Non-steroidal anti-inflammatory drugs, or NSAIDs, are a type of medication administered to horses for various conditions. Veterinarians typically prescribe NSAIDs for soft tissue and musculoskeletal injuries, as well as for abdominal inflammation and pain. [1]

Specific conditions in horses that are commonly treated with NSAIDs include degenerative joint disease and colic. [2] NSAIDs can also help relieve fever in horses. [3]

Despite the availability of other types of pain medications, NSAIDs remain the most widely used drugs for pain management in horses. They are popular because they are effective, affordable, and easy to administer. [3]

There are currently six FDA-approved NSAIDs for use in horses, but the three most commonly used NSAIDs include phenylbutazone (Bute), flunixin meglumine (Banamine®), and firocoxib (Equioxx®).

It’s important for horse owners and caretakers to familiarize themselves with the differences between these medications in addition to the correct dosing directions and counter-indications. Although NSAIDs are an effective pain management tool, prolonged use can have long-term health effects in horses.

Always consult a veterinarian if your horse’s pain is not improving, especially if you have been administering NSAIDs for longer than the recommended dosing interval on the package label.

How Do NSAIDs Work

NSAIDs are drugs that reduce inflammation, which is the body’s response to tissue damage. They achieve this by inhibiting the activity of cyclo-oxygenase (COX) enzymes, which are involved in promoting an inflammatory response. [1][4]

COX enzymes are required for the production of prostaglandins, chemicals that cause inflammation, pain, and fever in the horse’s body. When NSAIDs block the activity of COX enzymes, the production of prostaglandins is reduced, resulting in less inflammation.

To date, three COX enzymes have been identified: [2]

  • COX-1
  • COX-2
  • COX-3

Of these three enzymes, COX-1 and COX-2 are best understood; less is known about COX-3. [2]

COX-1 & COX-2 Enzymes

Researchers have identified the following characteristics of COX-1 enzymes: [1]

  • Present in nearly all cell types
  • Act as a “housekeeping” enzyme, playing a role in normal physiological functions to maintain homeostasis
  • Required at low levels for normal gastrointestinal function, blood clotting, and renal (kidney) function

As for COX-2 enzymes, researchers have identified the following characteristics: [1][2]

  • Present in most cell types
  • Normally at very low levels in most tissues, but increase during inflammatory responses by up to 20-fold
  • Play a role in maintaining blood flow in compromised kidneys

Enzyme-Selective NSAIDs

Because NSAIDs work by blocking COX enzymes, there are potentially serious side effects associated with their overuse. For this reason, the benefits of NSAIDs should always be carefully weighed against their potential risks, especially with long-term use. [2]

Most negative effects from NSAIDs are associated with inhibition of COX-1 enzymes. This is likely because COX-1 enzymes have a greater importance in supporting baseline physiology than COX-2 enzymes. [1]

For example, COX-1 enzymes are critical for producing prostaglandins that maintain the stomach’s protective mucus lining, preventing gastric ulcers.

In recent decades, researchers have focused on developing NSAIDs that act selectively against COX-2 enzymes as opposed to COX-1. The goal is to preserve the normal housekeeping functions of COX-1 while inhibiting the pro-inflammatory effects associated with COX-2. [1]

Traditional NSAIDs are nonselective, meaning they inhibit both COX-1 and COX-2 enzymes. Prolonged use of nonselective NSAIDs can increase the risk of negative effects on the gastrointestinal tract and kidneys in horses. [2]

Newer COX-2 selective NSAIDs are less likely to have a negative impact on horses’ overall health. [2][5] That being said, horse owners and caretakers should always seek veterinary guidance before administering NSAIDs for longer than the prescribed dosing interval, regardless of which type is in use.

Phenylbutazone (Bute)

Out of all the NSAIDs used for horses, phenylbutazone (Bute) is most commonly prescribed. [1] It is a non-selective cyclo-oxygenase (COX) inhibitor, meaning it inhibits both COX-1 and COX-2 enzymes.

Common Uses

Bute is often prescribed to treat pain and inflammation associated with chronic lameness and navicular syndrome. [1] Horse owners also often use Bute independently to treat a variety of inflammatory and/or painful musculoskeletal conditions.

Although Bute isn’t commonly used for colic, it is sometimes administered prophylact