Bizolin Gel, Butatron TM Oral Gel, Phen-Buta-Vet Inj., Phen-Buta-Vet Tabs, Phenyl Gel-4, Phenylbutazone Inj. Phenylbutazone Inj. 20%, Phenylbutazone Tabs, Phenylzone Paste, Pro-Bute TM Inj., Pro-ButeTM Tabs

Phenylbutazone is a non-steroidal anti-inflammatory drug. It also has analgesic (pain relief) and antipyretic (fever-reducing) activity. The drug acts directly on tissues and its most marked effects are on inflamed tissues.

Phenylbutazone is indicated for the treatment of a wide range of musculoskeletal disorders, including muscular sprain and strain, muscular overuse (including both muscular damage and strain/damage of the tendons attaching muscles to bone), tendonitis, acute joint injury/strain/sprain, and arthritic conditions.

Anti-inflammatory drugs do not cure musculoskeletal problems. They do control the inflammation, thereby helping to decrease the ultimate damage and scarring, and making the horse more comfortable during the painful periods.

Pain and inflammation control also serve to make movement more comfortable. This helps prevent any permanent decrease in range of motion of the affected areas so that they do not become too “scarred down.” Pain control/exercise must be carefully counterbalanced with the veterinarian’s instructions to limit stress and avoid reinjury or worsening injury to damaged areas.

Phenylbutazone also is often used to help control pain from injuries, infections, laminitis, or virtually any other source of pain. Its effectiveness under these conditions will vary widely, depending both on the individual horse and the cause of the pain. It is a reasonable first choice drug for pain control.

Phenylbutazone also is often used to control the fever associated with viral or bacterial infections. Its use under these circumstances may mask the severity of the problem and/or any worsening of symptoms. It should only be used when the veterinarian has determined that symptoms are severe enough to prevent normal eating/drinking, and/or that they are otherwise interfering with the horse’s recovery.

Appropriate antibiotic treatment must also be continued.

Phenylbutazone may be given orally or by the intravenous route. Oral preparations available include tablets (to be crushed and mixed with feed or given with a balling gun), paste, and gel forms.

The maximum manufacturer’s recommended intravenous dose is 1-2 grams/1000 Ib daily. The upper dose limit is recommended for initial injection to achieve rapid control of the inflammatory process. This should then be decreased.

The maximum manufacturer’s recommended oral dose is 2-4 grams/1000 Ib daily. Because blood levels drop rapidly, it is suggested that the total daily dose be divided and the drug be administered every 8 hours for best effect. Many veterinarians and owners get satisfactory results giving phenylbutazone only once or twice a day.

Extreme care must be used when phenylbutazone is injected intravenously. Phenylbutazone is extremely irritating to tissues and can cause extensive swelling, pain, tissue damage, and even loss of tissues if injected outside the vein. Repeated injections of phenylbutazone into the same vein may also cause damage or destruction of the vein itself, possibly leading to chronic local swelling and edema of the areas of the body normally drained by the vein that has been damaged.

When giving phenylbutazone orally, follow instructions for proper administration of gel or paste forms. The mouth should be inspected to be sure that it is free of any grain or hay, rinsing if necessary. The medication should be injected on the back of the tongue with the head held slightly elevated. Hold the head in this position or keep the horse on short cross-ties for several minutes after administration of paste or gel. This prevents it from falling out of the horse’s mouth, and keeps the horse from spitting it out. Water buckets also should be removed for approximately 15 minutes after administration to prevent the horse from rinsing part or the entire dose out in the water.

When using crushed tablets in feed, the full dose must be consumed to be effective. Most horses will readily accept the drug when mixed in with sweet feed.

For horses that will not take the medicated grain, try mixing the medication in a small amount of molasses and adding this mixture to the grain. If this does not work, a thick mixture can be made of phenylbutazone and molasses, or phenylbutazone and an antacid such as Milk of Magnesia, which is then placed directly onto the back of the horse’s tongue.

Overdoses with phenylbutazone can occur relatively easily. Once a blood level of phenylbutazone reaches a toxic level the metabolism of phenylbutazone is inhibited and elimination of the drug is reduced. Overdoses result in mouth and tongue lesions, gastrointestinal ulcers, and possibly hemorrhage. This is particularly a risk with young and stressed horses, or horses ill from other causes.

Damage to the lining of the gastrointestinal tract can be severe enough to cause the horse to leak significant amounts of protein from his blood into the intestine. The lowered blood protein levels result in edema, usually in the legs and along the belly. General symptoms include thirst, decreased appetite, weight loss and weakness that is, in part, secondary to the low protein and low levels of calcium in the blood. Advanced cases progress to renal (kidney) failure and death (see below). Damage to the kidneys also has been associated with prolonged use of phenylbutazone, particularly at high dosages.

