Lasix sheds water out of the body. This is why the discussion has been had about allowing horses to gulp water after a race instead of having small drinks when permitted. They are essentially running dehydrated.
In humans it reduces fluid in the body for diseases like heart disease and kidney problems.
Its been a long standing controversy in racing for years now. Used to prevent horses from bleeding in excessive exercise. Lasix is banned in the majority of countries except the US as a race-day medication. In 2014 a country-wide Lasix ban was supported by Todd Pletcher, Kieran McLaughlin, and Richard Mandella as well as officials involved with Breeders Cup. Mclaughlin was once a staunch supporter of Lasix but took the time and energy into doing his own research in his own barn to see if Lasix was actually needed and his results were surprising.
Officials representing horsemen groups have been saying for years now that “the majority of horses bleed and Lasix is the safest drug to keep them from bleeding.” Rick Violette is one of those trainers in support of it
Horses given Lasix on race day pass 10-15 liters of urine between the point the drug is given and the point in which the horse is taken to the track and are not permitted to drink during that time. Horses pass this amount of Urine as an average daily amount. Due to this excessive urinating, by post-time they can be as much as 10-20lbs lighter. This is why Lasix can be viewed as a performance enhancing drug in a race.
The other issue is the concern that Lasix can mask other performance enhancing drugs. When a horse is under extreme diuretics; the amount of fluid they pass is so great that it has been proven that it can mask other drugs the horse may have been given If the horse was to undergo a urine test at that point. this is why the 250mg dosage came about; to prevent the masking of other drugs. But since that came about, the approve dosage has been increased to 500mg.
Veterinarians have long cautioned that they do not see any evidence that Lasix causes greater risk of disease but they have cautioned the long term side effects that can arise from regular, long term use of Lasix.
There is also the argument that Lasix is weakening the breed, and perhaps it is. When Lasix came about; the average number of starts per horse per year was around 12. Since then, it has decreased to about 6/year. There is science studies that show that EIPH is an inherited trait. And when we mask bleeding in racehorses in the US; we never see how severe it may be in some horses and because the level in which it affects the horse is never noted, the horse goes to the breeding shed with little care or interest in it.
There is no scientific evidence that states horses are in pain because of bleeding, there isn’t enough nerves in that area of the lungs to initiate a response and veterinarians have stated that when a horse bleeds from the nostril at a low level, they notice the fluid there like humans would notice mucous in their airway. Its more of a nuisance.
I am in full support of using Lasix on known severe bleeders who need it. I am not in support of broadly using it across the board as an end-all with no investigation or knowledge into whether or not the horse being administered it even has a bleeding problem that’s severe enough to warrant using it. Here in American we use it on just about every horse that starts which I think is very much the wrong thing to do.
