Furosemide is used to lessen the effects of a respiratory condition called exercise-induced pulmonary hemorrhage (EIPH), characterized by bleeding into the lungs or out the nose during exercise. | Photo: Anne M. Eberhardt/The Horse

One of the most controversial topics in Thoroughbred racing today is the race-day use of furosemide (commonly called Salix or Lasix). The drug is used to lessen the effects of a respiratory condition called exercise-induced pulmonary hemorrhage (EIPH), characterized by bleeding into the lungs or out the nose during exercise. In the midst of rumor and fact regarding the drug and the disease it treats, one professor offered an explanation.

During the well-attended Oct. 2 Veterinary Science Seminar “Furosemide and EIPH: Efficacy and Controversy: The American Horsemen’s Story,” held in Lexington, Ky., Thomas Tobin, MVB, MSc, PhD, MRCVS, Dipl. ABT, professor of pharmacology and experimental therapeutics at the University of Kentucky Gluck Equine Research Center, reviewed the relationship between EIPH, furosemide, and the racehorse.

EIPH and its Effects

Tobin relayed that the phenomenon now known as EIPH was first recorded in the literature in the late 1700s when it was identified as epitaxis (bleeding from the nostrils) after intense exercise, and a decrease in performance. But it wasn’t until the fiber-optic endoscope was invented in the 1970s that veterinarians found that up to 80% of racehorses had evidence of blood in their tracheas after a race.Later, veterinarians learned a bronchoalveolar lavage will show evidence of bleeding at the alveolar capillary level. The latter condition is now known as occult or internal EIPH