To Salix or Not to Salix

In the wake of the PETA videos, which portrayed our majestic sport in a most unflattering light, we are left reeling from the backlash.  While most of what was shown in the video was either legal (the use of Salix and thyroxine) or just edited to the extreme (video of the state veterinarian drawing a post-race blood sample for drug testing, while the commentary implied that something illicit was taking place), certainly there were things that were offensive (the non-stop stream of profane language) and things that were clearly illegal, such as forging documents for illegal workers.  The unfortunate ramifications from this video seem to be taking the form of a rallying cry against raceday medication, which, of course, means no Salix.  The clip of the track vet telling the PETA girl that Salix is performance enhancing because of the weight loss is damning.  He failed to explain the repercussions to the animal of bleeding in the lungs, how scar tissue builds up over time, impairing the horse’s long term respiratory health…or perhaps he did explain it and it just didn’t make the video.  However, if Salix is performance enhancing, oughtn’t it be banned?

  Not so fast.  The scientific paper that first suggested performance enhancement by Salix was published in 1990¹.  It showed only that geldings raced faster on furosemide with no statistically significant difference among fillies and colts.  (Meaning that any performance enhancement is negligible.)  Geldings also race longer than fillies and colts, and hence are more likely to have the effects of chronic bleeding. A previous study² showed improved performance associated with Salix, but this study was performed with known “bleeders”  so the obvious conclusion is that is that any difference in performance is exactly the difference between how well the horse would have raced had it not bled, irrespective of the furosemide (ie Salix is performance enabling).  In fact, a well designed study in 1996³ looking at horses in treadmill exercise tests showed no difference whatsoever between a horse’s exercise performance with Salix and without Salix.

 The same 1996 study mentioned above is oft quoted in the vernacular of the anti-Salix contingent, as supportive of their position.  However, the truth lies in the actual details of the study.  When calculated on a weight for weight basis, the horses had higher oxygen consumption (meaning they performed more efficiently), however, the actual oxygen consumption was unchanged.  Which is exactly what we would expect if Salix had no effect on performance, despite the change in weight.  The vet caught so ominously on video saying they run faster because they are lighter should be embarrassed, not for saying what he obviously believed, but for not carefully reading the very paper he was quoting.

What about the case for the use of Salix?  Certainly racing occurs all over the world without it, which is the primary driving argument for the naysayers.  So let’s again go to the scientific literature and investigate the facts.  A series of studies^4-11 published in 1987 carefully investigated the clinical, diagnostic and necropsy findings of a group of 26 horses retired from racing in Hong Kong.  This group of horses were almost all known bleeders.  The findings were of severe, permanent pulmonary damage.  Clearly, horses are not immune from bleeding in Hong Kong, and more importantly, bleeding was proven unequivocally to cause permanent and severe pulmonary pathology. So, what is to be done?  We look again to the published scientific literature.  The ultimate placebo controlled, cross-over study on the efficacy of furosemide was finally performed by Hinchcliff et al, in 2009¹², funded by the Jockey Club.  As a scientist who has designed and performed many studies, this was the Holy Grail of all study designs, a rare opportunity in Veterinary Science.  This paper showed beyond a shadow of a doubt that furosemide ameliorates in all and prevents in some, EIPH.  In this study, NO horses bled a grade 3 or 4 on furosemide, which answers the question of:  is this the right thing to do or not.  Clearly, yes.

 So, the scientific literature concludes that racing on Salix is beneficial to the health and welfare of the individual horse, and Salix is just as likely (or more likely) to enable normalized performance rather than enhance performance.   The states obviously came to an agreement a long time ago that, just in case it IS performance enhancing (an infinitesimally small effect, if there), we should identify horses that race on furosemide with an L in the program, in order to provide transparency to the public.  This is an effective model, and, according to the Jockey Club’s own sponsored research, should remain.  We should not aspire to the model of foreign lands, many of which have restrictive medication rules for the purpose of human food safety.  Rather than base our reactions on arguments, such as “everyone else does it,” we should rely on the facts and science to guide our future.  Should we react to the PETA video?  Yes.  Should our reaction be to eliminate raceday medication?  I think not.

 

 

1.     Sweeney CR, Soma LR, Maxson AD, Thompson JE, Holcombe SJ, Spencer PA. Effects of furosemide on the racing times of Thoroughbreds. Am J Vet Res. 1990 May;51(5):772-8.

2.     Soma LR, Laster L, Oppenlander F, Barr-Alderfer V.  Effects of furosemide on the racing times of horses with exercise-induced pulmonary hemorrhage.  Am J Vet Res. 1985 Apr;46(4):763-8.

3.     Hinchcliff KW, McKeever KH, Muir WW, Sams RA. Furosemide reduces accumulated oxygen deficit in horses during brief intense exertion. J Appl Physiol (1985). 1996 Oct;81(4):1550-4.

4.     O'Callaghan MW, Pascoe JR, Tyler WS, Mason DK. Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. I. Clinical profile of horses. Equine Vet J. 1987 Sep;19(5):384-8.

5.     O'Callaghan MW, Pascoe JR, Tyler WS, Mason DK. Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. II. Gross lung pathology. Equine Vet J. 1987 Sep;19(5):389-93.

6.     O'Callaghan MW, Pascoe JR, Tyler WS, Mason DK. Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. III. Subgross findings in lungs subjected to latex perfusions of the bronchial and pulmonary arteries. Equine Vet J. 1987 Sep;19(5):394-404.

7.     O'Callaghan MW, Pascoe JR, Tyler WS, Mason DK. Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. IV. Changes in the bronchial circulation demonstrated by C.T. scanning and microradiography. Equine Vet J. 1987 Sep;19(5):405-10.

8.     O'Callaghan MW, Pascoe JR, Tyler WS, Mason DK. Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. V. Microscopic observations.  Equine Vet J. 1987 Sep;19(5):411-8.

9.     O'Callaghan MW, Pascoe JR, O'Brien TR, Hornof WJ, Mason DK. Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. VI. Radiological/pathological correlations.  Equine Vet J. 1987 Sep;19(5):419-22.

10.  O'Callaghan MW, Hornof WJ, Fisher PE, Pascoe JR. Exercise-induced pulmonary haemorrhage in the horses: results of a detailed clinical, post mortem and imaging study. VII. Ventilation/perfusion scintigraphy in horses with EIPH.  Equine Vet J. 1987 Sep;19(5):423-7.

11.  O'Callaghan MW1, Pascoe JR, Tyler WS, Mason DK. Exercise-induced pulmonary haemorrhage in the horse: results of a detailed clinical, post mortem and imaging study. VIII. Conclusions and implications.  Equine Vet J. 1987 Sep;19(5):428-34.

12.  Hinchcliff KW, Morley PS, Guthrie AJ. Efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses.  J Am Vet Med Assoc. 2009 Jul 1;235(1):76-82.