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Dr. Doug Thal, DVM, Thal Equine

“Hey Doc… my horse has been colicky since last night. I gave him some Banamine and he seemed OK, but now he doesn’t look so good”. This scenario of self-help is very common in my practice. I always ask my clients to call me at the first sign of any colic problem and before they use Banamine®, but there are many horse owners who regularly use two well known but poorly understood prescription drugs without any veterinary guidance. The drugs are “bute” and Banamine®.

Bute (phenylbutazone) and Banamine® (flunixin meglumine) are the most commonly used anti-inflammatory drugs in the horse. They are prescription drugs - they can be bought legally only through prescription by a veterinarian. Despite this, they are everywhere in the horse world. Many who use the drugs do not understand how they work or why they are used. The drugs are highly effective when used correctly but can be very dangerous if misused. While many horses have benefited from the effectiveness of these drugs, many horses have suffered or died as a consequence of inappropriate use.

The purpose of this article is to provide the basic information which every horse owner should know before they administer these drugs to their horses. I will start by defining inflammation, explain why we want to reduce inflammation, and how these drugs do that. I will then discuss some important facts about these two drugs, which every horse owner should know.


Inflammation is a natural and intricate series of biochemical reactions that take place in all animals as a response to injury. The process involves complex reactions between local cells, blood vessels, inflammatory cells and biochemical signals. The first results of inflammation include opening of blood vessels to the area, increased leakiness of blood vessels resulting in swelling, and attraction of infection fighting cells to the site. Products of inflammation include prostaglandins and other inflammatory mediators which help bring about these effects. Some of these mediators directly cause pain. All of these products of inflammation are intended to rid the body of infection or injury, and to prepare it to for healing.

Inflammation is a natural process and it is critical for survival. The problem is that often this process becomes excessive, creating a vicious cycle and causing more tissue damage, pain and suffering than the injury itself. This is where anti-inflammatory drugs come in. Their role is to dampen inflammation by reducing the formation of mediators (prostaglandins), and thus reducing the signs of disease (swelling, pain and fever, for example) while still allowing healing.

Anti-Inflammatory Drugs – “NSAIDS”

Bute (Phenylbutazone) and Banamine® (flunixin meglumine) are two potent anti-inflammatory drugs that are very commonly used in horses. They both belong to a class of drugs known as “NSAIDS” (non-steroidal anti-inflammatory drugs), which includes the familiar drugs aspirin and ibuprofen. Less commonly used equine drugs of this class are ketoprofen, carprofen, naproxen and many others. Because these drugs moderate inflammation, they reduce pain by reducing the formation of certain pain-causing products of inflammation. As anti-inflammatory drugs, though, they do much more than simply control pain. They have great value in treating many problems, from colic to joint injury.

NSAIDS reduce inflammation by blocking prostaglandin synthesis. Prostaglandins come in many types. Some are products of the inflammatory cascade. Others have vital maintenance functions in the body. For example, one type has the role of protecting the stomach and intestinal lining from acid and digestive enzymes. This same prostaglandin has a protective role in the kidney. Unfortunately, NSAIDS not only decrease the production of “bad prostaglandins” of inflammation, they also reduce the formation of these “good prostaglandins” and thus can cause problems to the organs normally protected.

In recent years, new types of NSAIDS have been developed. The goal in the development of the newer generation drugs has been to target the “bad” prostaglandins of inflammation and spare the protective ones. The truth is that much is still not known about these newer drugs and their effects in horses. No drug has yet provided a perfect balance of great effectiveness and excellent safety. Phenylbutazone and flunixin meglumine remain the mainstay of anti-inflammatory therapy in the horse.

Side effects of the use of NSAIDS in horses include:

• NSAIDS as a group can cause intestinal and stomach side effects including gastric and colonic ulcers.
• NSAIDS can cause kidney problems. This is especially true of young horses, but caution must be used in treatment of old horses and those that are otherwise ill or dehydrated.
• NSAIDS are dangerous in foals. Foals are especially sensitive to the intestinal side effects and easily develop ulcers from the use of these medications.
• All NSAIDS have the ability to “mask” a problem, making it look less severe than it really is and give cause for false hope and treatment delays.