Extended use of phenylbutazone also may cause damage to the portal vein in the liver, or other liver abnormalities. Phenylbutazone should not be used in horses known to have preexisting liver, kidney), or gastrointestinal disease.

Studies in other species show that phenylbutazone is highly bound (attached to) to the proteins in the serum blood, that also serve to carry other drugs. Therefore, concurrent use of other drugs that are normally highly bound to serum proteins may result in greater action and/or toxicity of those other drugs.

Phenylbutazone also increases the anticoagulant effect blood thinning of the drug Coumadin. It should therefore be used with great caution, if at all, in horses receiving Coumadin therapy for conditions such as laminitis or navicular disease.

NSAID toxicities are additive, and NSAIDs should not be used in combination.

Studies in other animal species have shown that phenylbutazone is potentially toxic to the embryo and can appear in umbilical cord blood and in the milk. Caution is therefore advised in using phenylbutazone in pregnant or nursing mares.

Detection Time Information: Phenylbutazone’s pharmacological effects are not thought of as lasting longer than about 24 hours after a clinical dose, particularly an IV dose. Phenylbutazone or its metabolites may be detected in plasma and particularly in urine for longer periods (up to 7 days or longer) after administration of a course of phenylbutazone therapy. The ARCI-recommended plasma level threshold or tolerance level for phenylbutazone is 5 mcg/ml in blood. The Canadian authorities report a 4-day detection time for this drug in horses, while Australian work reports a 5-day detection time.

Horseman’s Comments and Conclusion to this article at the bottom of this page.


Human Version
(More likely, you had no idea that this is a human drug; how many people do you know that take it? Read below why they don’t)

Brand Name Butazolidin

(Also available in generic form)

Type of Drug Anti-inflammatory agent.

From “The Pill Book”

Prescribed for

Local inflammation of bone joints that cannot be controlled by Aspirin or other anti-inflammatory drugs. Some examples are gout, rheumatoid arthritis, osteoarthritis, and bursitis.

General Information

This drug should never be taken without strict medical supervision. Phenylbutazone should be used only for the short term relief of pain due to inflammation of muscles, tendons, and joint area. It has anti-inflammatory, analgesic, and fever reducing properties. This drug is quite useful but is limited by its side effects and adverse drug reactions (*)

Phenylbutazone and its sister drug Oxyphenbutazone are toxic and dangerous and should be used only when absolutely necessary (1). The list of potential side effects is long. Therefore, any change in habits or unusual effect which may be even remotely connected with the use of these drugs should be reported immediately to your doctor.

Cautions and Warnings

You should not take Phenylbutazone if you have a history of symptoms associated with gastrointestinal inflammation or ulcer, including severe, recurrent, or persistent upset stomach(2). This drug is not a simple pain reliever and should never be taken casually (3). It should not be prescribed before a careful and detailed history, plus physical and laboratory tests, have been completed by the doctor. Always discuss your state of health and medical history with your doctor completely before taking this medicine. If your problem can be treated by a less toxic drug such as Aspirin, use that first and try to avoid taking Phenylbutazone. Never take more than the recommended dosage: This would lead to toxic effects(4). If you have blurred vision, fever, rash, sore throat, sores in the mouth, upset stomach or pain in the stomach, feeling of weakness, bloody, black, or tarry stool, water retention, or a significant or sudden weight gain, report this to the doctor immediately. In addition, stop taking the drug. If the drug is not effective after1 week, stop taking it.

Pregnancy /Breast-feeding (5)

This drug crosses into the blood circulation of a developing baby. It is not recommended for use late in pregnancy because of the possibility that the drug will affect your developing baby’s heart. It may delay or prolong your labor. Studies in laboratory animals have shown that this medication produces birth defects. Pregnant women, or those who might become pregnant while taking this drug, should not take it without their doctors’ approval. When the drug is considered essential by your doctor, the potential risk of taking the medicine must be carefully weighed against the benefit it might produce.

This drug passes into breast milk and should not be taken if you are nursing an infant. The drug can cause severe blood problems in a nursing infant. Use an alternative feeding method if you must take this medicine.


Seniors are more likely to develop the blood, stomach, kidney, and liver side effects of this drug because of a general reduction in kidney function. People 60 years of age and older should be limited to short periods of treatment (no more than 1 week, if possible) because of the possibility of severe, possibly fatal, reactions. Some doctors recommend that drug dosage be reduced by half in people age 60 and older.

Possible Side Effects

The most common side effects are stomach upset, drowsiness(6), water retention.

