Horse owners who compete in United States Equestrian Federation (USEF) sanctioned events need to be aware that effective Dec. 1, 2011, horses will not be allowed to compete with more than one of the seven approved non-steroidal anti-inflammatory drugs (NSAIDs) in their systems. The rule was adopted by USEF based on the recommendation of its Equine Drugs and Medications Committee. The first phase of the rule was implemented April 1, 2010, and required a disclosure for horses treated with more than one NSAID, also called "stacking," within five days of a competition.

Hoyt Cheramie, DVM, equine specialist for Merial’s Large Animal Veterinary Services, said the decision to limit NSAID use in competition horses will help owners and trainers avoid some of the inherent risks associated with multiple-NSAID usage.

"No NSAID designed for use in the horse was ever intended to be used in conjunction with another NSAID," he explained. "There are potential side effects of stacking NSAIDs such as diarrhea, loss of appetite, gastric and colonic ulceration, large colon and cecal impaction, kidney damage and right dorsal colitis. Many of these conditions can lead to colic."

In addition to the risks involved with using more than one NSAID concurrently, there are potential dangers when administering even a single NSAID