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For most of the shared history of horses and humans, the fate of empires relied on the horses that carried their generals.  Battles as early as 3000 BC were fought in chariots, with mounted war horses coming in favor in 1350 BC.  Evidence of horse racing dates back as far as recorded history.  In 330 BC Philip II, father of Alexander the Great, entered a horse in a race in the Greek Olympics.  Upon winning the race, he struck a suitably silver coin to commemorate this historic human/equine event, promoting both his Royal self and his equine partner, as below.  And for the record, the name Philip means “friend of horses”. 





Flat racing, as we know it today, originated in England under the reign of Queen Anne (1702-1714) after the English Knights returning from the Crusades, brought with them fast Arabian horses.  The crossing of these Arabian stallions with the heavier English mare produced the first Thoroughbreds, with both speed and stamina, and the “Sport of Kings” was born.

From the chariot racing of ancient Rome to what we recognize as horse racing today, this sport has been popular since the beginning of domestication of the horse and remains a major economic engine providing millions of jobs, trillions in revenues for governments, entertainment, and billions of acres of preservation of green space.  While its position as the “Sport of Kings” remains in place across the rest of the world, in North America, the allure of watching and even owning one of the most elite of athletes is accessible to fans of a wide range of income levels.  The popularity of the North American Racehorse has been proven year over year by its success both on the race course and in the sales ring.

Competition for the entertainment and gambling dollar in North America has put pressure on the Racing Industry.  Some stakeholders have chosen to claim medication is responsible for every problem, downturn in the popularity of racing and every tragic event occurring in the industry rather than choosing to invest in good faith investigation of the real causes of the problems. Therapeutic medication for our equine athletes is more rigorously restricted than medication of human athletes or even bus drivers and pilots! No medication other than Lasix is permitted on race day, and the use of Lasix is highly regulated.  Standard drug testing for horse racing includes screening for over 2500 substances, including both performance enhancing drugs and run of the mill therapeutic medications, similar to the sorts of medications you may find over the counter in the drug store.  With this extensive testing program, only 0.6% of horses violate the highly restrictive medication regulations.  Only 0.04% of those samples were actually positive for substances that have the greatest chance of enhancing performance, with the remainder of the positive tests for therapeutic medications.  Yet, some groups and individuals are working to restrict such therapeutic medication from our precious athletes even further, targeting the people that are most concerned with the health and welfare of the horses. The movement to restrict therapeutic medication is simply not in the best interest these athletes - just as it would not be in the best interest of human athletes nor even any human being. Therapeutic medications are necessary for any number of conditions are essential for the health and welfare of many of our beloved cats and dogs. Horses are no less beloved by their connections. There are many medications that are not only beneficial; they are essential for the health and welfare of the equine athlete and Lasix is one of them. The following information will explain why this is true. The in-depth sections contain additional information and references as well as an excellent “white paper”, THE LASIX QUESTION, which was produced by the New York Thoroughbred Horsemen’s Association (NYTHA).



The first record of such bleeding is by the Elizabethan author and horse breeder Gervase Markam, who noted in one of his books on horsemanship in the 1500’s, in good Elizabethan English, that:

“Many horfes [efpecially young horfes] are often fubject to this Bleeding at the Nofe, which I imagine proceedeth either from the much abundance of Blood, or that the Vein, which endeth in that Place is either broken, fretted or opened.”

Markham was describing the long known “at the nostrils” post exercise presentation of blood, what we now know as Exercise Induced Pulmonary Hemorrhage, EIPH.  Horsemen had long suspected that horses bled into their lungs during exercise, but visualization of such internal bleeding required development of the fiberoptic endoscope. 

As long ago as the early 1700’s, when the foundation sires of the Thoroughbred breed were racing and breeding, EIPH was recognized as epistaxis, or bleeding from the nose. One of the most prolific sires, Bartlett’s Childers, was also known as Bleeding Childers for his propensity to bleed from the nose.  Bartlett’s Childers was unraced, but is distinguished by being the great, great grandsire of Eclipse, and represented in the pedigree of every modern day Thoroughbred.  It was only with the development of first the rigid endoscope in the early part of the 20th century, and then the flexible endoscope in the 1970’s, that it was discovered that a very high percentage of horses bleed internally following strenuous exercise to some degree. Therefore, what was obvious for centuries, epistaxis, became only the “tip of the iceberg”, accounting for only about 4% of the cases of EIPH.


