Scientists are improving equine pain control one NSAID and transdermal patch study at a time

In years past, veterinarians had limited access to analgesics for horses, leaving the animals to suffer from pain associated with colic, laminitis, osteoarthritis (OA), ocular trauma, and myriad other conditions. We now have more options that we once did; however, a void remains to be filled.

“The mainstay of analgesia in horses is non-steroidal anti-inflammatory drugs (NSAIDs), but these are limited in efficacy and can cause gastric ulceration and colitis,” says Rachel Reed, DVM, Dipl. ACVAA, associate professor in Anesthesia Service in the University of Georgia College of Veterinary Medicine’s Department of Large Animal Medicine, in Athens. “Opioids are great but carry their own adverse effects and, more concerningly, the potential for diversion (transferring for illicit use). Most opioids, therefore, cannot be sent home with owners.”

Further, most opioids must be injected in the muscle or in the vein. Options exist for transdermal administration, but those usually cost more, says Reed.

Here we’ll present some of the key studies conducted on medications used for pain control in horses published in the past 12 to 24 months, which centered on NSAIDs and opioid transdermal patches.

NSAID Research in Horses

NSAIDs for Abdominal Pain: No Clear Winner

Citarella et al. (2023) conducted a systematic review to determine if one NSAID could be recommended over another when treating abdominal pain (colic- or castration-related) in horses. They reviewed articles published between 1985 and 2023, searching for studies using meloxicam, flunixin meglumine (Banamine), phenylbutazone (Bute), firocoxib, and ketoprofen. Remarkably, only eight studies met the inclusion criteria during this 38-year period, involving 175 horses with colic pain and 184 horses undergoing castration.

“One reason for conducting this study was that anecdotal observations suggest that the cyclooxygenase-2 (COX-2) selective NSAIDs are not as effective at controlling abdominal pain as the traditional nonselective NSAIDs that block both COX-1 and COX-2,” explains Regula Bettschart-Wolfensberger, Prof. Dr. med. vet., PhD, Dipl. ECVAA. Bettschart-Wolfensberger is head of the section of anesthesiology in University of Zürich Vetsuisse Faculty’s Department of Diagnostics and Clinical Sciences, in Switzerland, and a co-author on the study.

Another reason for performing this study was that phenylbutazone and flunixin meglumine are the two most used NSAIDs for colic in the U.K., U.S., Canada, and South Africa. Scientists believe COX-2-selective NSAIDs (e.g., meloxicam, firocoxib) have a better safety profile than nonselective NSAIDs. Therefore, it would be valuable to know if COX-2 NSAIDs were as effective or more effective as analgesics compared to nonselective NSAIDs. Even understanding if one NSAID offers better pain relief than others, regardless of COX specificity, would be beneficial.

The research team reported this review did not find scientific evidence supporting the widespread selection of flunixin meglumine as the first-line analgesic for abdominal pain. In 80% of the included studies, flunixin meglumine was used, highlighting that flunixin is considered a gold standard, yet without evidence to support this status