You can’t read very much about horse racing without hearing about the drugs that are used. The most common of these seems to be Lasix. What is Lasix? The name of this drug is furosemide and the scientific name is 4-chloro-N-furfuryl-5-sulfamoylanthranilic acid. It’s also known as Salix. In human medicine, it is used as a diuretic. It draws water out of the body, and given to people who retain fluids and develop edema, which is an accumulation of tissue fluid often in the lower legs or lungs. So it is a drug commonly used in human medicine to combat the symptoms of liver or heart failure.
But for horses, specifically, race horses and sometimes eventers, barrel horses, polo ponies, draft pull horses and endurance horses, Lasix, if its use is legal in the sport, may be given not for treating symptoms of a disease, but as a preventative. Horses that work very hard may suffer from something called Exercise-Induced Pulmonary Hemorrhage or EIPH. The severity of bleeding is graded one to four. A horse that is obviously bleeding is graded as a four. These horses will appear to have a nosebleed after they run, a condition called epistaxis.
The blood isn’t just from broken blood vessels in the nose, however. Increased blood pressure as a horse gallops or pulls hard causes the blood vessels in its respiratory tract to explode. This can happen with little evidence that it is occurring and it can take an examination by a veterinarian to detect. Some horses will very obviously be ‘bleeders’. It’s thought that up to 85% of racehorses will bleed at some point in their race career.
But whether the bleeding is obvious or not, it affects the performance of the horse and can have both short and long-term effects. Blood can fill the airways in the lungs decreasing the normal function - similar to a person trying to run with congested lungs. And, over time, the breakdown of the tiny blood vessels can cause the walls of the vessels to weaken and scarring to occur in the lungs. Severe bleeding can end a horse’s performance career. But even slight bleeding may affect a horse’s ability to do strenuous work. And very occasionally, a severe bleeder may die.
That’s where furosemide or Lasix comes in. When the drug is given to a horse, it causes the horse to shed fluids. A horse given Lasix will urinate enough to lose a slight amount of weight. This reduces the amount of plasma in the blood. The plasma is made up of about 90% water and it is the carrier of all the other stuff in the blood. By reducing the volume of plasma in the bloodstream, the blood vessels are less likely to rupture when they are under the stress of exertion. This helps in both the short and long term.
Not all sports allow the use of Lasix, and the use of Lasix for racehorses on race day is not allowed in most places outside North America. Its use is controversial, even though horses that are put on Lasix perform much better than without. And, there is controversy over when the drug should be administered. In the U.S. Lasix can be given up to four hours before a race. There seems to be some argument to support this race day use. A study by a team of researchers from the University of California showed that “93% of the horses given Lasix four hours before a race had grade 0 bleeding”, while only 63% of those given Lasix 24 hours before a race had grade 0 bleeding.
And there is some speculation that it isn’t the drug’s ability to decrease bleeding that improves a horse’s performance. Some feel that the water weight loss is responsible for the horse's faster speed. There is a very unpopular opinion that is used only to mask other performance-enhancing drugs. And that means it has no place in horse racing or any other competition at all.
Lasix is banned in New Zealand and Australia. Racehorses that bleed (at least, galloping racehorses, not sure about harness rules) are banned from racing for three months. And if they bleed a second time they must be retired and never race again.
I've heard of a few promising horses sold to the US so they can continue racing on lasix.
Bleeding isn't always EIPH-related. We've got a couple broodmares who bleed from stress or heat. On a hot summer's day they'll have blood pouring from one or both nostrils and be happy as larry otherwise. Some racehorses probably suffer something similar, or otherwise bang their nose and rupture the delicate tissues.
Lasix is banned in New Zealand and Australia. Racehorses that bleed (at least, galloping racehorses, not sure about harness rules) are banned from racing for three months. And if they bleed a second time they must be retired and never race again.
I've heard of a few promising horses sold to the US so they can continue racing on lasix.
Bleeding isn't always EIPH-related. We've got a couple broodmares who bleed from stress or heat. On a hot summer's day they'll have blood pouring from one or both nostrils and be happy as larry otherwise. Some racehorses probably suffer something similar, or otherwise bang their nose and rupture the delicate tissues.
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