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. [6]

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. [7]

They can also have other side effects. In rare cases they can affect kidney function and cause bleeding disorders.

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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. [1]

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. [2][8]

NSAIDs such as Bute and Banamine block COX-1 enzymes and can negatively impact gut health by damaging the intestinal lining. COX-2 selective NSAIDs such as Firocoxib are less damaging but can still cause adverse effects.

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. [2]

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.

Excessive NSAID use is a major risk factor for ulcers. Horses that have been diagnosed with gastric ulcers should not be given any type of NSAID as it will further exacerbate the problem.

Horses with ulcers can be fed Visceral+ which is designed to support gastric and hindgut health and support immune function.

Prolonged NSAID use can increase risk of gastric ulcers and cause leaky gut, which can trigger immune responses and impair nutrient absorption.


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Impact on the Horse’s Hindgut

The most common and serious side effect of long-term NSAID usage with horses is known as right dorsal colitis (RDC).

The condition is also referred to as hindgut or colonic ulcers, and it usually involves the administration of Bute.

Though many horses develop RDC when owners administer Bute incorrectly, some horses may develop the condition even on recommended doses of Bute.

According to one study, RDC and hindgut dysfunction may affect as many as 60% of horses. In serious cases, the condition has a high fatality rate. [3]

Horses affected by RDC may experience:

  • Decreased performance
  • A rough hair coat
  • Reduced appetite
  • Recurring colic or diarrhea
  • Weight loss

RDC is characterized by damage to the intestinal mucosa, which is the inner lining of the intestinal tract. When the permeability of the mucous barrier is increased, it can result in water leaking from the body into the bowels, causing loose stools or diarrhea.

It can also result in protein-losing enterocolopathy, where protein in blood leaks into the bowels. This is why your veterinarian may want to check your horse’s blood protein levels to ensure they are not too low.

Diagnosing RDC, however, can be difficult since a gastroscope (used to diagnose gastric ulcers) will not reach the horse’s colon. Instead, veterinarians will typically make a presumptive diagnosis based on bloodwork and observation of symptoms.

Treatment for RDC includes immediate discontinuation of all NSAIDs and a low residue diet. Often it also requires administration of the drug, Misoprostol, which is a synthetic prostaglandin which helps stimulate tissue healing in the gastrointestinal tract. [2]

Dietary changes should be considered in horses affected by hindgut ulcers. You can submit your horse’s diet for analysis and our nutritionists can provide complementary advice on what to feed your horse.

A common side effect of excessive NSAID use is hindgut ulcers, which can lead to recurrent colic, weight loss, and rough coat.

NSAID Effects on the Gut Microbiome

Evidence also suggests that NSAID use can lead to an imbalance in the gut microbiome in both people and animals.

One study showed that when administered to adult horses for 10 days, both COX-1 and COX-2 selective NSAIDs significantly altered fecal microbial populations. [1]

The gut microbiome plays an important role in immunity and overall health for horses. A disruption or imbalance in these “good bacteria” can lead to an increased risk of illness or infection.

If you suspect your horse’s gut microbiome has been altered due to NSAID use, consider adding a probiotic or digestive health supplement to help restore balance and hindgut function.

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NSAID Effects on the Kidneys

NSAIDs can also inhibit prostaglandins that are produced in the horse’s kidneys. This, in turn, affects blood flow, oxygen delivery, and filtration in these vital organs.

NSAID-induced injury may lead to the death of kidney tissue, referred to scientifically as renal necrosis.

Horses that are volume depleted, meaning they have a deficit in extracellular fluid volume due to loss of total body sodium, are most at risk for this side effect. [2]

One sign of kidney damage from NSAIDs is urinating more frequently than normal. Banamine, Ketofen, and Bute have all been implicated in causing kidney damage in horses.

Keeping your horse hydrated and feeding salt or an electrolyte formula can help to support kidney function and reduce the risk of colic.

NSAID Effects on Blood Clotting

In healthy people and animals, prostaglandins maintain a balance between blood clotting and hemorrhage, but NSAIDs can disrupt this process. Several studies in humans have shown that COX-2 selective NSAIDs can have cardiovascular side effects, including increased risk of heart attack and stroke.

Though this same risk has not been documented in horses, a related side effect is catheter-associated jugular thrombophlebitis (blood clot blocking the jugular vein when a catheter has been inserted).

This issue appears to be more of a factor in critically ill horses, especially those with endotoxemia related to gastrointestinal disease. [2]

The Dangers of Stacking NSAIDs

Stacking” is the practice of administering more than one NSAID at a time to achieve a greater pain-relieving effect for the horse.