For these reasons, it is very important to consult your veterinarian when you use these drugs.

“Bute” - Phenylbutazone

Phenylbutazone (a/k/a butazolidin) is primarily used to relieve musculoskeletal pain and inflammation in the horse. Bute comes in several forms, an injectable liquid for intravenous dosing only, but mostly in oral forms – the familiar paste, tablets and powder. Used correctly, bute is a powerful and effective means of relieving pain and inflammation. Nevertheless, problems can arise due to misuse or overuse:

• Bute is unsafe in all horses at high doses for long periods of time.
• Bute is considered more likely to cause ulcers, especially in the large colon, than Banamine and other NSAIDS.
• Bute is processed, inactivated, and removed from circulation by the liver and kidneys. Young horses have not fully developed their ability to process this drug, and tend to accumulate toxic doses of it. The same concern applies to old horses, or those with underlying illnesses.
• Bute is highly effective, and can mask the signs of mild or moderate lameness. Thus, a horse with a non-displaced fracture on high doses of bute may over-stress the injury, causing worsening of the fracture which may be fatal.
• Bute is somewhat less effective than Banamine® (flunixin) at controlling abdominal pain but can still be useful.
• I almost always dispense oral bute (paste,tablets or powder) to my clients. The injectable solution is for intravenous use only, and must never be given in the muscle. It is severely damaging to tissues if even a small amount gets out of the vein into the surrounding tissues. When this happens, severe swelling develops and the tissue often dies and sloughs out, leaving a huge open wound that can take months to heal.

Banamine® - Flunixin Meglumine

Banamine® is a trade name for the anti-inflammatory drug flunixin meglumine. Banamine® was the only brand of flunixin available for many years. As a result, the name “Banamine” has stuck, despite the fact that the drug is now available from many manufacturers and has different trade names. Examples of these trade names are Flunixamine, Equigesic, etc. Flunixin comes in injectable solution for IV use, a paste formulation, and granules. Although the injectable drug is intended for IV use, many horse owners give flunixin intramuscularly. The drug is somewhat irritating to the tissues when given in the muscle and rarely can cause significant muscle damage and severe bacterial infection.

Banamine® is best known for its use in horses with abdominal pain (colic). No doubt, this drug is a potent pain reliever. It is thought to work on horses with colic by breaking the pain – spasm cycle in the gut. Unfortunately, this drug is also excellent at masking the signs of colic, giving horse owners the false belief that they have “cured the colic,” only to find their horse is critically ill or dead the next day.

The most important concept regarding the use of flunixin ( Banamine®) in the treatment of colic symptoms is to understand that colic is not a disease but is the horse’s way of demonstrating abdominal pain. If the cause of colic pain is simply gas or a spasm, a “shot of Banamine®” may be all it takes to break the cycle and solve the problem. If, however, there is a mechanical problem in the gut such as a feed impaction or displacement, Banamine® will temporarily make the horse look better but to do nothing to fix the underlying problem. The time wasted thinking that the horse has improved can be the difference between life and death. A qualified veterinarian should evaluate any horse with persistent colic signs, in order to diagnose the underlying cause and determine whether other types of medical or surgical treatment is required. A good rule is to always call your veterinarian when you use Banamine® to treat a colic case.

• Flunixin has extra anti-inflammatory benefits which make it especially good for treating intestinal problems (anti-endotoxic effect).
• The same potential side effects discussed for NSAIDS apply to flunixin.


Bute and Banamine® (flunixin) are extremely important drugs in equine medicine. These drugs offer excellent anti-inflammatory and pain relieving effects for horses, but they must be used appropriately. Horse owners should understand the basic concepts of how these drugs work, and their strengths and limitations. In short: when in doubt about the use of these two drugs, do not engage in self-help without first calling your veterinarian.

© Thal Equine, LLC. Reprinted with permission. Visit Dr. Thal at Thal Equine