The Science of Lasix: a View from the "Summit"

There has already been considerable media coverage of this week’s “International Summit on Race Day Medication, EIPH and the Racehorse.” (See, e.g., here,here, and here.) But most of these reports offer the always-tempting us vs. them scenario: “rest of world presses US to eliminate race-day meds.” In fact, the summit was far more informative, and thought-provoking, than that simplistic view suggests. So informative and thought-provoking, in fact, that I will be reporting on it in a series of three blog posts. Today: the science of Lasix and EIPH (“bleeding” in race horses. Next, what the rest of the world actually does. And, finally, some thoughts on how to resolve the conflict between foreign and media pressure to ban all race-days drugs with the economic realities of racing in the US.

(Lots of the presentations at the Summit have been posted online here, so I'll forego the pictures of bloody trachea and scarred lungs.)

I had earlier commented on the Lasix issue, among other drug-related problems in racing, in a piece for the New York Times’ The Rail blog. I’m delighted that attending the “summit” yesterday deepened my understanding of Lasix and its costs and benefits. But, as we’ll see, understanding a problem doesn’t necessarily lead to a solution.

On to the science of Lasix, a topic almost entirely absent from the media reports on the summit.

The first question is how many race horses bleed under the stress of a race or a high-speed breeze? The answer depends on how you define “bleed.” If it means actually bleeding from the nostrils, then the answer is about 1%. If it mains showing even a trace of blood in the trachea when a horse is “scoped” after a race, then the answer is somewhere near 80%, plus or minus 10%. Obviously, the definition that you use determines the scope of the problem and therefore the appropriate solution.

Fortunately, there’s now pretty good evidence to help define the issue better. A recent study of several hundred race horses in South Africa, conducted by researchers from the US, Australia and South Africa and frequently cited at the Summit, used the common veterinary practice of grading bleeding that shows up when a horse is scoped on a scale of 1-4. In the study, 79% of horses showed some signs of blood after racing without Lasix, but so did 57% of those that raced with Lasix. So, while Lasix does reduce both the incidence and the severity of bleeding in a majority of horses, it doesn’t eliminate it. What Lasix does do is to reduce the pressure on the very thin capillaries in the horse’s lung by some 15-20%. And that in turn reduces the “remodeling” of blood vessels and scarring of the lung tissue, making them less likely to bleed next time.

Most horses that “bleed” have a score of 1 or 2 on the 1-4 scale. In the opinion of most of the vets who spoke at yesterday’s meeting, a score of 1 has no impact on a horse’s racing performance, and a score of 2 is more or less on the borderline for performance-affecting. All the vets agreed that severe bleeding (a score of 3 or 4) definitely has an impact on racing performance, as does actual bleeding from the nostril, which is seen in only 1% or so of horses. In the South African study, 20% of horses without Lasix didn’t bleed at all, another 45% bled only to the 1 level, and another25% at the 2 level. In contrast, among horses treated with Lasix pre-race, 43% didn’t bleed at all, 48% bled at the 1 level, and only 9% bled at the 2 level. Thus, some 9% of the horses in the study that did not get Lasix bled at a level that all vets agreed clearly compromised their racing performance, while none of those treated with Lasix bled at that level. Lasix “works,” and in this study at least, it created a level playing field by letting horses that are more likely to bleed perform up to their potential. In that sense, Lasix can be thought of as a performance “enabler” or “optimizer.”

Bleeding also tends to get worse over time, so a horse that starts on Lasix presumably has a lower lifetime incidence of bleeding than one that races without the drug. That effect, though, doesn’t seem to translate into more starts per season or per racing career. Since the introduction of Lasix as a permitted drug in the US, starts per season and starts per career, as reported in the Jockey Club’s Fact Book, have declined by some 25%, to a level that’s on a par with most of the rest of the (non-Lasix) world. One can’t necessarily blame the use of Lasix for the decline in the number of starts, but Lasix apparently hasn’t helped.

Of course, Lasix is also a performance enhancer. Horses treated with Lasix, in the aggregate, perform better than those without the drug. Part of the difference reflects Lasix’s ability to suppress the kind of bleeding that would otherwise interfere with a horse’s performance. And part undoubtedly reflects Lasix’s reduction in a horse’s weight; in the South African study, horses treated with Lasix lost an average of 28 pounds pre-race, while those treated with a placebo lost only 12 pounds. That 16-pound advantage would be considered significant by almost any handicapper. Whatever the mechanism, horses on Lasix do better. That’s why 95% of US race horses run on Lasix, even though, based on the South African study, fewer than 10% of those horses would bleed at a level that substantially interfered with their performance if they raced without the drug.

One thing that Lasix does not do, the vets at the Summit agreed, is mask other drugs that racing authorities test for. Modern testing techniques are very sophisticated, and the only jurisdiction that still believes Lasix interferes with other drug testing is Hong Kong, where Lasix is not permitted at any time, not just when a horse is racing. Hong Kong notwithstanding, the experts at the Summit convinced me that the “masking” argument is no longer valid as a reason for getting rid of race-day Lasix.

One of the most interesting aspects of yesterday’s scientific discussion was the surprising (for me at least) finding that the Flair nasal strip has much the same effect on bleeding as Lasix does. While the Flair’s human equivalent, the Breathe Right strip, appears to have little or no effect on human athletes’ performance, several of the vets in attendance yesterday said that the Flair strip did help in horses. Some trainers used the Flair strip a few years ago, but it seems to have fallen out of fashion and has been banned in some racing jurisdictions, even though its manufacturer is a sponsor of the NTRA’s Safety and Integrity Alliance. If its efficacy is confirmed by additional scientific studies, the Flair strip might be a viable substitute for Lasix.

Tomorrow: how other countries deal with bleeding.