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Phenylbutazone, often known as bute, is a crystalline substance having the structure shown at right.
- Structural name: 4-butyl-1,2-diphenyl-3,5-pyrazolidinedione
- Chemical formula: C19H20N2O2
Oxyphenbutazone, the major metabolite of phenylbutazone, differs only in the para location of one of its phenyl groups, where a hydrogen atom is replaced by a hydroxyl group (making it 4-butyl-1-(4-hydroxyphenyl)-2-phenyl-3,5-pyrazolidinedione).
Phenylbutazone is used as a non-steroidal anti-inflammatory drug (NSAID) for the treatment of chronic pain, including the symptoms of arthritis. Its use is limited by its side-effect of suppressing the production of white blood cells by bone marrow and sometimes causing aplastic anemia.
The International Agency for Research on Cancer (IARC) places it in Group 3, i.e., "not classifiable as to its carcinogenicity to humans".
Benzone is also used as a class name for the active ingredients in sunscreen that end in "benzone" (such as oxybenzone, dioxybenzone, avobenzone, and sulisobenzone), which are chemically unrelated benzophenone derivatives. These chemicals offer protection against UVB.
Uses of phenylbutazone in horses
Phenylbutazone is a common NSAID used in horses, mainly for treating pain and to lessen fevers. Applied to horses, the main uses for bute include:
- Musculoskeletal disorders: sprains, muscle pain from overuse, tendonitis, joint pain and injuries, and arthritis, as well as to provide pain relief from injuries or infections, as well as laminitis, and to control fevers. Bute does not work well on colic pain. It works directly on inflamed tissue.
- Analgesic: Pain relief from injuries or infections, as well as laminitis
- Antipyretic (fever reducing)
Bute does not work well on colic pain.
Phenylbutazone controls the inflammation of musculoskeletal problems, which reduces the ultimate damage of the problem and alleviates the pain. Control of the pain also allows the horse free range of motion. However, bute will not cure any musculoskeletal problems.
If bute is used to control a fever, it may mask other symptom. Therefore, bute should not be used for that purpose unless a veterinarian has concluded that the horse would not be able to eat or drink without its use, or the fever might hinder the horse's recovery.
Dosage and administration
Bute may be given orally (paste, powder, feed-in) or intravenously. It should not be given intramuscularly or injected in any place other than a vein, as bute can cause tissue damage. Tissue damage may also occur if the drug is always injected into the same vein.The maximum oral dose recommended by manufacturers is 2 to 4 g/1000 lb (4 to 9 mg/kg) per day. Manufacturers recommend that the dose be divided equally and given every 8 hours for maximum results, although most horse owners give it every 12-24 hours for convenience, usually giving 1-2 grams in the morning and at night.
Intravenously, the maximum daily dose recommended by manufacturers is 1 to 2 g/1000 lb (2 to 4.5 mg/kg). The maximum dose is usually given when treatment with Bute is first begun, and then dosage is decreased. It is important to remember that bute may cause severe tissue damage or loss of tissue if injected outside a vein. The vein itself may be damaged if it is repeatedly used as an injection site. Edema may also occur in the tissues supplied by the vein, should the vein be damaged.
Bute should never be given in high doses. Always follow a veterinarian's advice on the administration of the drug.
Side effects and disadvantages of phenylbutazone
Bute, like many NSAIDs, can cause gastrointestinal ulcers and kidney damage if overdosed or used for a prolonged time. Bute may also cause lesions on the horse's mouth and tongue, as well as hemorrhages. This is especially true with young, ill, or stressed horses.Bute may cause severe damage to the lining of the gastrointestinal tract, possibly causing the horse to leak considerable amounts of protein from his blood into his intestine. This may cause edema of the legs and belly. Symptoms of leakage include: decreased appetite, thirst, weight loss, weakness, and if progressed, kidney failure and death.
Do not use Bute in combination with blood thinners or with other NSAIDs (all NSAIDs are additive), or in horses with known kidney or liver problems. When used with other blood thinners (such as Coumadin), such as in horses with laminitis or navicular disease, Phenylbutazone amplifies the anticoagulant effect.
Phenylbutazone should be used cautiously in pregnant or nursing mares, as it may be toxic to the embryo and can be transferred via the umbilical cord and by milk.
High doses of Phenylbutazone may be considered a violation of rules under some equestrian organizations. Bute may remain in the blood stream 4-5 days after received.
History of phenylbutazone in racing
In the 1968 Kentucky Derby Dancer's Image, the winner of the race, was disqualified after traces of bute were discovered in a post race urinalysis. Owned by prominent Massachusetts business man Peter Fuller and jockeyed by Bobby Ussery, Dancer's Image remains the only horse in history to win the Kentucky Derby and then be disqualified. After many appeals Forward pass was named the winner.To this day controversy surrounds the 1968 Kentucky Derby. Bute was legal on most tracks around the country in 1968 and was legal at Churchill Downs the year before and after. Also, in the weeks prior to the race Peter Fuller had given his purse to Coretta Scott King the widow of slain Civil Rights activist Martin Luther King Jr. an act that brought on much praise and criticism. Martin Luther King Jr. had set up a sit-in on the Kentucky Derby the year before.
Trivia
- Oxyphenbutazone is the highest scoring word in Scrabble.
References
External links
"Phenylbutazone"