​EIPH is hemorrhage that can occur in the lungs of animals, including horses, camels, greyhounds and even in top end human athletes during strenuous exercise. This hemorrhage occurs in polo horses, show and event horses, barrel racing horses and any other equine athlete participating in any endeavor where strenuous exercise is required. In racehorses, EIPH incidence is 50-95% with well over 90% of horses bleeding at some time in their careers and airway examination suggest that all racehorses experience some minor degree of EIPH. This hemorrhage occurs when the thin membrane between the capillaries and alveolar air sacs fails due to the pressure within the circulatory system of the lung.  The blood in the lungs along with the damage from the ruptured capillaries results in inflammation that heals with scarring, and the lungs lose their natural ability to expand and contract.  With each subsequent EIPH injury, the disease is progressive, and the scientific evidence has shown that the result in permanent injury to the lungs.  In most cases, the hemorrhage is slight, but as more capillaries fail, the bleeding can be marked, even, in rare cases, resulting in fatal hemorrhage.  In extreme cases, the bleeding from the lungs can be so extensive that blood can be seen coming out the nostrils as the horse runs.  In this extreme situation, the horse is in danger of faltering, thus endangering itself, its rider and other horses and riders.  In the past, before Lasix was used, horses have even died during this terrible event.  With the advent of using Lasix in horse racing, this catastrophic event has virtually been eliminated.


EIPH is due to stress failure of capillaries and subsequent lung tissue remodeling as a result of the very high pulmonary vessel pressures that occur during strenuous exercise. It remains one of the most researched conditions of the race horse.  The preponderance of the scientific literature has revealed the following:

1) When the disease is not controlled, a cycle of hemorrhage, inflammatory reaction and more hemorrhage is recognized

2) EIPH may occur at any age

3) Has not been established to be an inherited trait

4) Occurs with high frequency in all sexes



1) Bleeding from the nose (epistaxis) – recognized almost from the inception of the Thoroughbred breed in the 1700’s

2) Endoscopic examination of the respiratory tract, a procedure well tolerated by the horse.  Flexible fiberoptic endoscopes, developed in the late 1970’s, permit examination of the respiratory tract into the major bronchi to each lung.  All racetrack veterinarians carry a flexible endoscope, and this is the most common means of evaluation of both the upper airway and lungs of the horse.

3) Bronchoalveolar lavage fluid (BAL) collection involves injection of sterile fluid into the bronchi followed by collection of this fluid to be examined microscopically.  This procedure requires tranquilization in most horses, and is often not tolerated by the patient, rendering it less useful as endoscopy.





















Once EIPH has occurred, treatment is directed at controlling the inflammation, and clearing the blood and inflammatory debris from the lungs.  Some veterinarians prescribe antibiotics to prevent bacterial colonization of the blood, bronchodilators to aid in removal of the blood and even hyperbaric oxygen therapy to accelerate healing.  If severe enough, lung rest, such as restricting fast exercise is required during the healing process.

The best method of EIPH control is the pre-exercise administration of Lasix.  This therapeutic medication has been unequivocally shown to decrease the incidence and severity of EIPH. Veterinary medicine often lacks the sort of Gold Standard of research to clearly demonstrate effects using prospective randomized clinical trial, but in the case of Lasix, a study by Hinchcliff and others in 2009 has done exactly that.  Using this high quality of evidence, the authors showed that Lasix decreases incidence and severity of EIPH.  It is included in a consensus statement by the American College of Veterinary Internal Medicine (ACVIM), found HERE.  

No preventative for EIPH has been studied to the same extent as Lasix.  Many others have been tried, including medications that enhance clotting, improve capillary stability, or decrease blood clot reduction.  Of those medications, most have failed to demonstrate effectiveness.  Once it was discovered that the diuretic, Lasix, helps to prevent EIPH, some horsemen began to withhold water for up to 24 hours before racing or strenuous training.  There is no evidence that this practice is effective and could be considered inhumane.  Concerns remain high that this practice is in use in countries where Lasix cannot be used, and may be instituted in this country, if Lasix were to be prohibited. 




​It has long been rumored that the recently FDA approved diuretic was used to facilitate Northern Dancer’s victory in the 1964 Kentucky Derby.  A decade later, in 1974, the use of Lasix was legalized on race day for use in Maryland.  In 1976 a committee lead by Dr. Al Gabel of the American Association of Equine Practitioners (AAEP) reported to the National Association of State Racing Commissioners (NASRC) that Lasix “helped prevent epistaxis”, (bleeding from the nose), and that “in many cases it restores normal performance of horses which bleed”.  With the resounding support of the veterinary community, all states rapidly adopted a 3 to 4 hour Lasix rule, except for New York.  As the last holdout state, New York finally adopted the rule in 1995, and experienced a close to 80% decrease in its incidence.




















