Exercise-induced pulmonary hemorrhage (EIPH) plagues many racehorses, with up to 75% of Thoroughbreds affected by this condition. Despite the relatively widespread use of furosemide (Lasix or Salix), this medication does not actually treat or cure EIPH. Instead, furosemide administration reduces EIPH â€œscores,â€ which means affected horses bleed less during exercise when they receive furosemide.
â€œEIPH occurs during strenuous exercise due to increased pressure in the small blood vessels in the walls of the horseâ€™s lungs. As a result, blood abnormally enters the lungs, which as one might imagine, decreases a horseâ€™s ability to perform in competition,â€ explained Laura Petroski, B.V.M.S., a veterinarian for Kentucky Equine Research (KER).
According to a recent study*, timing of furosemide administration greatly impacts efficacy of furosemide and therefore athletic performance.
â€œRace-day medication rules vary between racing jurisdictions. North America typically allows administration of furosemide on race day, usually up to 4 hours prior to post time. Other jurisdictions do not allow any race-day medications,â€ Petroski said.
Anecdotal evidence suggests furosemide is equally efficacious when administered 24 hours before post time (complying with international race-day medication rules) compared to 4 hours. If this is true, then no concerns surrounding furosemide administration and race-day performance would exist.
â€œUnfortunately, the study by a group of researchers from the School of Veterinary Medicine at the University of California, Davis, demonstrated otherwise,â€ noted Petroski.
Specifically, the research team found that EIPH scores were lower in horses receiving furosemide 4 hours prior to post time compared to 24 hours. The EIPH scores referred to in the study use a standardized scale ranging from 0-4, where 0 refers to no blood observed in the main airways and 4 indicates multiple streams of blood identified on endoscopic examination (â€œscopingâ€) covering 90% of the tracheal surface.
The researchers concluded that EIPH was not altogether prevented regardless of whether furosemide was administered 4 or 24 hours prior to racing. Further, administration 24 hours before racing does not appear as effective as when horses receive furosemide 4 hours prior to competition.
â€œHorses receiving furosemide lose valuable electrolytes in their urine. To replenish those losses, KER formulated an electrolyte product called Race Recovery. This supplement was specifically designed for horses treated with furosemide to ensure complete, optimally timed electrolyte replacement. In addition to sodium, chloride, and potassium, Race Recovery includes highly digestible forms of calcium and magnesium,â€ said Petroski.
*Knych, H.K., W.D. Wilson, A. Vale, et al. Effectiveness of furosemide in attenuating exercise-induced pulmonary haemorrhage in horses when administered at 4- and 24-hours prior to high speed training. Equine Veterinary Journal. In press.