Exercise-induced pulmonary hemorrhage, or EIPH, is still without a known cause. However, this disorder is well-known to affect all racehorses at some point during their racing careers. It has also been observed in steeplechasers, polo ponies, and other equine athletes, as well as in draft horses that must pull heavy loads on a regular basis.

Bleeding and Its Effects on Horse Health

Although no one has been able to zero in on why horses bleed following strenuous exercise, it’s been theorized that the high pressure in a horse’s body during intense exercise can cause the rupture of some capillaries in the lungs.

Two aspects of EIPH that are known are that lung damage occurs with each episode of bleeding and bleeding episodes can result in fatal pulmonary hemorrhage. Although it has not been proven, many horse owners have speculated that the cumulative lung damage caused by EIPH impairs racing performance.

Lasix as an EIPH Prevention Option

Lasix, also marketed as Salix, is a popular pharmaceutical that’s used to prevent EIPH in racehorses. Also known as furosemide, this drug is administered by a veterinarian approximately four hours before a race. Lasix also has diuretic properties, causing horses to lose large amounts of fluid through urination before a race, which improves their speed.

Lasix is widely accepted as an effective option for the prevention of EIPH in horses racing in North America. However, this controversial drug has been banned not only in a growing number of countries but also in a growing number of states because of its ability to mask the presence of illegal performance drugs in a horse’s system.

The unfortunate reality is that the diuretic properties of Lasix can cause a horse to become dehydrated, decrease their blood calcium levels, and cause electrolyte imbalance.