Many equine caretakers have given or received these suggestions time and time again: "Just give him some Bute," or "a little Banamine should do the trick." While the use of these medications—both non-steroidal anti-inflammatory drugs, or NSAIDs—are indicated in some cases, it's not uncommon for the substances to be overused. At the 2012 Western Veterinary Conference, held Feb. 19-23 in Las Vegas, Nev., one veterinarian discussed when NSAID use is indicated and what can go wrong if the drugs are overused.
As Elizabeth G. Davis, DVM, PhD, Dipl. ACVIM, associate professor and equine section head at the Kansas State University College of Veterinary Medicine, explained, NSAIDs have become "extremely commonplace" in the horse industry. This class of medication is known for its anti-inflammatory and analgesic properties, she said, and is often used clinically to "improve patient status and minimize pain."
Some of the most popular systemic NSAIDs veterinarians and horse owners use are phenylbutazone (PZB or Bute), flunixin meglumine (Banamine), and firocoxib (Equioxx). Also gaining popularity is diclofenac sodium (Surpass), which is a topical NSAID. Other less commonly used but still effective NSAIDs are ketoprofen (Ketofen) and etodolac (Etogesic), Davis added.
Indicators for use include, but aren't limited to, pain management for injuries or illnesses, pain management for chronic disease (such as osteoarthritis or laminitis); and fever control.
How Do They Work?
"The mechanism of action for NSAIDs is important to understand, particularly when we consider the use of several of these agents concurrently (also known as stacking) and recognize that many of the agents target the same enzyme system," Davis explained.
Essentially, NSAIDs impair the inflammatory process by inhibiting the enzyme cyclooxygenase (COX). Cyclooxygenase converts arachidonic acid—derived from the membranes that surround cells—into molecules called prostaglandins. Prostaglandins participate in generating inflammation and fever. They are involved with the muscle soreness and stiffness that develop after an overstrenuous workout; the swelling and tissue deformation associated with injuries like bowed tendons; and fever in a horse with influenza. In horses with degenerative joint disease, prostaglandins contribute to the chronic inflammatory responses of joint effusion (fluid escape) and pain that result in a shortened stride or limp.
"What we've learned in the past two decades is that there are several forms of COX (1, 2, and 3) and some medications target one enzyme preferentially," Davis explained.
The majority of commonly used NSAIDs are general COX inhibitors, while some newer NSAIDs specifically inhibit COX-2, she added. The most common COX-2 inhibitor on the market today is firocoxib.
What Can Go Wrong?
Even when NSAIDs are used appropriately, the drugs can still prove damaging to the patient, Davis said, and not all horses handle NSAIDs in the same manner. While many horses have no problems when an appropriate dose of medication is administered on a semi-regular to regular basis, other animals can develop complications even when they consume lesser amounts of the substances. It's not clear why some horses handle medications so differently than others.
But researchers and veterinarians do know what kind of damage NSAIDs can inflict upon the horse. Davis explained that because NSAIDs compromise the body's normal protective mechanisms, it leaves the horse at risk for developing a number of complications including:
- Protein loss;
- Ulcers (gastric and oral);
- Right dorsal colitis; and
- Renal papillary necrosis.
Davis noted that dehydration, some preexisting conditions (such as ulcers), and high dose or chronic NSAID administration can increase the likelihood of developing complications.
NSAID toxicity can have a guarded prognosis, Davis noted, so caution should always be used when administering drugs to horses. If toxicity is suspected veterinary consultation is essential. Therapeutic strategies typically include:
- Discontinuing NSAID use (despite the fact this might not seem like a problem, Davis noted that for horses that depend on low-dose NSAIDs to remain comfortable—like those with osteoarthritis or chronic laminitis—this step can be a challenge. In these cases, she recommends finding another means of pain control for the animal, such as a veterinarian-prescribed opioid drug.);
- Treating for concurrent gastric ulcers;
- Employing frequent, small volume feedings of a low-residue feed (such as roughage or complete pelleted feeds); and
- Monitoring hematologic values (such as protein levels).
With treatment, she explained, the horse's attitude and appetite should improve, and blood work should show increased protein levels and normalized kidney values.
If one NSAID works well, two should work even better, right? Wrong. Davis discussed numerous studies indicating that using more than one NSAID concurrently puts the horse at greater risk of developing complications or toxicity. Stick to administering one NSAID at a time, she suggested.
Additionally, if administering two different NSAIDs concurrently is a bad idea, Davis stressed that administering an NSAID and a steroid at the same time is worse. Steroids like dexamethasone are much more potent than NSAIDs, she explained, and should not be used in conjunction with one another.
Even though a dose of Bute or Banamine might not seem like a big deal, NSAIDs should always be used with extreme caution. Work with a veterinarian to determine if a particular horse could be at risk of developing NSAID-related complications. If NSAID toxicity is suspected, seek veterinary assistance immediately to improve the horse's chance of survival.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.