“Older NSAIDs such as ketoprofen and phenylbutazone decrease inflammation by inhibiting enzymes involved in inflammation, including one called cyclooxygenase or COX,” explained Laura Petroski-Rose, a veterinarian for Kentucky Equine Research.
Blocking this enzyme decreases inflammation, though COX actually has some redeeming qualities. For example, COX plays a protective role in the health of the lining of the gastrointestinal tract. This is why inhibiting COX with NSAIDs can cause ulcers in the stomach and even intestinal tract, particularly the right dorsal colon.
“Years of research revealed that several forms of COX exist. COX-2 appears to play a larger role in inflammation, whereas COX-1 protects gastrointestinal health,” Petroski-Rose said. Because of this, researchers developed NSAIDs that block COX-2 specifically, leaving COX-1 to do its job of protecting the horse from ulcers. Examples of COX-2 selective NSAIDs include firocoxib and meloxicam.
Sounds like a fairytale ending to solve an important health issue in horses, right?
Not quite.
As brought to light in a recent study*, some COX-2 NSAIDs still cause gastrointestinal damage, even in healthy horses. In the study, both phenylbutazone and firocoxib resulted in gastric ulceration. Specifically, treated horses had similar degrees of ulceration to the squamous portion of the stomach, but firocoxib-treated horses had less severe ulceration of the glandular portion. Further, firocoxib resulted in less inflammation of the intestine than phenylbutazone.
Based on these results, additional research regarding NSAID selectivity and usage is needed, especially considering how frequently this class of medication is used in equine practices. The researchers said, “In addition, studies examining different dosing protocols of these and other NSAIDs are warranted to optimize safety and efficacy of such treatment.”
To help horses requiring NSAID administration, Petroski-Rose said, “Protect your horse's gastrointestinal tract during any stressful period, be it illness, injury, or travel, not just during times of NSAID administration. Consider a research-proven product designed to support gastrointestinal health.”
*Richardson, L.M., C.M. Whitfield-Cargile, N.D. Cohen, A.M. Chamoun-Emanuelli, and H.J. Dockery. 2018. Effect of selective versus nonselective cyclooxygenase inhibitors on gastric ulceration scores and intestinal inflammation in horses. Veterinary Surgery 47(6):784-791.
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