Furosemide debate continues

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The drug furosemide has been at the epicenter of the controversy over drugs used in horse racing, or more specifically, drugs that are administered on race day.

Dr. Rick M. Arthur
Dr. Rick M. Arthur

Furosemide has been used in racing at least since the 1960s, although it was unsanctioned at the time. The California Horse Racing Board was one of the first commissions to approve the drug in the early 1970s. Back then, it was used to treat high blood pressure—that is why it was prescribed for humans at the time—but its effect on reducing exercise-induced pulmonary hemorrhage and its performance-enhancing effect also weren’t lost on trainers, according to Dr. Rick M. Arthur, Racing Medication and Testing Consortium officer and equine medical director for the California racing board. He spoke about EIPH during the “Current Controversies in Equine Practice” session at the American Association of Equine Practitioners’ 59th Annual Convention, held Dec. 7-11, 2013, in Nashville, Tenn.

“The reality is all horses bleed,” Dr. Arthur said, adding that there are a number of theories about the cause of EIPH. “I’m not going to get into the theory of why horses bleed, which is a fascinating physiological phenomenon. The bottom line is the horse’s heart is beating so rapidly that the left side of the heart doesn’t have time to fill, so blood builds up in the lung. Whatever the cause, increasing the blood pressure in the lung leads to breaking blood vessels in the lung.”

In 1980, Dr. John Pascoe coined the term “exercise-induced pulmonary hemorrhage” at the AAEP meeting that year. He defined the condition a year later in the American Journal of Veterinary Research. Since then, nearly 200 papers on PubMed have discussed EIPH.

In the early 1980s, people were still skeptical as to whether furosemide worked at all, but that was put to rest with the paper by Dr. Kenneth W. Hinchcliff “Efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses” (J Am Vet Med Assoc 2009;235:76-82), which showed furosemide is effective at reducing EIPH.

The Breeders’ Cup is funding work by the American College of Veterinary Internal Medicine to develop a consensus statement on exercise-induced pulmonary hemorrhage.

Dr. Arthur also noted, “The fact of the matter is horses run faster with Lasix, and it’s one of the issues I’m surprised people don’t realize. People forget that furosemide has a pretty profound effect on the cardiovascular and pulmonary systems.”

He pointed to the paper “Effect of furosemide on performance of Thoroughbreds racing in the U.S. and Canada” (J Am Vet Med Assoc 1999;215:670-675), which found that the typical horse in a 6-furlong race will run faster when on the medication than when not.

That study, Dr. Arthur said, inspired the RMTC to change its rules on furosemide. Before, the drug could be administered only when bleeding could be seen, but thereafter, the RMTC recommended eliminating that requirement. Nowadays, 98 percent of horses that race are given furosemide. The Jockey Club and some breeders advocate banning the administration of medications to prevent pulmonary hemorrhage because of their perceived performance-enhancing effects.

“The international racing industry doesn’t use Lasix (to race), and their horses are every bit as healthy as ours. And I think that’s where we’re going to be,” Dr. Arthur said, referring to the U.S. He said that more-restrictive regulations on the use of drugs in racing will focus not just on furosemide but also on phenylbutazone and other nonsteroidal anti-inflammatory drugs. “I think that’s what the public will be demanding, and I think we need to prepare for it,” he said.

Currently, the AAEP supports the use of furosemide on race day. That said, the AAEP petitioned the American College of Veterinary Internal Medicine in 2013 to develop a consensus statement on EIPH. It will focus on three questions: Is furosemide performance-enhancing? Are there alternatives? Is use of furosemide a welfare issue? The statement is expected to come out in 2015. The Breeders’ Cup is funding the endeavor.

Dr. Arthur said other research efforts should focus on a fundamental question: Does the use of furosemide alter the long-term pathological changes associated with EIPH?

Advocates of horse-racing reform say additional substances will be considered for inclusion in the schedule of controlled medications, on the basis of AAEP and RMTC recommendations. Other reform plans may be modified, depending on future scientific research and development.