The results of a recent study have revealed that a drug commonly used to treat exercise-induced pulmonary hemorrhage (EIPH) is not as effective as veterinarians previously thought.

Belinda M. Buchholz, BS, a second year veterinary student at Washington State University, and colleagues set out to determine if aminocaproic acid (ACA), a drug that helps blood clot, decreases the amount of bleeding occurring in the respiratory tracts of horses with EIPH.

Exercise-induced pulmonary hemorrhage causes bleeding in the lungs during strenuous exercise. Clinical signs of EIPH in a horse range from a reddish tinge in the horse's mucus to a severe nosebleed. Veterinarians are generally concerned that repeated episodes of EIPH cause inflammation and scarring that reduces the elasticity of the lungs and makes it harder for the horses to breathe optimally during high-speed exercise.

"If the horse can't take in as much air, it takes in less oxygen and fatigues faster and performs less well," Buchholz said. "A single episode of EIPH is unlikely to end a career in a horse, but if repeated episodes occur, the length of a horse's career as a successful athlete may be shortened."

"We have to focus our efforts to deal with EIPH on medications that might reduce the amount of bleeding associated with each hemorrhagic episode," said Warwick Bayly, BVSc, MS, PhD, Dipl. ACVIM, a co-author on the study and the provost at Washington State University's veterinary school. "We are fooling ourselves if we think we can truly prevent bleeding.