Vet Rebuts Casner: Lasix Use Does Not Compromise A Horse’s Musculoskeletal System

by | 10.16.2019 | 11:06am

Because Bill Casner has a deserved reputation as a fine owner and breeder of racehorses, I read with interest his article “Studies Show Some Therapeutic Medications Do More Harm Than Good,” appearing in the October 8, 2019, issue of the Paulick Report. I also did so because a significant part of my 30-year professional career as a racing equine veterinarian, president of the North American Association of Racetrack Veterinarians, and former member of the AAEP's Racing Committee has revolved around the appropriate use of therapeutic medications in racehorses. Further, I am a co-author of the groundbreaking AAEP White Papers regarding medication use in the racehorse and the treatment of racehorses in a pari-mutuel environment.

Therefore, I was surprised to see Bill Casner assert that the therapeutic use of Lasix (furosemide) significantly increased bone fracture rates in racehorses and caused fatal racing breakdowns. (I'll save my disagreement with his indictment of omeprazole and thyroxine for another time.)

Casner's cited support for the spurious conclusion that Lasix contributes to breakdown injuries of horses was a series of 12 human studies involving the use of loop diuretics (Lasix) by elderly men, post-menopausal women, children with heart defects, and others with underlying health and balance problems.

Human studies of that sort cannot be applied to condemn Lasix use in horse racing for at least two reasons. The human patients all had substantial chronic issues that compromised their health. And the human subjects generally were on long term daily doses of Lasix. Horses, on the other hand, receive Lasix on race day with the average horse racing six times a year, according to the Jockey Club Fact Book. Even quadrupling administration to account for Lasix use in training makes it highly unlikely that such low dosage can have any significant effect on bone structure.

But that aside, all the veterinary science that I know of demonstrates Lasix use does not compromise a horse's musculoskeletal system. For example, a study involving 5,000 racehorse necropsies at the University of California at Davis found no evidence of bone weakness (osteoporosis) even though an estimated 90% of the horses raced on Lasix.

The work of renowned experts confirms that finding. Paul S. Morley, DVM, Phd, DACVIM, professor of epidemiology at Colorado State University, a co-author of the seminal Lasix study (Efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses, J Am Vet Med Assoc 2009, 235:76-82), as well as several others, reported in a recent presentation that his research showed Lasix use does not cause bone weakening. (“Where Do We Go From Here? EIPH & Race-day Medication, A Scientist's Perspective.”)

Similarly, C. Wayne McIlwraith, BVSc, PhD, FRCVS, Dipl. ACVS, an equine orthopedic surgeon and a professor of orthopedics, stated in a recent seminar discussing racing fatalities that “there is no scientific evidence for Lasix promoting musculoskeletal injury.” (Bramlage, McIlwraith on Santa Anita: A Combination of Factors to Blame)

And regulatory veterinarians like Dr. Dionne Benson agree: “Of course we know that Lasix has nothing to do with breakdowns.” (Voss, The Whats and Whys Behind Santa Anita's Nightmare Spring Season, Paulick Report, 9/25/19)

By ignoring equine science in favor of select human studies Bill Casner gives meaning to the last words he wrote in his article –“A Little Knowledge Is a Dangerous Thing.” While we may disagree on whether it is good policy to permit race day Lasix there can be no legitimate scientific dispute about its safety.

Nicholas Meittinis, DVM, operates the Maryland Veterinary Group in Laurel, Md., and is president of the North American Association of Racetrack Veterinarians.

Twitter Twitter
Paulick Report on Instagram