With the Horseracing Integrity and Safety Authority's Anti-Doping and Medication Control program now in full swing, many state racing commissions have submitted requests for an exemption from national rules regarding furosemide use.
The new regulations that went into effect May 22 would prohibit the race-day use of furosemide (commonly referred to as Lasix) in all Thoroughbreds, going a step farther than states that have already prohibited its use in 2-year-olds and stakes runners. The federal law creating HISA does, however, permit states to seek up to a three-year exemption from enforcement of these rules for horses aged three and up and not competing in stakes.
At the time that a handful of jurisdictions first voted for a partial Lasix phaseout, many horsemen and fans fretted about whether the removal of the drug from pre-race administration could have unintended humane impacts on horses.
“There was a lot of lay literature statements regarding how badly the 2-year-olds were going to bleed and the most emphatic statements from some people were that 2-year-olds were going to die because of massive exercise-induced pulmonary hemorrhage [EIPH],” said Dr. Warwick Bayly, professor of equine medicine at Washington State University.
Bayly and colleague Dr. Macarena Sanz were recruited to study the issue in 2020 and 2021. A variety of stakeholder groups, including seven or eight racetracks and the Breeders' Cup, funded the use of endoscopies on horses running in races where race-day furosemide was prohibited and those whose state commissions had not yet tightened those rules. The state of Maryland made post-race endoscopies mandatory, giving the research team an even larger pool to work with.
Bayly said the study is unique in terms of its volume of data and also its geographic variability, with scopes coming in from horses coast to coast and from near the Canadian border down to Florida. Many other studies on furosemide use in the United States and elsewhere have been limited to racetracks with similar environmental conditions.
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Bayly and his team are still analyzing the massive cache of data they gathered between 2020 and 2021, with plans of publishing multiple papers in peer-reviewed journals with different types of analysis. Two papers remain under review, but Bayly was able to share a few of his key takeaways from his data on 2-year-old runners with the Paulick Report.
–When limiting the data to 2-year-olds, Bayly had over 1,000 scopes coming from horses at 15 different tracks. About half came from Maryland, because that state had mandated post-race scopes to check for evidence of bleeding from EIPH.
–Because so many tracks are in states that had restricted furosemide use from 2-year-old runners at the time of the study, only about 12 percent of the 2-year-olds scoped had been running on furosemide, which could somewhat limit application of the findings (although statistical analysis is designed to account for differences in sample sizes).
–There is no evidence from this research that 2-year-olds, as a group, are at different risk of EIPH from their older counterparts.
“As far as we can tell, 2-year-olds don't bleed any less or any more than a population of Thoroughbreds from two to four or five years of age,” said Bayly. “A significant number of horses were scoped after they had their first race start, and as I recall, about 60 percent of them had signs of EIPH. The notion they don't bleed as 2-year-olds or that they bleed less as 2-year-olds was not substantiated. I don't think they bleed any less severely or any more severely than the general population.”
–Data on stakes horses did suggest that accumulation of race starts did make individuals more likely to experience EIPH. The tipping point seemed to be around 30 starts, which corresponds with previous research on the topic, but Bayly said this doesn't account for the impact of breezes, which may also have a cumulative effect on a horse's chances of developing EIPH.
–Furosemide does not totally prevent bleeding.
“The notion that furosemide stops the bleeding and they have zero EIPH is absolutely not true,” he said. “We had horses on Lasix with Grades 1 and 2 [of EIPH on endoscopy, which is on the low end of a scale that runs from Grade 0 to Grade 4].”
Bayly said the proportion of horses that had Grade 3 and Grade 4 bleeding on scope was essentially the same between Lasix and non-Lasix groups.
–Less than 10 percent of 2-year-olds experienced severe EIPH, regardless of their furosemide status.
–Interestingly, the scope results from Maryland showed a lower incidence and severity of bleeding than other geographic groups. Bayly theorized this may be related to the fact scopes were mandatory there, whereas in other places, trainers were asked to participate voluntarily. It's possible people are more likely to volunteer to have their horse scoped if they already suspected there may have been bleeding from EIPH, and are less likely to request a scope if they have reason to think the horse either didn't bleed at all or bled very little.
There's also some question about what constitutes true EIPH. Bayly has seen variability in scoping results depending on the length of the endoscope, and the amount of time between exercise and scoping. He has also seen horses who had no sign of blood in the trachea who did have lots of red cells in a lung lavage. So, while endoscopy is the gold standard for checking for EIPH, it's not the be-all and end-all.
–More broadly, there were differences from track to track in the likelihood that a horse would show signs of EIPH on scoping independent of furosemide status. Bayly said the reasons for this are not clear, and further research is needed to identify what these influences on EIPH may be. He cautioned that it may not be something as simplistic as air quality rating in a given region, since so much individual variation could be present from barn to barn or even stall to stall at a racetrack.
Overall, Bayly said, this study provides more data on the topic of furosemide and EIPH than previous research, but it's not going to provide clear, black-and-white answers with regard to ideal regulation.
One thing he does feel pretty confident about from the research:
“If you're worried about EIPH from the perspective of interfering with performance, we found it had some impact on performance just like what's been shown before, but only on really severe EIPH cases,” he said. “Less than 10 percent of horses had any association with not running well as a result of EIPH.”
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