Less common side effects include gastric or duodenal ulcer, ulceration or perforation of the large bowel, bleeding from the stomach, anemia, stomach pain, vomiting, vomiting of blood, nausea, diarrhea, changes in the components of the blood, water retention, disruption of normal chemical balance of the body (8). This drug can cause fatal or nonfatal hepatitis, black-and-blue marks on the skin, serum sickness, drug allergy serious enough to cause shock, itching, serious rashes, fever, and signs of arthritis. It has been known to cause kidney effects including bleeding and kidney stones. Phenylbutazone may be a cause of heart disease, high blood pressure, blurred vision, bleeding in the back of the eye, detachment of a retina, hearing loss, high blood sugar, thyroid disease, agitation, confusion, or lethargy.

Drug Interactions

Phenylbutazone increases the effects of anticoagulant (blood thinning) drugs, Phenytoin, Insulin, and oral antidiabetic agents. If you are taking any of these drugs, discuss this matter with your doctor immediately.

Food Interactions

Avoid alcoholic beverages. Phenylbutazone causes stomach upset in many patients; take your dose with food or antacĀ­ids, and if stomach pain continues, notify your doctor.

Usual Dose

Adult and child (age 14 or over): 300 to 600 milligrams per day in 3 to 4 equal doses for 7 days. If dose is effective it can then be reduced to 100 to 400 milligrams per day, depending on the condition being treated.

Senior: to be given for 7 days because of high risk of severe reactions. Not to be given to senile patients.

Child (under age 14): not recommended.


If symptoms of nausea, vomiting, convulsions, euphoria, depression, headache, hallucinations, giddiness, dizziness, coma, rapid breathing rate, continued stomach pain, and insomnia or sleeplessness appear, contact your doctor immediately.

Special Information

This drug can make you drowsy and/or tired: Be careful when driving or operating equipment.(7)

If you take Phenylbutazone once or twice a day and forget to take a dose, take it as soon as you remember. If it is almost time for your next regularly scheduled dose, skip the one you forgot and continue with your regular schedule. Do not take a double dose.

If you take it 3 to 4 times a day and forget to take a dose, and you remember within about an hour of your regular time, take it right away. If you do not remember until later, skip the forgotten dose and go back to your regular schedule. Do not take a double dose.

Horseman’s Comments

This part should be taken very seriously and one should observe the horse closely as his level of performance may be reduced. (Back to 1)

It is a known fact, that this drug is very abusive to the digestive system, mainly to the stomach itself. (Back to 2)

There are other alternative drugs for reduction of fever. One of my favorites was “Dipyrone”. Dipyrone may be difficult to obtain but here is a link where you can find it. Vet prescription required. Link here> (Back to 3)

Many people often believe “The More The Better”. I have seen people on the track and farms give horses more than 20cc in one dose. I believe that if this drug doesn’t work in maximum of two pills or 10cc per day, than it will not work at all, no matter how much one will give the horse. (Back to 4)

One should take note of this part as I have seen often many pregnant or nursing mares on high doses of this drug. (Back To 5)

This would concern me, especially when using on a Jumper. I am sure that there are many folks who would say that they had no problems with it. However, not all animals react to the drug the same way and there may have been situations where the horse was blamed for his reduced performance due to this drug. (Back To 6)

If you are not supposed to drive, what about the horse jumping where he really needs a great deal of the eye and body coordination? In my experiences I have noticed in few cases that the horses were more nervous before their performance that was thus greatly effected. One should keep in mind that some horses will not do well when on this drug. (Back To 7)

This should be of concern to racing folks. (Back To 8)

Noticed effects

I have noticed on several occasions a negative effect on the horse’s performance. In some cases I’ve seen increases of nervousness in horses, mainly prior to a race.


I am not suggesting in anyway, (Back*) that this drug should not be used in horses. The purpose of this article is to prevent the abuse of this drug and often it’s unnecessary usage. I have used it many times in cases of founder or very small daily dosage when the horses suffered from pain, like navicular disease, other lameness and as an anti-inflammatory agent etc. I’ve tried to avoid this drug, if possible, in the presence of infections. Using it in combination with antibiotics, especially in the viral infections had never worked well for me. The result was often a relapse and much worse than the original. I believe that this drug will limit the horse’s ability to fight the infection. Dipyrone with the antibiotics worked for me much better, since we often need to use fever reducing agent in such cases. I will not use Butazolidin in case of an infected abscess in the hoof. I have been a witness of too much prolonged and unnecessary suffering of horses when treated with Butazolidin in such cases.

I believe that Ibuprofen (Advil etc) is more effective pain killer than Butazolidin, though the effect lasts only about 4 hours, while the Butazolidin works noticeably well into a 16 hours range. I also believe that Ibuprofen is less abusive to the system then Butazolidin.

Butazolidin is to be used only by the consent of a veterinarian and according to his instructions. If prescribed, you may want to ask him for alternative medications if possible.