Use of Furosemide for Exercise-Induced Pulmonary Hemorrhage in Racehorses

Below is a letter to the editor from Drs. Kenneth W. Hinchcliff, Paul S. Morley, and Alan Guthrie submitted to and printed in the Journal of the American Veterinary Medical Association (JAVMA, Vol. 239, No. 11, December 1, 2011 issue). Drs. Hinchcliff, Morley, and Guthrie conducted a study on the use of Lasix on racehorses in South Africa, and the resulting article describing their findings, "Efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses," was published in JAVMA, Vol. 235, No. 1, July 1, 2009.:

The International Summit on Race Day Medication, Exercise- Induced Pulmonary Hemorrhage, and the Racehorse, which was held June 13 and 14 in New York City and was convened by the American Association of Equine Practitioners, National Thoroughbred Racing Association, and Racing Medication and Testing Consortium, provided a welcome opportunity for the horse racing industry to identify issues around medication of racehorses.¹ Although a public report of the meeting has not yet been made available and we were not able to attend this invitation-only event, we understand that much of the meeting was given over to a discussion of the use of furosemide and the treatment of exercise-induced pulmonary hemorrhage (EIPH).

We believe that the debate and policy discussions about the use of furosemide and other medications should be informed by the best available evidence regarding efficacy and safety. Policies regarding officially sanctioned race-day use of furosemide were established in nearly all racing jurisdictions in the United States and Canada almost 30 years ago. Only recently has high-quality evidence become available to show that EIPH is a common disorder of racehorses that impairs performance during racing,² that the frequency and severity of EIPH are reduced by treatment with furosemide,³ and that race-day use of furosemide is associated with superior performance.⁴ Previous evidence was based on anecdotal reports, small studies, poorly designed studies, or studies that did not directly address the central issue of efficacy.

The current debate urgently requires information about the importance of EIPH to the long-term well-being of horses, the genetic and familial factors associated with EIPH, and the efficacy of alternatives to treatment with furosemide. This evidence should be obtained through well-designed studies that address these important questions in a manner that will provide meaningful answers.

Specific questions requiring clarification through well-designed studies include the following:

• Does EIPH adversely affect the long-term health and well-being of racehorses? We know of no studies that directly address this important concern. If EIPH is shown to adversely affect the long-term health and well-being of racehorses, then the development and use of methods to prevent EIPH or its adverse outcomes would be indicated. 
• Is there evidence of a familial predisposition to EIPH, and if so, what is the genetic study⁵ addressing only those horses with epistaxis, a severe and unusual form of EIPH. Whether there is a familial predisposition to or genetic basis for EIPH is unknown. 
• Are there treatments, other than furosemide, that are effective in preventing or ameliorating EIPH without having a separate effect on performance? If EIPH can be shown to adversely affect the long-term health or well-being of racehorses (which has not been demonstrated to date), then development of effective prophylactic or therapeutic interventions would be critical. 

These critical unknowns must be addressed before sound policies on management of EIPH that place the well-being of horses as the first priority can be developed and implemented. We encourage those individuals and groups involved in the racing industry to continue to support well-designed and focused studies that address issues of critical importance to the well-being of racehorses.

Kenneth W. Hinchcliff, BVSc, PhD, DACIVM
Faculty of Veterinary Science
University of Melbourne
Werribee, Australia

Paul S. Morley, DVM, PhD, DACIVM
Department of Clinical Sciences
College of Veterinary Medicine
Colorado State University
Fort Collins, Colorado

Alan Guthrie, BVSc, PhD
Faculty of Veterinary Science
University of Pretoria
Onderstepoort, South Africa

1. Larkin M. Horse racing eyes changes to stay relevant. J Am Vet Med Assoc 2011;239:1165–1167. 
2. Hinchcliff KW, Jackson MA, Brown JA, et al. Association between exercise-induced pulmonary hemorrhage and performance by Thoroughbred racehorses. J Am Vet Med Assoc 2005;227:768–773. 
3. Hinchcliff KW, Morley PS, Guthrie AJ. Efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses. J Am Vet Med Assoc 2009;235:76–82. 
4. Gross DK, Morley PS, Hinchcliff KW, et al. Effect of furosemide on the performance of Thoroughbred horses racing in the United States and Canada. J Am Vet Med Assoc 1999;212:670–675. 
5. Weideman H, Schoeman SJ, Jordaan GF. The inheritance of liability to epistaxis in the southern African Thoroughbred. J S Afr Vet Assoc 2004;75:158–162.