Phenylbutazone
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Phenylbutazone, often referred to as "bute",[1] is a nonsteroidal anti-inflammatory drug (NSAID) for the short-term treatment of pain and fever in animals.
In the United States and United Kingdom, it is no longer approved for human use (except in the United Kingdom for
Uses
In humans
Phenylbutazone was originally made available for use in humans for the treatment of rheumatoid arthritis and gout in 1949. However, it is no longer approved, and therefore not marketed, for any human use in the United States.[3] In the UK it is used to treat ankylosing spondylitis, but only when other therapies are unsuitable.[4]
In horses
Phenylbutazone is the most commonly used NSAID for horses in the United States.[5] It is used for the following purposes:
- tissue to control inflammation, thereby reducing secondary inflammatory damage, alleviating pain, and restoring range of motion. It does not cure musculoskeletal ailments or work well on colicpain.
- symptoms.
History of phenylbutazone in racing
In the 1968 Kentucky Derby, Dancer's Image, the winner of the race, was disqualified after traces of phenylbutazone were allegedly discovered in a post-race urinalysis. Owned by prominent Massachusetts businessman Peter D. Fuller and ridden by jockey Bobby Ussery, Dancer's Image was the first horse to win the Kentucky Derby and then be disqualified. Phenylbutazone was legal on most tracks around the United States in 1968, but had not yet been approved by Churchill Downs.
Controversy and speculation still surround the incident. In the weeks prior to the race, Fuller had given previous winnings to
Although Forward Pass had been named the winner, after many appeals the Kentucky Derby official website lists both Dancer's Image and Forward Pass as the winner. The website's race video commentary states that on the winner's plaque at Churchill Downs, both Dancer's Image and Forward Pass are listed as the 1968 winner of the Kentucky Derby.[8]
In dogs
Phenylbutazone is occasionally used in dogs for the longer-term management of chronic pain, particularly due to osteoarthritis. About 20% of adult dogs are affected with osteoarthritis, which makes the management of musculoskeletal pain a major component of companion animal practice. The margin of safety for all NSAIDs is narrow in the dog, and other NSAIDs are more commonly used (etodolac, and carprofen). Gastrointestinal-protectant drugs, such as misoprostol, cimetidine, omeprazole, ranitidine, or sucralfate, are frequently included as a part of treatment with any NSAID. Dogs receiving chronic phenylbutazone therapy should be followed with regular blood work and renal monitoring.[9]
Side effects of phenylbutazone in dogs include gastrointestinal (GI) ulceration, bone marrow depression, rashes, malaise, blood dyscrasias, and diminished renal blood flow.
Dosage and administration in horses
Phenylbutazone has a plasma elimination half-life of 4–8 hours, however the inflammatory exudate half life is 24 hours,[10] so single daily dosing can be sufficient, although it is often used twice per day.[5] The drug is considered fairly non-toxic when given at appropriate doses (2.2-4.4 mg/kg/day), even when used repeatedly.[11] This dose has been doubled for diseases that cause severe pain, such as laminitis, but is toxic if repeated long-term, and exceptionally high doses (15 mg/kg/d or higher) can kill the animal in less than a week.[12]
Phenylbutazone can be administered orally (via paste, powder or feed-in) or
Side effects and disadvantages
Side effects of phenylbutazone are similar to those of other NSAIDs. Overdose or prolonged use can cause
Phenylbutazone amplifies the anticoagulant effect of vitamin K antagonists such as warfarin or phenprocoumon. Phenylbutazone displaces warfarin from plasma binding sites, and toxic blood levels leading to haemorrhage can occur. It may aggravate kidney or liver problems.
Phenylbutazone may be
.Phenylbutazone can be used in foals. Premature foals, septicemic foals, foals with questionable kidney or liver function and foals with diarrhea require careful monitoring. Drugs to protect the GI tract such as omeprazole, cimetidine, and sucralfate are frequently used with phenylbutazone.
High doses of phenylbutazone may be considered a rules violation under some
The International Agency for Research on Cancer places it in Group 3; i.e., "not classifiable as to its carcinogenicity to humans".
Use in horses is limited to those not intended for food. Metabolites of phenylbutazone can cause
Investigations into potential carcinogenicity
Opinions are conflicting regarding the
Interactions
Other anti-inflammatory drugs that tend to cause GI ulcers, such as corticosteroids and other NSAIDs, can potentiate the bleeding risk. Combination with anticoagulant drugs, particularly coumarin derivatives, also increases the risk of bleeding. Avoid combining with other hepatotoxic drugs.
Phenylbutazone may affect blood levels and duration of action of
Overdose
Overdoses of phenylbutazone can cause
Chemistry
Phenylbutazone is a
-
Hydrazobenzene
-
Diethyl n-butylmalonate
References
- ^ Bogdanich W, Drape J (24 March 2012). "Death and Disarray at America's Racetracks". The New York Times.
- ^ "Horse meat investigation. Advice for consumers". Enforcement and regulation. Food Standards Agency. Retrieved 19 May 2013.
- ^ "FDA Order Prohibits Extralabel Use of Phenylbutazone in Certain Dairy Cattle". Food and Drug Administration. 28 February 2003.
- ^ NHS: Drugs used in Rheumatic Diseases and Gout Archived 2013-04-29 at the Wayback Machine
- ^ a b McIlwraith CW, Frisbie DD, Kawcak CE. Nonsteroidal Anti-Inflammatory Drugs. Proc. AAEP 2001 (47): 182-187.
- ^ Boston Globe article about the 40th Anniversary of the Race
- ^ "Sports: Dancer's tainted image". Archived from the original on 2007-01-01. Retrieved 2007-10-07.
- ^ "Kentucky Derby 132". 2006. Retrieved 2007-10-07.
- ^ "Wedgewood Pharmaceuticals-Phenylbutazol".
- PMID 3723663.
- PMID 6725103.
- ^ PMID 6869982.
- ^ Lees P, Higgins AJ. Clinical pharmacology in therapeutic uses of non-steroidal anti-inflammatory drugs in the horse. Equine Vet J 1985;17:83–96.
- ^ Scanaill PÓ. "Phenylbutazone and its availability in ireland – prudent prescribing and dispensing" (PDF). Irish Veterinary Journal. 63 (12): 766–8. Archived from the original (PDF) on 2012-04-02.
- ^ "Ante and Post-mortem Procedures, Dispositions, Monitoring and Controls - Red Meat Species, Ostriches, Rheas and Emus". Canadian Food Inspection Agency. 2013-05-31.
- PMID 3476793.
- PMID 7744695.
- PMID 8143623.
- ^ PMID 20720197.
- PMID 9838026.
- ^ IARC (1987). IARC monographs on the evaluation of the carcinogenic risk of chemicals to man. International Agency for Research on Cancer. p. 316.
- ^ a b "Phenylbutazol for veterinary use". Wedgewood Pharmacy.