Lasix (Furosemide) is a short acting diuretic, or “water pill”, patented in 1959 and approved for use in 1964.   It is used most commonly for swelling or edema resulting from heart failure, liver or kidney disease, as well as high blood pressure.  It is on the World Health Organization’s “List of Essential Medicines”-the most effective and safe medications needed in a health system. Tens of millions of people take this medication daily. Lasix has been used for horses with EIPH for over 40 years and approximately 90% of the horses running in North America are given this therapeutic medication before a race. Lasix is universally recommended by every major US veterinary organization for the health and welfare of racehorse.

Lasix is a short acting diuretic effect whose peak effect occurs at 30 minutes, with a return of the urine to pre-Lasix concentrations by 2 ½ hours.  It decreases right atrial blood pressure up to 3 hours and lowers the pulmonary capillary pressure up to 4 hours.  It must be administered on the day of the race or strenuous exercise, no more than 4 hours before the event for effect. Dehydration due to Lasix is minimal and return to normal values occurs even before the strenuous exercise occurs.



Diuretics are a great concern as masking agents in human drug testing.  Almost all drug testing in humans is performed in urine, and any medication that causes the urine to be dilute will dilute any prohibited substances, possibly to the point of making them undetectable.  State horse racing regulators shared this concern at the time Lasix use was adopted.  This was addressed early by the racing industry by establishing a 4 hour rule, whereby Lasix was administered at 4 hours before racing, a full 1 1/2 hours after the diuretic effect had abated.  This procedure was validated in the early eighties and adopted by all state racing jurisdiction, and eventually New York in 1995. Lasix was strictly regulated by the states and has evolved to the point that Lasix is now in most states administered by veterinarians employed by the regulatory entities rather than the private practitioners that normally take care of the health needs of the racehorses.  In addition to this 4 hour rule, in the last 5 to 10 years, drug testing in horses has switched from a urine based system, such as that used in human athletes, to a blood based system, where most drug testing is performed in blood.  Lasix has no effect on the detection of substances in the blood. ​


  • EIPH has clearly been shown to negatively impact the performance of a horse, a fact that is not hard to understand when we understand that blood in the lungs interferes with the horse's ability to use oxygen. 

  • Numerous scientific studies have shown Lasix to decrease the severity of EIPH.

  • The majority of horses in maximal exertion will experience EIPH at some time or another.

  • It should be no surprise that overall, when studies have looked specifically at the performance of horses racing with Lasix, they performed better with Lasix.

  • The key question is, does Lasix improve performance if there is no EIPH?  Only a few studies have been designed to answer this question.

  • A study using tracheobronchoscopy, found that males and females that did not bleed with or without Lasix had no performance enhancement from the administration of the medication, but geldings (castrated males) did.  However, in that study, horses were raced first without Lasix, in a second race with Lasix, and in a third race without Lasix.  Out of 665 horses initially examined, only 79 exhibited no EIPH over the three races.  Of those, only a group of 18 geldings demonstrated improved performance when Lasix was added.  Curiously in the third race, when the same geldings raced without Lasix, their form did not return to the original no-Lasix race, indicating that the improvement in the second race was unlikely to be related to the Lasix.  Hardly resounding evidence of performance enhancement with Lasix administration.

  • Another study performed on a treadmill used oxygen consumption as a measure of performance.  Because oxygen is used to generate energy, this is commonly equated to performance.  This study found that the Lasix made the horses lose weight, and the oxygen consumption per pound improved...but not the oxygen consumption per horse.  Since races are run by whole horses, and not by the pound, this is further evidence that Lasix does not enhance performance. 

  • Research does not indicate that Lasix improves performance aside from its effect on EIPH.  




In countries where epistaxis, or bleeding from the nose of the horse is the only way EIPH is identified, only 4% of the cases of EIPH are found. Fortunately for the horse, the trainers in these other countries do realize the benefits of using Lasix in the training of their horses, as well as other yet to be proven medications to mitigate EIPH.  Unfortunately, they are not allowed to use Lasix the day of the race – when the horse is going to have to give maximum effort.  Markets for prospective racehorses abroad often claim that their horses are superior because they race free of Lasix and EIPH, but despite this claim, American Thoroughbred bloodlines continue to dominate throughout the world.  Further, many of the most prominent buyers of American horses are people that race outside this country. Not recognizing the proven high incidence of EIPH is one thing, but to also ignore the mounting evidence that, uncontrolled, EIPH can lead to chronic, progressive lung pathology is hypocritical and unacceptable to the trainers, veterinarians and most of the owners in North America. This statement is backed by a Horsemen’s Benevolent Protective Association (HBPA) poll in which over 90% of the owners and trainers were in favor of the use of Lasix on the day of the race.  The North American racing industry is the largest racing industry in the World, by far.  To capitulate to the balance of the world is a little like the tail wagging the dog, especially in light of the mountain of evidence to support the benefits of Lasix to the equine athlete.



