The Horseracing Integrity and Safety Authority (HISA) has approved funding for three 18-month-long studies on the use of furosemide, also widely known as Lasix, on racehorses. Washington State University received more than $370,000 to study the drug's impact on exercise-induced pulmonary hemorrhaging (EIPH) in racehorses.
Furosemide is a diuretic that reduces the severity of EIPH, which causes horses to bleed in their lungs when galloping at high speed. Racehorses' careers can be limited if this bleeding becomes too severe. Though usage waivers are given as research is being conducted, most major events, including the Kentucky Derby, ban race-day use of furosemide. EIPH may also affect horses that participate in barrel races, as well as hunter jumpers and other equine sports.
WSU's research into furosemide is led by Warwick Bayly, an equine veterinarian at WSU's Department of Veterinary Clinical Sciences. Bayly and his team plan to analyze data from about 30,000 racehorses, focusing on video recordings and examinations of the horses' tracheas. They're also tracking the performance of about 2,000 horses with known levels of EIPH for the next 12 months to also assess the impact of EIPH severity on racing careers.
Additionally, the study will look at horses that raced before the furosemide ban from 2015 to 2019 and after the ban was established by HISA from 2021 to 2025.
"I don't make the rules but some people are hoping that HISA may decide to allow furosemide to be used," Bayly says. "Whether or not it will change, I don't know."
HISA will review the findings and is expected to make a decision on the use of furosemide in May 2026.