Over the last few years, we have seen sporadic cases of horses reacting to drugs being administered that were intended for use in other species. This has included severe (potentially life) threatening myositis reactions resulting from administration of injectable vitamin and mineral supplementations, (B12 and selenium injection), skin reactions from off label use of cattle pour-ons and abscesses developing on the neck from contaminated medication that had been stored incorrectly in a dairy shed. There have also been incidences of animals showing a ‘positive swab’ at competition following administration of supplements to horses that were licensed for other species. The detection of prohibitive substances in racehorses and competition horses is becoming tighter with low to no threshold in the minimum detection level, and it is likely that further tightening of these rules will be seen in the future.

Medications and supplements have to undertake large numbers of clinical trials in order to prove their efficacy, their safety and appropriate clearance times for use in the species that they are licensed for - if it isn’t licensed for a horse – then it is unlikely that these trials would have been taken out. Multiple supplements and nutraceuticals are on the market now and while most are batch tested to prove their ingredients are what has been stated on the label, a few are not. To ensure that your horse is clear of supplements, medications and topical treatments with no previous stated competition withhold, a clearance time of 36 hours (‘One clear day rule’) has been recommended by Harness Racing New Zealand and New Zealand Thoroughbred Racing and should be applied. For farms that have current Restricted Veterinary Medicines (RVM)s for other species (e.g. Dairy Herd, Sheep etc) these RVMs are for those species identified only, and repeated use of these medications on horses on the farm without Veterinary consultation will run the risk of these RVM privileges being taken away.

If you have any further concerns regarding the use of medications in horses or questions about competition withholding times, please contact us at VetSouth Equine.