Once somewhat common on racetracks, this practice is now recognized as dangerous and has since been ruled a violation of the U.S. Equestrian Federation medication rules.

Whether it’s a combination of COX-1 selective NSAIDs, COX-2 selective NSAIDs, or both, the risks of stacking outweigh any possible benefits for the horse.

In one study in which horses were given Bute and Equioxx paste by mouth for 10 days, significant changes in serum creatine and total protein were observed. The researchers concluded that giving these two NSAIDs together may result in kidney disease. [4]

Administering more than one NSAID at the same time may also alter the way both drugs interact within your horse’s system. Stacking may enhance or slow the metabolism of one or both drugs.

Stacking NSAIDs to increase pain relief in your horse is particularly problematic and should be avoided. Drug interactions can increase the risk of serious side effects.


NSAIDs with Omeprazole for Ulcers

Another caution to heed: While technically not considered “stacking”, NSAIDs should not be given in conjunction with the drug Omeprazole.

Researchers have noted that combined Bute and Omeprazole administration led to increased intestinal complications in horses. [5]

If your horse is currently on any type of medication, always check with your veterinarian before giving them an NSAID.

Dangers of Using NSAIDs with Foals

Little research is available on the effects of using NSAIDs with foals, but it appears that young horses are especially prone to developing harmful side effects from NSAIDs.

In one study, researchers administered 1.1 mg/kg of Banamine either orally or intravenously to foals. This led to the development of gastric ulcers in many instances. It also led to oral ulcers in some foals. [3]

Because of these study findings and the overall lack of information regarding NSAID use with foals, horse owners should not use any type of NSAID unless under the care of a veterinarian.

Instead, seek veterinary advice with any foal that is ill or injured and consider natural alternatives for pain relief.

Incorrect Administration of Injectable NSAIDs

It’s best to leave the administration of intravenous forms of NSAIDs (or any intravenous medication) to a veterinarian, as there a number of risks that come with incorrect administration.

For instance, many horse owners keep injectable Banamine on hand, but muscle damage and/or serious infection can occur if it is given in the muscle instead of the vein.

Bacterial infection associated with incorrect Banamine administration usually starts as warm swelling under the skin 6-72 hours after the injection has been given.

Bacterial toxins are released into the bloodstream and horses quickly become very ill. They often show the following signs:

  • Depression
  • Colic
  • Purple gums
  • Reluctant to move

If this happens to your horse, seek immediate veterinary treatment, as this condition can be deadly.

NSAID Side Effects in Critically Ill Horses

Critically ill horses appear to be the most susceptible to negative side effects from NSAIDs. Banamine use is especially controversial in horses that have recently undergone colic surgery because it slows the recovery of injured mucosa in the small intestine. [2]

Horses with endotoxemia are also at higher risk of gastrointestinal injury from the administration of Banamine and other NSAIDs.

Unfortunately, there are no effective alternatives to NSAIDs for these horses. [3]

Clinical Signs of NSAID Toxicosis

Horses can develop NSAID toxicosis from a one-time overdose of NSAIDs or from receiving doses of (usually COX-1 selective) NSAIDs over an extended period of time. These horses may display the following symptoms:

  • Difficulty eating due to oral ulcers
  • Hypersalivation
  • Pain when swallowing due to esophageal ulceration
  • Excessive recumbency
  • Anorexia (loss of appetite)
  • Lethargy

Horses that have developed gastric ulcers due to overuse of NSAIDs may lay down after eating, show signs of colic, or may refuse to eat.

Horses with hindgut ulcers may have soft manure, diarrhea, or swelling along the midline of the belly.

These symptoms may occur days or even weeks after NSAID administration.

Safe Use of NSAIDs

Though no NSAID comes without the possible risk of adverse side effects, there is still a place for them in veterinary medicine. Short-term use at appropriate dosages is unlikely to cause long-lasting side effects.

Using these types of medications as directed by your veterinarian will reduce the odds of negative side effects.

Because horses usually show few outward signs of initial adverse effects from NSAIDs, owners may not realize the dangers they pose. A horse may not show symptoms until significant damage to the gastrointestinal tract or kidneys is present.

Because of this, veterinarians and researchers recommend that horse owners use as low a dose as possible for as short a time as possible. [2]

Horse owners can also use natural alternatives to support joint health and reduce discomfort from certain injuries.

Examples of alternative supplements to consider include MSM, hyaluronic acid, and Omega-3 fatty acid supplements.

If your horse is currently using NSAIDs, it is recommended to take extra steps to support their digestive health and protect against the development of ulcers.

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