Bute For Horses, Its Uses, and Its Side Effects

Last Updated on December 26, 2022

Can I borrow some bute for horses? This is a commonly heard phrase both at horse shows and at horse barns, particularly show barns.  Bute is as common in the horse world as flowers are in a garden. 

The bute is basically the equine equivalent to Ibuprofen (Advil, Tylenol, etc.) for people.  Bute can help your horse’s aches and pains, fevers, and sore muscles. But, Bute can also be detrimental if not administered properly.

Overuse of bute can cause serious side effects, and it is just as important to be aware of these side effects as it is to be aware of the drug’s benefits.  In this article, I’ll be discussing what bute is, how it works, what it is effective in curing, and what side effects of overuse can be.

What is Bute for Horses?

The Ontario Ministry of Agriculture, Food, and Rural Affairs define but as the following:

“Phenylbutazone (Bute) is an analgesic (relieves pain) and anti-inflammatory medication, commonly used for the treatment of lameness in horses. It belongs to a group of medications known as non-steroidal anti-inflammatory drugs (NSAIDS). Phenylbutazone is available in many preparations for horses, including 1-gram tablets, oral paste syringes (containing 6 grams or 12 grams/syringe), an injectable (200 mg/ml in 100-ml vials), and oral powder.”

It is a powder or pastes administered to a horse to relieve multiple different categories of pain and discomfort.  But, because of its dangerous side effects, Bute must be prescribed by your vet for you to purchase it; it is not a medicine that can be bought “over the counter.”

Bute can be an extremely helpful tool for increasing a horse’s comfort through times of injury or sickness, but it also has detrimental side effects.  

Because bute is so common in the equine industry today,  is important for horse owners to understand when it is appropriate to use bute, and when bute can become a problem for their horses.

What Is Bute For Horses Used For?

Like Ibuprofen, Bute “blocks” a horse’s pain and brings down any inflammation or swelling.  It also acts to lower a horse’s temperature if a horse has a fever.  Because of these characteristics, Bute is the top pick for treating many different conditions in horses. 

Bute is used to treating muscular discomfort in horses, whether this simply is sore muscles from a hard day of work, or musculoskeletal disorders such as arthritis, laminitis, navicular, or degenerative joint disease.

It is also used to treat infections in flesh injuries that can occur from bites, kicks, unfortunate rolls, or run-ins with the fence or a tree.  Bute acts to not only reduce infection, but also to reduce swelling, and therefore pain in affected areas.  

What is Bute Powder for Horses used for?

How Does Bute for Horses Work?

After Bute has been administered either via syringe or via powder, the majority of the drug remains in a horse’s blood.  Damaged or injured areas of a horse’s body automatically have increased blood flow, as the horse’s body is naturally trying to fix the problem.

Because of this, there are also higher quantities of bute being transported to these areas. Bute blocks chemicals called prostaglandins, which can cause pain.  

While this makes the horse more comfortable, prostaglandins also have important internal functions, which is why it is important to use Bute in low doses, to let the prostaglandins do their jobs. 

The blood eventually flows the bute into a horse’s liver, where it is processed and excreted from the horse’s body within 24 hours of consumption.

In terms of medications, this is a relatively long time for a drug to stay in a horse’s system after administration, and it is a rather long processing time.  This is why it is important not to overuse bute and thereby overwhelm a horse’s liver.

Common Side Effects of Bute

Prostaglandins not only cause pain, but also have an important job of regulating blood flow to a horse’s kidneys, stomach, and gastrointestinal tract.  When these prostaglandins are blocked by the use of bute, they can’t complete these jobs.

Lack of blood flow to the stomach and intestinal tract can increase risk and even cause horses to develop kidney damage or ulcers in their GI tract.  Especially if your horse is prone to either one of these conditions, it is vital to take special care when administering bute to your horse.


For example, my Thoroughbred has been prone to GI ulcers his entire life.  He is on a daily supplement to support GI health, and he gets an ulcer-reducing paste every time his stress levels may increase.  These instances include travel, lack of available turnout, and weather changes.

