Racing rule changes regarding the pre-race administration of furosemide (Salix, commonly called Lasix) appear unlikely following the results of a pair of studies that assessed the diuretic used to prevent exercise-induced pulmonary hemorrhage.
A study led by Dr. Heather Knych of the Ken L. Maddy Equine Analytical Chemistry Laboratory at the University of California-Davis examined the efficacy of Lasix in preventing or reducing the severity of EIPH if administered 24 hours before a race, as opposed to the current four-hour standard. According to results outlined at the American Association of Equine Practitioners convention in late November, the study determined the four-hour timeframe was the most effective for reducing the severity of EIPH.
Another Lasix study, led by Dr. Warwick Bayly, found some potential for a low dosage of Lasix 24 hours out, combined with controlled access to water in reducing EIPH.
Racing Medication and Testing Consortium executive director Dionne Benson said there has been no discussion at this point on the outcome of the studies. She said the RMTC is committed to working toward putting the current standard of third-party Lasix administration four hours before the race in place in all racing states.
As one might expect, the results of the study were viewed differently by groups on differing sides of the race-day Lasix issue.
The Jockey Club, which supports federal legislation that would end race-day Lasix, notes that the differences Dr. Knych's study found between the four-hour and 24-hour administration times were in red blood cell counts in bronchoalveolar lavage fluid. The study noted that the EIPH scores did not appear to correlate with the results of RBC counts from the BAL in this study.
"We found it interesting, that when horses were subjected to the most objective manner of determining EIPH, the scientists found no statistical difference between four- and 24-hour Lasix," said Jockey Club executive vice president and executive director Matt Iuliano. "We also found it interesting that the study confirmed that the majority of Thoroughbreds simply do not have sufficient clinical signs to even require Lasix in the first place."
The Horsemen's Benevolent and Protective Association pointed to the study's outcome as support of the current four-hour administration time. National HBPA CEO Eric Hamelback said going into the study that he was not opposed to changing the standard, if science supported the idea of pushing back the administration time, but he believes the outcome supports the current approach.
"Professional horsemen and veterinarians look at the use of Lasix as pro-horse," Hamelback said. "We look at its use as a positive in equine health and welfare and we want what's best for the horse. Lasix is beneficial."
Iuliano noted that the study only found EIPH—in this case defined as endoscopically visible hemorrhage of grade 1 or higher, in 26% of the horses post-race.
"This would certainly explain why the Europeans race so successfully without it," Iuliano said. "This is further demonstrated when studying the lifetime careers of Thoroughbreds, which revealed that EIPH produced no effect on their success on the racetrack."
Hamelback noted that owners and trainers in the United States have the option of racing their horses without race-day Lasix.
"The use of Lasix is not required. It's a choice," Hamelback said. "In the recent Pegasus World Cup (Invitational Stakes, G1), connections had the option of a seven-pound allowance if they raced without it, but all the horses started on Lasix. That's because they each decided that receiving Lasix was in the best interest of their horse. In the U.S. we have that choice."
Funding for the studies was provided by Grayson-Jockey Research Foundation, the AAEP, and a number of tracks.