Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are some of the most commonly used equine medications. They come in several forms, including tablets, powder, paste, or as an injectable.
As their name implies, NSAIDs help to control inflammation in the body. Therefore, they are used for a variety of equine ailments such as pain caused by muscle, ligament, or tendon injuries, osteoarthritis, wounds, and colic.
The most commonly administered NSAIDs for horses include:
- Phenylbutazone (Bute)
- Flunixin meglumine (Banamine)
- Diclofenac sodium (Surpass)
- Ketoprofen (Ketofen)
- Firocoxib (Equioxx, Previcox)
NSAIDs can improve your horse’s comfort level and exercise tolerance when dealing with injuries or other problems. While NSAIDs do have their place in equine veterinary care, it is important that they are used correctly to minimize the risk of adverse effects.
NSAIDs can cause side effects, even when given at the recommended dosage rates. Adverse reactions can affect gut health, nutrient absorption, immune function and your horse’s overall well-being.
Horses are most at risk from negative side effects when NSAIDs are given for too many consecutive days, are overdosed, are given in combination with other NSAIDs (“stacking”), or are administered with certain other medications.
Every horse may tolerate NSAIDs differently. Consult with your veterinarian to learn about the proper use of NSAIDs to minimize the risk of side effects.
NSAIDS for Horses
NSAIDs have anti-inflammatory and analgesic (pain-relieving) effects when administered to horses. NSAIDs work by blocking an enzyme known as cyclooxygenase (COX).
This enzyme is used by the horse’s body to make immune compounds called prostaglandins, which are produced at the specific area of tissue damage or infection.
Prostaglandins are hormones that are involved in healing processes such as inflammation, blood flow, and also blood clotting.
When cyclooxygenase is blocked, this leads to a reduction in these processes. As a result, NSAIDs can relieve discomfort caused by fever and reduce inflammation and the pain associated with it.
COX-1 versus COX-2 Selective NSAIDs
There are two main classes of NSAIDs: those that block COX-1 enzymes and those that block COX-2 enzymes. 
COX-1 and COX-2 enzymes both produce prostaglandins that promote inflammation, pain, and fever, but only COX-1 enzymes produce prostaglandins that activate blood platelets and protect the stomach and intestinal wall.
Traditional NSAIDs such as Bute and Banamine are COX-1 selective. Because of this, they can lead to damage in the gastrointestinal tract (especially the lining). That is why horses on Bute and Banamine are are susceptible to gastric ulcers and other issues with digestive function. 
They can also have other side effects. In rare cases they can affect kidney function and cause bleeding disorders.
Are COX-2 NSAIDs Safer?
Some of the newer NSAIDs were developed to block COX-2 instead of COX-1 enzymes in an attempt to lessen the negative effects on the horse’s gastrointestinal system.
This includes the widely used Equioxx and Previcox (Firocoxib), which is often recommended for horses with osteoarthritis.
However, COX-2 selective NSAIDs, including Equioxx, may not be completely safe in every circumstance either.
Studies in people indicate that COX-2 selective NSAIDs have led to decreased incidence of damage to the stomach, but they have been less effective in reducing NSAID-related injury in the small and large intestine. 
The most common side effects associated with NSAID use in horses involve the lining of the gastrointestinal system (mucosa) and the kidneys. These effects may be worse in ill horses or those with current gastrointestinal injury. 
NSAID Impact on the Horse’s Foregut
As already noted, the most common side effect of NSAIDs in horses involves harm to the gastrointestinal tract. This can include the stomach and the small intestine, collectively known as the foregut.
Since NSAIDs inhibit prostaglandin production, which is important for repairing damaged gastrointestinal mucosa, this can lead to delayed mucosal repair.
In fact, studies have shown that horses with small intestinal ischemic injury (which involves a lack of oxygen delivery to the tissue) that are given NSAIDs can have a “leaky” gut for up to 18 hours after administration. 
Leaky gut is associated with the following adverse symptoms in horses:
- Increased risk of colic
- Impaired immune function
- Risk of ulceration
- Reduced nutrient absorption
When the gastrointestinal barrier is not functioning properly, it can increase the risk of pathogens and toxins entering the horse’s body. It can also interfere with the normal uptake of nutrients from the diet which could lead to secondary nutrient deficiencies.
Horses with ulcers can be fed Visceral+ which is designed to support gastric and hindgut health and support immune function.