According to the 2017 Economic Impact Study of the American Horse Council (AHC), in the United States, over 50 billion dollars is directly attributable to horses and including indirect  effects, the contribution is over 122 billion dollars. Direct employment in the horse industry is almost 500,000 full time jobs, and the indirect impact contributing over 1.7 MILLION JOBS. Green space preservation provided by the horse industry involves 32 million acres of deeded land and 49 million acres of land leased for horse related activities – for a total of 81 MILLION ACRES OF GREEN SPACE PRESERVATION. 

Therefore, despite the average American having minimal interaction with horses, these animals continue to significantly impact the lives of all.  All of those directly involved in the horse racing industry are in awe of these magnificent athletes.  Gambling, entertainment, and the sheer enjoyment of watching the most elite of athletes perform, all while preserving green space,  often in metropolitan areas, where such space is limited.  Horse racing provides all Americans with valuable benefits.



Infant mortality has dropped by 60% in the time since Lasix was first instituted in horse racing.  Life expectancy has increased from 55 to 75.  These improvements in human health are due, in part, to modern medicine and health care.  Advances in veterinary medicine, such as the introduction of the flexible fiberoptic endoscope, have paralleled the advances in human health.  Advocates for severe restrictions on medications for racehorses would have medical decisions for our cherished athletes made, not by the animal's own physician in consultation with the owner and trainer, but by an official in a corner office. This would be absurd and cruel, just as it would be to deprive any animal or human of the benefits that medicine makes possible. Therapeutic medications, those that treat medical conditions of the animals, do not enhance performance, nor do they contribute to the tragic events occurring on the race track.  Therapeutic medications improve the quality of life of the horses, and any arguments to radically restrict such medication simply directs precious resources away from investigation of the true cause of the problems. The medication of racehorses, including that of therapeutic medications, is more rigorously restricted than medications for human athletes, or those entrusted with our safety such as pilots, ship captains, and bus drivers. And yet some unreasonable individuals and organizations attempt to restrict medication even further.  They seem to forget or do not recognize that a racehorse is an athlete.

An example of this “blame the medication” mentality is the recent injuries at Santa Anita Park in California. It is disingenuous and misleading to suggest that the use of race day Lasix was in any way associated with these injuries; in fact, Lasix decreases the likelihood of injury to both the racehorse and the jockey. Santa Anita did not have the increase of injuries before and the trainers, veterinarians, and apparently some other racetrack personnel were the same.  If the weather was a factor, it was more likely related to how the track was maintained during the rainy weather – not the weather itself since Los Alamitos (less than 30 miles away) and Golden Gate, located in the same State and receiving the same rainfall did not experience the increase in injuries.


If a stretch of highway is associated with excessive fatalities, we send out a team of engineers to determine how that road differs from other, safer roads.  Then the road is modified in response to the investigation.  This cannot guarantee that no fatalities will ever occur on that stretch of highway, but it does return the safety to the same level as any other stretch of highway.  The same type of investigation needs to be conducted every time any spike in severe injuries on a race track.  The racing surface, the track base, the cushion, how it is managed in the face of weather all require careful evaluation. Such investigation should include all facets of the industry, horsemen, jockeys, racehorse veterinarians and track managers. One thing is certain – Lasix, in use at every racetrack in California, had no role in these injuries. 


Despite clear evidence in the veterinary scientific literature that Lasix is the only therapeutic medication effective for control of the disease EIPH, some of the stakeholders in the horse racing industry have said that we must abandon the use of Lasix because “the general public cannot tell the difference between Lasix and cocaine.” This is their position even though it will be detrimental to the health and welfare of racehorses. We believe that the general public is smarter than that. Despite the onslaught of misleading and inaccurate information, we believe that the public can be educated, can examine the facts, and understand that this medication is necessary for these magnificent athletes. The proposed ban on the use of Lasix for two-year-old racehorses is especially concerning in light of the mounting evidence that EIPH can lead to chronic, progressive lung pathology if not controlled.

This website was therefore developed to educate the general public and be an advocate for the health and welfare of the horse. Please visit the website periodically for updates on this campaign. 


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