But, he is also a performance show horse.  After a long day of the show, I want to make sure his muscles and joints stay relaxed and comfortable.  Bute is a perfect way to do this, but I have to be extremely careful with the dosage I use. I also need to consider how many days I choose to use it. If not, he runs the risk of his GI ulcers coming back to full strength.

Can You Overdose a Horse on Bute?

It is possible to overdose a horse on Bute, and this can cause some uncomfortable and long-lasting side effects for horses. There are two different ways in which this can happen – either a one-off dose of Bute which is too high or long-term Bute administration that causes damage to various body systems.

For this reason, Bute should never be given to your horse without the advice of your veterinarian. Even a perfectly healthy horse can succumb to Bute toxicity, although this is more likely to happen in horses that suffer from underlying health conditions.

The issue with Bute toxicity is that the side effects are often long-lasting and may be irreversible. The main problem with Bute is that it restricts blood flow to the gastrointestinal system and kidneys of the horse. This can lead to ulceration of the intestines and reduced kidney function. High doses of Bute can also cause damage to the liver, which will be intensified when additional doses of Bute are administered.

Can Bute make a horse sweat?

Sweating is not a known side effect of giving Bute to horses, but there may be other reasons why a horse would sweat when given Bute. Sweating is a common sign of pain in horses, so you may notice your horse sweating more than normal if it is injured. Some other medical conditions, such as Cushing’s disease, also cause horses to sweat abnormally.

If your horse has been given Bute and starts sweating for no apparent reason, it is a good idea to contact your veterinarian for advice. Your horse may be suffering from an adverse reaction to the Bute, or there may be another undiagnosed medical problem occurring.

Can Bute cause constipation in horses?

The most common and debilitating side effect of Bute administration in horses is a condition called right dorsal colitis. This causes inflammation of the right dorsal colon, part of the large intestine. The colon is responsible for the digestion and absorption of fiber, which makes up the bulk of the horse’s diet.

So, does right dorsal colitis cause constipation in horses? No – the opposite is true! Horses that have right dorsal colitis due to Bute toxicity will not be able to absorb water and nutrients in the large intestine as efficiently, leading to diarrhea. This condition can be very debilitating for the horse and may lead to severe weight loss, dehydration, collapse, and even death.

If your horse is constipated following Bute administration, there may be other reasons for this. For the intestines to work normally, your horse needs a regular intake of fiber and water, and must also move around for the majority of the day. The gentle movement of a horse walking around a paddock helps to propel food through the intestines at a normal rate.

So, if your horse has been given Bute, the chances are that something else may have changed during their daily routine. The horse may be confined to a stable due to lameness or drinking less because of a health problem. Whatever the cause, if your horse’s fecal output does not quickly return to normal, or you notice signs of colic, it is important to seek veterinary advice.

How to Get Bute for Horses?

Bute, or phenylbutazone, for horses is a prescription-only medication. This means that you cannot walk into a store and buy it, but will need veterinary authorization first.

In the vast majority of situations, most veterinarians will need to see a horse for a full clinical examination before prescribing Bute. Don’t be annoyed if your veterinarian refuses to prescribe Bute without seeing your horse – they are doing this to fulfill a legal requirement that is necessary to keep both your horse and the human population safe.

Bute is prescribed by veterinarians at a specific dose – enough to make your horse feel more comfortable, but not so much that this potent painkiller could cause unwanted side effects. This dose is carefully calculated according to the size, age, and weight of your horse, as well as any other health problems and medication they may be receiving. The aim is to keep the dose as low as possible and the course of treatment as short as possible.

Bute must only ever be given to horses that are not intended for human consumption. This medication is extremely dangerous to humans, and traces of it can pass into the human food chain via animal meat products. In many countries, it is necessary to indicate on a horse’s records if it has ever had Bute so that it can never be used for human consumption.

Where can I buy Bute for horses?

Once you have a prescription from your veterinarian, you will have two choices of where to buy the Bute. Your veterinarian will happily supply you with this product, or you can buy it from a pharmacy that supplies animal medication – either online or in person.

For an animal pharmacy, you will need to supply a written prescription from your veterinarian to be able to obtain Bute for your horse. Your veterinarian may charge you for issuing a prescription, but many people find that online pharmacies are cheaper for purchasing larger amounts of Bute. For a shorter course, it is normally more cost-effective to purchase this medication directly from your veterinarian.

