by Frank Angst

Race-day application of Salix benefits Thoroughbred health and welfare by reducing exercise-induced pulmonary hemorrhage, according to a study that could influence international policy.

The comprehensive study of Salix, trade name of the diuretic furosemide and formerly marketed as Lasix, included 167 Thoroughbred horses studied during racing conditions in South Africa in 2007. Its results will be published in the Journal of the American Veterinary Medical Association.

“The data in the study provides the most reliable information to guide the highly politicized debate over use of furosemide in horses," said Kenneth Hinchcliff, Ph.D., University of Melbourne dean of the faculty of veterinary science and study co-author.

Other co-authors in the study, titled “Efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses,” were Paul Morley, Ph.D., of Colorado State University; and Alan Guthrie, Ph.D., University of Pretoria in South Africa.

While Salix is widely used on race day in the United States, a national and international debate has continued over its effectiveness in preventing pulmonary bleeding, which is the reason it is used.

“To date, there has been only a limited amount of high-quality evidence--and none matching the quality of this study--to inform the debate,” Hinchcliff said. “We know that furosemide is associated with improved performance, and that exercise-induced pulmonary hemorrhage markedly affects race performance. But we didn't know the answer to the third--and most important--leg of the trifecta: Whether furosemide is effective in treating EIPH. We now know.”

The results of the study could influence policy of the International Federation of Horseracing Authorities Advisory Council on Prohibited Substances. Except for the U.S., some South American countries, and parts of Canada, furosemide use is prohibited on race day.

In the study, each horse raced twice, once after receiving furosemide before the race and once after receiving a placebo. The results showed that horses were three to 11 times as likely to have EIPH after placebo administration as they were after administration of furosemide. In addition, about two-thirds of the horses that had EIPH after administration of the placebo had a reduction in EIPH severity when treated with furosemide.

“This study design is similar to those used to test the efficacy of treatment in human medicine,” Morley said. “To date, such studies have been uncommon in veterinary science, and we believe that our study is unique among studies of drug efficacy in racehorses under conditions of racing. The rigorous approach to study design resulted in a very clear result.”

The study very likely will influence furosemide policies throughout the world.

“It is likely that racing jurisdictions will reconsider, in one way or another, their position on the use of furosemide,” said the study’s authors. “However, the decision to allow or disallow the use is based on the balance of a number of factors, and resolution of this complex situation will take some time.

“The challenge will now be for countries such as England, Hong Kong, Australia, and South Africa that do not currently permit race-day use of furosemide. The challenge that they will face is balancing the animal-welfare aspect of being able to prevent or reduce the condition against the imperatives for drug-free racing. Additionally, instituting race-day administration of furosemide would be a significant added expense to racing.”

The study received grants from the Grayson-Jockey Club Research Foundation, the Racing Medication and Testing Consortium, and racing interests in South Africa.

Frank Angst is senior writer for Thoroughbred Times