Many years ago, long before veterinary medicine was on my mind, I toured a large equine retirement facility in search of a home for my older mare. When I arrived, the property owner was leading a stiff geriatric gelding slowly out of his stall. She syringed a medication into his mouth, and turned him out in a pasture. At the conclusion of the tour some hours later, I noticed that gelding running freely, bucking and playing with his friends. He was 43 years old, and that medication was Bute.

If your horse has ever had an orthopedic ailment such as degenerative joint disease, you’re probably familiar with the efficacy of non-steroidal anti-inflammatory drugs (NSAIDs). Other common uses for NSAIDs include treating fever, colic, and pneumonia. The following is not an exhaustive list of all NSAIDs but reviews those that are clinically proven or have been otherwise successfully used in horses over the years. In a 2009 survey of 1,400 horse owners and trainers, 96% of respondents used NSAIDs. Even if you are among those who are already comfortable with administrating these medications, your veterinarian should be the guiding professional. 

Mechanism of action

When tissues are damaged or infected, the body produces cyclooxygenase enzymes (COX-1 and COX-2), which are involved in a chemical cascade that creates a group of lipids called prostaglandins. These prostaglandins create pain, inflammation, and fever. What makes NSAIDs so effective for pain relief and healing is they inhibit and interrupt this process. However, because prostaglandins exist in almost all body tissues—and many serve a protective function—there are potential toxicities.

Adverse effects

These can arise from improper or excessive administration, administration without veterinary guidance, or unknown causes. Oral and gastric ulceration, kidney injury, and right dorsal colitis (inflammation in the upper right portion of the large intestine) are well-documented examples. Dehydration or certain pre-existing health conditions can exacerbate adverse effects, so veterinarians are especially judicious with NSAIDs in patients with known compromised health. Administering more than one NSAID at a time can be unsafe, as the redundant mechanisms of action might enhance each drug’s normal activity, increasing the possibility of unwanted effects to the point of causing harm to the horse. Long-term (several months or longer) administration of an NSAID carries additional risks due to its prolonged suppression of protective prostaglandins.

Phenylbutazone (Bute)

Veterinarians generally use Bute to treat a wide range of musculoskeletal conditions. It is a nonselective COX inhibitor (it inhibits both COX enzymes) and comes in oral and intravenous (IV) formulations. A capable individual must administer IV Bute; if inadvertent injection occurs outside the vein, Bute can be very toxic and cause tissue necrosis. Oral Bute is generally cost-effective and just as potent as the IV form. 

Flunixin Meglumine (Banamine)

Banamine is a nonselective COX inhibitor veterinarians often use for pain associated with smooth muscle, including colic and pneumonia, and to treat endotoxemia (bacterial infection in the bloodstream). Along with Bute, Banamine is the mainstay of pre- and postoperative pain relief. Research shows little difference in usefulness between the two for relieving musculoskeletal pain, even though many professionals have pragmatic opinions on why they prefer one over the other for any individual horse. Intramuscular administration of Banamine can result in clostridial myositis, a potentially life-threatening muscle infection, so proper IV administration is also critical. The oral formulation is effective, although its onset of action is longer than that of the IV formulation.

Firocoxib (Equioxx)

This is in a relatively newer class of NSAIDs that’s COX-2 selective, meaning it targets COX-2 enzymes with little effect on COX-1 enzymes, leaving their protective mechanisms intact. Consequently, fewer systemic side effects are associated with prolonged use. For example, in experimental studies Equioxx has resulted in less severe glandular gastric ulceration than Bute. Side effects have still been reported, so seek your veterinarian’s advice when using it for longer than 14 days.

Take-Home Message

These NSAIDs, among others, are very effective for controlling pain, inflammation, and fever associated with many equine conditions. While research and the test of time have consistently shown their value, they are rarely the sole treatment for an illness or injury. Horse owners’ ubiquitous NSAID use for many situations does not diminish the potential risks. It is best to stay with proven products and follow guidance from your veterinarian regarding NSAID choice and dosing regimen.