Antihistamines and NSAIDs and nutraceuticals, oh my! Have a question about equine drugs or medications at Equestrian Canada (EC) sanctioned competitions? EC’s Equine Medication Control Committee is here to answer your questions on the EC Equine Medication Control program.

What is stacking?

Stacking is a common term used to describe the use of two allowable non-steroidal anti-inflammatory drugs (NSAIDs) in a horse’s system at the same time. Both may be within allowable limits, yet the fact that two are present simultaneously is deemed as a positive test.

Times of increased risk to potentially stack could occur when a change between NSAIDs is made, or if a horse accidentally receives the wrong medication at feed time. Previcox has a comparatively long withdrawal time, and is typically one of the two NSAIDs involved in a stacking positive. The potential for this unique positive test illustrates the need to be vigilant about all medications, even those that are allowable and are being administered at appropriate times and dosages.

Please consult the EC General Regulations, Article A1003 Permitted Medications, and your EC Medication Control Guide, as withdrawal times vary widely between medications.

Do you have a question you’d like the Equine Medication Control Committee to answer? Send your inquiries about the EC Equine Medication Control program to

Please note, this does not constitute legal advice. Information included in this article is for informational purposes only. It is not, and should not be taken as, advice regarding a particular situation. You should not rely on, nor take or fail to take any action based upon this information. You are encouraged to seek legal advice regarding your circumstances, and you should not rely upon anything you have read in this article without seeking appropriate legal advice regarding the application of EC Equine Medication Control Rules to your particular circumstances.

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