The most commonly used non-steroidal anti-inflammatory drugs (NSAIDs) in equine medicine are relatively safe, effective, and short-lived at low doses, but their use could mask lameness or other ailments in competing horses, according to international scientists at the recent NSAIDs congress hosted by the Fédération Equestre Internationale (FEI).

Whether NSAIDs should be allowed in competition is a current issue of debate among FEI member organizations–primarily national federations. To assist in this debate, leading pharmacologists, toxicologists, and equine veterinarians presented scientific data on the mechanisms, dosing, and possible effects and consequences of NSAID use to the congress audience in Lausanne, Switzerland, in August.

NSAIDs work primarily by regulating inflammatory mediator enzymes called cyclooxygenases, according to Colin Roberts, BVSc, PhD, FRCVS, veterinary consultant to the Animal Health Trust in Newmarket, England, and member of the FEI medication control panel. The cyclooxygenases can be subdivided into two categories: COX-1, which help maintain normal physiological function, and COX-2, which are more directly responsible for inflammation. "There has been a lot of work in creating NSAIDs that selectively affect the COX-2 enzymes and leave the COX-1 enzymes alone," to minimize adverse effects, Roberts said.

In some horses–particularly young or diseased animals–NSAIDs might negatively affect the kidneys, gastrointestinal system, or liver and could impair the clotting function of the blood, according to Johanna Fink-Gremmels, DVM, PhD, Dipl. ECVPT, professor in the veterinary pharmacology, pharmacy, and toxicology division of the equine clinic at the University of Utrecht, Germany. Although NSAIDs have an "appreciable margin of safety," the risks are increased with long-term use, she said