When horses received furosemide four hours before exercise, 93% had a zero EIPH score one hour post-exercise versus 60% when it was given 24 hours before exercise. | Photo: Anne M. Eberhardt/The Horse

Under the pending Horseracing Integrity Act of 2017 (HR 2651), race-day administration of furosemide might be banned. This bill aims to improve the integrity and safety of horse racing by requiring a nationwide uniform anti-doping and medication control program to be developed and enforced by an independent horse racing anti-doping and medication control authority. Concerns exist that race-day administration of furosemide might mask other substances that have been given illegally.

In anticipation of this legislation, researchers from the University of California, Davis, looked at furosemide’s ability to reduce EIPH in Thoroughbred racehorses when administered 24 hours vs. four hours prerace. Anecdotal reports suggest that administering the drug 24 hours prerace might be as effective as race-day administration in decreasing EIPH severity. Associate professor Heather Knych, DVM, PhD, Dipl. ACVCP, presented their findings at the 2017 American Association of Equine Practitioners, held Nov. 17-21 in San Antonio, Texas.

For their study, the team used 15 client-owned Thoroughbred racehorses, both male and female, ages 2 to 4. the researchers didn’t know the EIPH status of each horse. They randomly assigned horses to one of three treatment groups: 250 mg of intravenous (IV) furosemide 4 hours before exercise, 250 mg of IV furosemide 24 hours before exercise, or 5 mL of 0.9% IV saline as a control. They restricted the horses’ water access four hours before -a five-furlong simulated race on either a synthetic or dirt track. All horses underwent a two-week washout period before moving to the next treatment, so that all horses received all treatments over the course of the study