A new study released Monday by Breeders' Cup officials clouds the picture on whether Lasix helps or hurts racehorses.
According to data collected at California's Santa Anita Park during the two-day Breeders' Cup World Championships in November, horses that ran on the drug furosemide — known as Lasix or Salix — were more likely, not less likely, to bleed in their airways.
"This is not what I was expecting to find," said Dr. Nathan Slovis of Hagyard Equine Medical Institute in Lexington, who led the study of 2-year-old horses. "I was expecting animals that were not given furosemide would have an increased score on (exercise-induced pulmonary hemorrhage). That's what I expected to find. We did not find that in this small group."
In 2012 and 2013, the Breeders' Cup did not allow 2-year-olds in its races to use the anti-bleeder medication, but horses in other races on the cards those days could use it.
Slovis and the veterinary team asked owners and trainers of all 78 horses racing those days to let them conduct an endoscopic exam, putting a camera down each horse's windpipe, to check for bleeding.
"The goal was to document occurrence of EIPH," Slovis said, referring to exercise-induced pulmonary hemorrhage.
Researchers were allowed to scope 55 horses. They graded the level of bleeding by standard measures used by veterinarians.
"The furosemide-treated horses had proportionally more horses with higher scores," according to the study results.
"We had no thoughts that this would be definitive," said Breeders' Cup board chairman William S. "Bill" Farish Jr. "We were surprised by the results and hope it will lead to more cooperation (on future studies). Very interesting and very surprising."
In a conference call with reporters, Slovis cautioned against reading too much into the results.
"I can't stress this enough: It was not: 'Is Lasix good; is Lasix bad?' The question was: 'Are we doing any harm to racing without Lasix?'" Slovis said.
The answer appears to be no.
The proportion of horses that bled significantly was greater among horses treated with furosemide (71 percent, or 10 out of 14) than untreated horses (37 percent, or 15 out of 41), according to the study.
The question grew out of a movement in Thoroughbred racing in recent years to ban the use of furosemide, in part to counter public perception that racing relies on performance-enhancing drugs to the detriment of the horses and jockeys.
The results appear to counter a South African controlled study that found furosemide reduced bleeding, but Slovis said the two studies are so different that comparing them is "apples and oranges."
The Breeders' Cup study raises as many questions as it answers, said Breeders' Cup president and CEO Craig Fravel.
"I want to thank Dr. Slovis and the Hagyard Equine Medical Institute for their efforts as well as the horsemen who agreed to participate in the study," Fravel said in a news release. "Beyond the stated conclusions, which, given prevailing sentiment, are both striking and surprising, this observational study reinforces our commitment to investing in research focused on EIPH. We urge the racing industry to reflect thoughtfully on the results and to support further scientific inquiry into this and other critical areas."
The Breeders' Cup financed the study, Fravel said.
Slovis said researchers don't know why the results were the opposite of what was expected. Perhaps it was because the horses included were elite athletes, racing at the top level in the peak of conditioning.
He said that the study size was small, that participation was voluntary and that with the ban on furosemide known well in advance, horse owners might have excluded horses more likely to bleed.
Another intriguing finding: Horses that were on Lasix did not appear to run faster than those not on Lasix. Handicappers often expect horses — particularly those racing for the first time on furosemide — to do better.
Looking at times and distance raced, Slovis said, showed no real difference.
He said veterinarians are gathering additional data that might shed some light on some of the questions raised, such as whether any of the horses had raced previously on Lasix. The vets also did not look at other medications the horses had been given; use of non-steroidal anti-inflammatory drugs could be linked to an increase risk of bleeding.
Slovis said the next step would be to widen research to look at horses running at lower levels.
He said the vets are thinking about how to enhance future studies.
"It's so tough with a small group of horses," Slovis said. "We're going to need a large group of horses to get the statistics correct and get some meat into this.
"We're going to need lots of tracks, hundreds of horses, and some horses racing on Lasix and then not racing on Lasix. It's a lot to wrap your arms around."
The Breeders' Cup prohibited the use of furosemide in 2-year-olds and planned to phase the ban into other horses, but that plan was halted this year after the Breeders' Cup concluded it didn't have the authority to force other racing jurisdictions to impose the ban.
The Kentucky Horse Racing Commission also passed a phased-in ban on the use of furosemide to begin next year with 2-year-olds in stakes races, but the rule was never filed with the state Legislative Review Commission, so it never took effect, said John Ward, executive director of the commission.
Ward said Lasix regulation probably was going to resurface in Kentucky. "The industry hasn't forgotten about it," he said. "We just decided to get more information."
Janet Patton: (859) 231-3264. Twitter: @janetpattonhl.