You share many things with your horse on a regular basis: long rides, a carrot, and baths (because, let’s face it, no one can stay dry and give a horse a bath!). But medications? According to one research group, a common pain reliever found in many peoples’ medicine cabinets could help relieve pain in horses with laminitis.
At the 2016 American Association of Equine Practitioners’ Convention, held Dec. 3-7 in Orlando, Florida, Jonathan Foreman, DVM, MS, Dipl. ACVIM, presented the results of a study in which he and colleagues tested whether acetaminophen (yes, the same medication that’s in your trusty Tylenol bottle) effectively relieved foot pain in horses. Foreman is a professor of veterinary clinical medicine at the University of Illinois College of Veterinary Medicine Veterinary Teaching Hospital, in Urbana.
Veterinarians often prescribe traditionally used non-steroidal anti-inflammatory drugs (NSAIDs)—such as phenylbutazone (PBZ) or flunixin meglumine (FM, Banamine)—to help reduce or eliminate foot pain (such as that associated with laminitis). But such drugs carry potentially dangerous side effects, including toxicity, ulcer development, and renal (kidney) disease. Alternatives to classic NSAIDs include narcotics and topical treatments, but neither is without complications or challenges. As such, researchers are still on the hunt for effective treatments with fewer side effects.
Foreman and colleagues recently compared acetaminophen’s efficacy in relieving foot pain to that of FM. Foreman said the drug is well-absorbed in horses’ small intestines and is metabolized in the liver.
“Acetaminophen overdosing is one of the most common causes of liver failure in humans,” he explained. “So, it’s critical to know if the drug causes liver disease in the patient receiving it.”
The researchers induced reversible lameness in eight healthy adult horses by using an adjustable heart bar shoe that could be tightened with a screw to elicit lameness ranging from mild to severe. After lameness induction, the team administered 1.1 mg/kg of FM orally, 20 mg.kg of acetaminophen orally, or left horses untreated to serve as controls. Each horse received each treatment with a week between trials.
Foreman said control horses had higher heart rates (a previously proven pain indicator) and lameness scores (the higher the score, the less sound the horse) than horses that received FM or acetaminophen. However, there were no significant differences between heart rates or lameness scores in FM- or acetaminophen-treated horses, he said.
The team also monitored horses’ liver enzymes following administration and found no evidence of elevation, suggesting there was no liver damage from the 20 mg/kg acetaminophen dose, Foreman said.
“It was concluded that acetaminophen at this oral dosage was comparable to FM and both were more efficacious” than the control treatment, he said.
Foreman noted that, while this is the first oral acetaminophen trial conducted in horses, veterinarians in the U.K. administered acetaminophen to a horse with laminitis in all four feet and coffin bone rotation in three. He said the practitioners had treated the horse with PBZ, lidocaine, and morphine with diminishing success. After receiving acetaminophen with a dose of PBZ, however, the horse’s demeanor improved, he began moving and eating better, and he stood more squarely. The team confirmed the drug’s effects after taking the horse off acetaminophen, observing his condition deteriorate, and then readministering the drug with the same positive results.
There’s still no data regarding acetaminophen’s pharmacodynamics or toxicity in horses, so further research is warranted. However, Foreman encouraged practitioners to consider this medication for laminitic horses.
“I wouldn’t put down another lamintis horse without suggesting this to the client as an alternative to try,” he said.