The Horse

FEB 2018

The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.

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26 THE HORSE February 2018 (Banamine), ketoprofen (Ketofen), and firocoxib (Equioxx). These are classified as non-steroidal anti-inflammatory drugs, or NSAIDs. "Non-steroidal anti-inflammatory drugs are used for their analgesic (pain- eliminating) and anti-inflammatory prop- erties," says Anthony Blikslager, DVM, PhD, Dipl. ACVS, professor of equine surgery and gastroenterology at North Carolina State University, in Raleigh. Adds Lisa Fultz, DVM, Dipl. ACVIM, of Equine Medicine Specialists of South Florida, in Wellington, "NSAIDs are vital in our management of pain and inflam- mation in horses, from literally their eyes … to the tips of their toes." These drugs act by inhibiting the enzyme cyclooxygenase (COX), which has two major forms, or isoenzymes: COX-1 and COX-2. The first isoenzyme, COX-1, plays the role of "housekeeper" by regulating many of the body's processes. Most notably, it acts on the stomach's mu- cosal lining, protecting it by producing prostaglandins to maintain blood flow. (Prostaglandins are natural chemicals in the body responsible for regulating blood flow to many tissues.) The body produces the COX-2 isoenzyme chiefly in response to inflammation. Two classes of NSAIDs are available to target these distinct enzymes: nonselec- tive COX inhibitors and COX-2 inhibitors. Nonselective COX inhibitors do not discriminate; they target both COX-1 and COX-2 and, so, decrease inflammation significantly, but at the cost of inhibiting COX-1's protective mechanisms. These NSAIDs include phenylbutazone, flunixin meglumine, and ketoprofen. Cyclooxygenase-2-selective inhibitors provide similar anti-inflammatory effects by targeting COX-2, but they affect COX- 1 less. Therefore, these NSAIDs carry fewer systemic side effects associated with prolonged use. Equioxx is the only FDA-approved COX-2-selective NSAID for equine medicine. The Side Effects Veterinarians need NSAIDs to manage inflammatory and painful conditions such as colic, pneumonia, and orthopedic pain in horses. However, when used improper- ly, excessively, or without veterinary guid- ance, these drugs can cause unwanted and potentially serious side effects. "It is vital to emphasize that NSAIDs are not vitamins or supplements, and al- though they have a margin of safety, they are medications and have many different effects throughout the body," Fultz says. For this reason, it's important to always involve your veterinarian in decisions to medicate your horse. And knowing the common mistakes and side effects as- sociated with NSAID administration can help prevent your good intentions from becoming dangerous. Improper administration "The risk of giving an NSAID injection improperly can be very disfiguring and painful," Fultz says. "If Bute contacts tissue outside of the vein during attempted IV (intrave- nous) administration, it can cause skin and tissue to slough." This scenario can also cause a blood clot, called a thrombus, in the jugular vein, which impedes blood return from the head to the heart. This results in backflow of blood in the veins of the head and neck, causing these vessels to bulge prominently. "The great thing about the most commonly used NSAIDs is that they all have excellent absorption and efficacy when given orally," Fultz says. "Therefore, the skills and risks associated with injec- tion can … be avoided." Ulceration When administered as oral pastes or ground tablets, NSAIDs occa- sionally cause direct-contact ulcerations on the horse's lips, oral cavity, and/or tongue. But the bigger, more prevalent issue is damage to the stomach lining. Veterinarians recognize that gastric ulceration is a common side effect of NSAID administration. The complex equine stomach has two regions: the squamous mucosa portion and the glandular portion, separated by a distinct line of tissue called the margo plicatus. The glandular portion of the stomach produces the gastric acid and tends to be a little more resistant to it. Remember that NSAIDs inhibit prosta- glandins, which might lead to decreased mucous production and a lower gastric pH. So prolonged NSAID administration can lead to squamous or glandular ulcers, or both. As a result, affected horses might show signs of colic, especially after eating, or go off their feed. If your horse needs to be on NSAIDs long-term, your veterinarian might suggest administering gastropro- tectants simultaneously to prevent gastric ulceration. Right dorsal colitis Ulceration can also occur in the large colon (intestine) during NSAID use, specifically in the right dorsal (upper) portion. This is usually associ- ated with long-term administration of high doses of phenylbutazone; however, it NSAIDs: Help or Harm? COURTESY DR. NATHANIEL WHITE An improperly injected NSAID can cause skin and tissue to slough or a blood clot to form in the jugular. The great thing about the most commonly used NSAIDs is that they all have excellent absorption and efficacy when given orally." DR. LISA FULTZ

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