Phenylbutazone Added to Prohibited List

Dr. Clell V. Bagley
USU Extension Veterinarian

Effective May 29, 2003, the Food and Drug Administration (FDA) will prohibit extralabel use of phenylbutazone animal and human drugs in female dairy cattle 20 months of age or older. The FDA is issuing the order based on evidence that extralabel use of phenylbutazone in female dairy cattle 20 months of age or older will likely cause an adverse event in humans. With this action the use of any phenylbutazone in an adult dairy cow becomes a violation of the Food, Drug and Cosmetic Act and one of FDA's highe

With the May 29, 2003, implementation of this order, the list of drugs prohibited from extralabel use in food animals (in chronological order of prohibition) will be:

Chloramphenicol
Diethylstilbestrol (DES)
Nitroimidazoles - (including dimetridazole, metronidazole and ipronidazole)
Sulfonamide use in adult dairy cattle*
Clenbuterol
Dipyrone**
The fluoroquinolones - (examples enrofloxacin and danofloxacin)
The glycopeptides - (example vancomycin)
Nitrofurans - (including nitrofurazone, furazolidone, topical use prohibited as well)
Phenylbutazone use in adult dairy cattle*
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*Lactating (adult) dairy cattle are defined by FDA as dairy cattle 20 months of age or older regardless of whether they are milking or dry. Currently, the only sulfonamide available for use in dairy cattle older than 20 months of age is sulfadimethoxine (SDM). In adult dairy cattle this drug may only be used on-label. Administering higher doses or sustained release SDM products is prohibited. Aside from the above AMDUCA list, regulations related to the Pasteurized Milk Ordinance (PMO) prohibit the

** Because dipyrone-containing products are not available for either humans or animals, it is not typically included on lists of extralabel prohibitions published by CVM. However, old stockpiles of the drug do occasionally surface. Any use of dipyrone in food animals remains a violation of the Food Drug and Cosmetic Act.