As a vet, I thought I would put forth my two cents- sorry for the length.
Lasix is a loop diuretic which means is acts specifically on a part of the kidney to cause not only fluid loss but significant losses of potassium, calcium and chloride. Horses on the program must be managed accordingly, otherwise, they can develop conditions such as atrial fibrillation (flipped heart), thumps and/or tying up to name a few.
Having said that though, the Lasix program was originally developed to protect the health of the horse. Research studies involving treadmill tests as well as track workouts have demonstrated that Lasix does reduce the severity of bleeding (EIPH) likely through a decrease in pulmonary arterial pressure amongst other things. However, when looking at horses racing on Lasix (primarily thoroughbreds) the numbers that bleed still seem to remain the same, however, in general, performances improve. This begs the question, does Lasix improve performance through improving the severity of bleeding or through other mechanisms such as weight loss (which has recently been demonstrated), as a calming agent or as a masking agent etc.? If there was only one cause of bleeding, there would only be one medication to treat it – however, there are many causes including airway inflammation (allergies, post-viral inflammation), atrial fibrillation (or other cardiac arrhythmias), functional upper airway problems (ie displaced soft palates) , and lameness particularly sore front feet/legs in trotters. The reason speculated for the latter is that, trotters that are lame in the front feet/leg shift more of their weight to the hind end. Because they have a diagonal gait, they compress the abdominal organs against the back part of the diaphragm and lungs, where bleeding from the lung begins (this is at the level of the 17th rib – almost to the flank area). And yes, it is likely that most horses bleed, but then most if not all horses that are athletes also bleed to some degree (ie barrel racers, jumpers ,draft horses that pull). If one was to do a lung wash on every horse after it races blood would be present in the fluid (and we don't know how this impacts performance). But because we only check them with endoscopy we only see blood in horses that have bled significantly for the blood to have traveled from the level of the 17th rib to the windpipe. There is a lot of controversy in the veterinary world concerning the use of Lasix for EIPH – hopefully a better choice can be found but it won’t likely occur anytime soon. Other “bleeder” shots out there are also diuretics and can cause some of the same side effects as Lasix. As for the horse that started this conversation, “Perfect Host” aka “Spanky” is a fat and shiny, beautiful black stud horse, who is utterly spoiled by Walter. He’s been on the Lasix program on and off since 2002 and looks no worse the wear for it. He would make a great riding horse, when retired, and I would not be concerned about the status of his lungs (only about the presence of his testicles!)

Bottom line is that there are drugs for bleeders that are far easier on a horse and less damaging than lasix. Besides, lasix is a diuretic which we all know can be used to mask other drugs which raises the question, why is it being used.

Greg Parke

Shayne Barrington

Horses bleed naturally?? That means "all" horses bleed?? And there is a "normal" amount of bleeding?? All we need to do to combat bleeding is to leave them outside longer when they are young?? And you say lasix horses will be worth nothing when they retire??? I'm glad your not a spokesperson for OSAS!!! Mrs. Magee you also go on to say that lasix does "sludge up" the blood not allowing the oxygen in the blood to get to the brain,legs etc. These statements are what I find incredible!!! Dr. Llewellyn could you please explain to this lady(and the rest of this websites readers) the real purpose and effects of the lasix program so we can all get a veterinarian's point of view instead of some one's opinion.

Thank you
Shayne

I'm in agreement with Mr. Jackson. Ban Lasix. Horses bleed naturally with the exertion levels that they go through during racing. If the extent of that bleeding excedes "normal", why the heck are they still racing? The lungs of a horse that bleeds beyond normal are probably shot to heck, likely caused by spending far too much time indoors as young horses and breathing in dusty air. Can you imagine what these horses are going to be like when they are retired from racing? Likely good for nothing and in a terrible state due to breathing problems.
The use of Lasix is far too common. I can't for the life of me understand why a drug such as this, diuretic in nature, is allowed in any sport. High performance horses require more hydration not less. Just think about how the blood travels more quickly through the horses' systems taking oxygen to the brain, lungs, legs, etc. as required due to the extreme amount of work being done. Now sludge it up and what are those very important organs and body systems getting in the way of fresh blood carrying much needed oxygen? It blows my mind that we have allowed this to go on this long. Incredible!

how about banning all lasix

I am a fan of this sport.
I've read the abbreviated transcript of the recent ORC judgements on Whelan and MacDonald.
They read more like an Abbott and Costello routine, than a legal proceeding affecting the lives of real people and the integrity of our sport.

I am not questioning the hearings or judgements themselves, simply the manner in which they were conducted , heard and rendered.

A much higher level of professionalism is in order.

Walter Whelan is a friend and client of mine and showed me the horse Perfect Host, that received the positive Lasix test.On approaching the horse he flexed and twisted his neck, which apparently is an idiosyncrasy of his. To administer an intravenous injection to this horse is difficult because of this habit. An alternate explanation for the positive test is that some of the Lasix was injected perivascularly {outside the vein}.This would affect the test result owing to a different rate of absorption. The horse had received Lasix many times without problem, so I doubt that his metabolism is different from that of other horses and the actual problem is inadvertent perivascular injection.To prevent any suspicion of prior treatment of this horse or of a metabolic anomaly,I would suggest a blood sample be taken prior to the administration of Lasix. Should the horse be called in for testing and the Lasix level is higher than it should be, the pre race sample could then be analysed.This would remove the fear of a positive test from the unwitting trainer or confirm prior administration.
I understand the significant cost of testing but this situation is rare and a simple pre race blood sample would clarify the situation.