bleeding in racehorses during exercise, it did conclude that horses administered furosemide four hours prior to a race had lower bleeding scores on a commonly used scale measuring bleeding severity and lower red-blood cell counts in the bronchial samples.

“There was a statistically significant difference in EIPH” – exercise-induced pulmonary hemorrhage – “scores between the four-hour and 24-hour furosemide administrations,” the study said.

Late in 2014, The Jockey Club, which is currently leading an effort to pass federal legislation that contains a provisions banning the use of furosemide on race day, began approaching racing commissions and groups seeking funding for a study that would examine the effects of administering Lasix 24 hours prior to race time on as many as 100 racehorses. The organization was hopeful that the results would show that the drug was at least as effective at the 24-hour mark as four hours, which would give supporters of a raceday ban a foundation for arguing for a 24-hour prohibition.

Critics of that proposal claimed there was no scientific basis for believing that the drug could be equally effective at the 24-hour mark.