Lasix, science, and welfare: when the debate outweighs the evidence

Prominent trainers and the National Horsemen's Benevolent & Protective Association published a letter in favor of continuing the use of the diuretic in the United States; HISA holds the decision in its hands

The debate over furosemide has returned to the center stage in the United States, but this time with a concrete countdown. The letter that ignited the discussion was signed by heavyweight trainers such as William I. Mott, Chad Brown, Mark Casse, Jena Antonucci, and Ron Moquett, along with Eric Hamelback, CEO of the National Horsemen’s Benevolent & Protective Association, representing owners and trainers from coast to coast.

The core issue is clear: the race-day use of Lasix and its continuity under veterinary supervision. Currently, the medication is prohibited in 2-year-old races and in stakes 48 hours before post time. However, the rest of the calendar operates under a 3-year exemption that allowed its use to continue while additional scientific studies were conducted.

That exemption expires next May 22. And there lies the critical point.

The Horseracing Integrity and Safety Authority (HISA) must submit the matter to a vote within its nine-member Board of Directors. As established by the Horseracing Integrity and Safety Act of 2020, to extend the exemption, the vote must be unanimous. If unanimity is not reached, furosemide will be prohibited under the 48-hour rule, which in practice would mean its total elimination on race day.

The argument of the signatories does not revolve around a corporate defense, but rather a medical issue: Exercise-Induced Pulmonary Hemorrhage (EIPH) is a documented condition, and furosemide—administered under strict protocols—reduces its severity. For many professionals, removing the tool without offering a validated alternative could impact equine welfare.

On the other side, the institutional argument points toward public perception, regulatory uniformity, and the evolution of the sport toward more restrictive international standards.

The letter explains the following: "If an Olympic sprinter bled in their lungs every time they ran a final, no one would call the treatment cheating. They would call it medicine. In racing, however, the discussion about furosemide—popularly known as Lasix—is often framed under the label of doping, a powerful word, emotionally charged and useful in the field of public opinion. The problem arises when rhetoric moves faster than veterinary science.

"At the center of the debate is Exercise-Induced Pulmonary Hemorrhage (EIPH), a condition extensively documented by the American Association of Equine Practitioners and multiple research centers. During maximum efforts, extreme cardiovascular pressures can cause the rupture of pulmonary capillaries. In many cases, the bleeding is microscopic; in others, repeated and progressive, it can lead to chronic inflammation, fibrosis, respiratory deterioration and, in rare situations, more serious consequences.

"The horse, unlike the human athlete, is an obligatory nasal breather. It cannot open its mouth to compensate for airflow when the demand increases. The intrathoracic pressure generated at racing speed is extraordinary. This vulnerability is anatomical, not a product of training or competitive ambitions.

"The primary pharmacological action of furosemide is diuretic: it reduces vascular volume and, with it, the pressure in the pulmonary circuit, mitigating the severity of the bleeding. It does not create speed. It does not manufacture stamina. It does not modify natural talent. Its function is to decrease a medical risk associated with extreme effort and, in many cases, contribute to the sporting continuity of the specimen.

"Eliminating the medication will not eliminate EIPH. What it will do is remove a therapeutic tool currently regulated under strict veterinary supervision. The scientific discussion about possible side effects on performance exists and continues, but there is a consensus that furosemide reduces the severity of pulmonary bleeding.

"Those who work in the sheds and stables before dawn know that the concept of welfare is not a slogan. It is a daily responsibility toward an animal that cannot express itself. In any athletic discipline—human or animal—preventive medicine is a pillar of responsible care. Policies must be based on evidence, not on symbolism.

"Public trust in racing is fragile and demands transparency, uniform rules, and rigorous control. The industry has evolved and will continue to do so if science offers safer and more effective alternatives. But decisions guided by optics rather than evidence can compromise what they seek to protect.

"Treating a pulmonary hemorrhage under veterinary supervision is not doping.

"It is responsible care.

"And in any reform, the horse—not the headline—must come first."

The vote is not simply administrative. It represents a turning point. If the Board opts not to extend the exemption, the change will be immediate and structural for the racing system in the United States. If the extension is approved unanimously, the debate will continue, but with additional time to deepen studies and consensus.

At its core, the discussion exceeds Lasix. It is about how to balance science, public perception, regulation, and animal welfare in an industry that seeks to sustain credibility without losing sight of the horse's physiology.

May 22 will not be just another day on the calendar. It will be a decision that can redefine daily practice at American racetracks and mark the sanitary course of modern turf.