How Do I Get My Horse to Eat Powdered Bute?

Horses have very finely tuned tastebuds and will detect even the slightest amount of medication in their feed. Luckily Bute has very little flavor, and most horses will eat feed containing powdered Bute without any problems.

Most people add Bute directly to their horse’s feed. When feeding Bute to a horse, take care to mix the powder carefully with the food. Feed your horse separately away from other horses, and make sure they have time to eat every last part of the food.

Another easy way to feed Bute to horses is to make a Bute sandwich. Take a slice of bread and smear it with something palatable for horses – jam or molasses work well. Sprinkle the dose of Bute onto the filling, and fold the bread in half.

The Bute sandwich can then be fed to your horse by hand. This is a quick and easy way to get Bute into a horse that lives in a herd with other horses, where it may be difficult to feed them separately. Take care to avoid sugary fillings in the Bute sandwich for horses that are overweight or are suffering from health problems such as laminitis, equine metabolic syndrome, or Cushing’s disease.


Bute can be a performance horse owner’s best friend! Bute can be a senior horse owner’s best friend! But it can also be both of these horses’ enemies.  It is an extremely useful tool, but it must be used with caution and with the proper knowledge of its side effects.

Thankfully, Bute can only be obtained by a vet prescription.  Because of this, vets will prescribe an exact dosage for your horse. There is no question as to what is an appropriate amount and what is not; your vet will define this for you and your horse.

I hope this article helped you better understand what bute is, what it does, and what its side effects can be if used improperly.  If so, please share this article, and share with us your experiences (good and bad!) with using bute!


For how long can you safely give bute to a horse?

Bute is a medication given to horses as a painkiller and anti-inflammatory. In the olden days, it was one of the most commonly used medications for horses. Today, it has been replaced by other more effective drugs with fewer side-effects.
In general, you should not give bute to a horse for more than three days unless you have been professionally trained to do so or you are under strict veterinary supervision.
The dosage of bute can be varied, depending on the size of the horse, weight and age. The dosage is usually 0.35-0.5 mg per kilogram of weight for a one-time dose or a daily dose of up to 1 mg/kg body weight per day.

Does bute calm a horse down?

The effects of bute depend on the dosage given, as well as the horse's weight. In general, bute will have a calming effect on a horse because of its muscle relaxant properties.
In general, bute will have a calming effect on a horse because of its muscle relaxant properties. This is why it's the most common drug given to horses who are injured or in pain. Bute can also help control pain and inflammation, as well as reduce the risk of infection.
The calming effect from bute will allow for better rest and sleep which in turn promotes healing from injuries sustained by the horse or from other negative stimuli sources such as environmental stressors or illness.

How quickly does bute work?

Bute can be administered as an oral drench, as a slow-release injectable, or as a drench through the skin of the neck or upper back. Most often is injected into horses as a painkiller and it works very quickly. It can be injected into the horse's muscle or vein. As soon as the injection is given, the horse usually starts showing signs of improvement within minutes and can return to normal within 20-30 minutes after injection.
The effects of bute last for four to six hours after administration, with some effects persisting up to 12 hours after administration. The most common sign that bute is taking the effect is sedation. Sedation is typically seen within 30 minutes after ingestion and lasts about 12 hours.

Can bute cause colic?

The risk of taking bute is that it can cause side effects. The most common side effect that occurs in the intestines is stomach ulcers that can lead to development of colic. This happens because after bute is ingested, it becomes the active ingredient in the animal's stomach lining. So over time, the stomach lining can become irritated or even ulcerated due to constant contact with bute.
The most common symptom of stomac ulcers and colic is abdominal pain. Other symptoms may include nausea, vomiting, loss of appetite, diarrhea, weight loss, fever, and impaired range of motion.
Other possible side effects that can occur with bute are liver damage, kidney damage, and abnormal heart rhythms. The chance of these side effects occurring is reduced if the horse is not given bute for a long periods of time.
So, which horses are more likely to react well with bute? Horses that are generally healthy without any underlying conditions will usually tolerate this drug pretty well.