Dr. Clell V. Bagley, D.V.M.
USU Extension Veterinarian
The Animal Medicinal Drug Use Clarification Act (AMDUCA), signed into law in 1994, amended the Food Drug and Cosmetic Act to decriminalize most instances of Extralabel Drug Use by veterinarians. This privilege, however, is not carte blanche; specific conditions must be met before a veterinarian may legally use or prescribe drugs in an extralabel fashion for food-producing animals. These requirements include a valid veterinarian-client-patient relationship and appropriate drug labeling and record keeping.
Certain drugs may not be prescribed or used even under AMDUCA auspices.
Thus far, FDA-CVM has prohibited eight drugs or drug classes, making their extralabel use in food animals illegal.
Veterinarians violating state or federal laws regulating the transport, sale, or use of drugs may face various sanctions, including warning letters, fines, temporary or permanent revocation of their state veterinary license, or incarceration. Extralabel use of any of the prohibited drugs in food animals represents one of the FDA’s highest priorities for regulatory attention.
Prohibited Drugs:
- Diethylstilbestrol (DES)
- Chloramphenicol
- Nitroimidazoles - which include dimetridazole, metronidazole, and ipronidazole.
- Sulfonamide use in dairy cattle - Only 1 of the 3 sulfonamides that have label indications for lactating cows, sulfadimethoxine (SDM), is currently being marketed. Currently, use of any sulfonamide other than SDM in dairy cattle older than 20 months is illegal. Additionally, extralabel use of SDM in lactating dairy cattle is prohibited (for example, use of a higher dose or slow-release SDM boluses in dairy cattle is not permitted).
- Nitrofurans
- Clenbuterol
- Dipyrone - Because products are not available for either humans or animals, dipyrone is not typically included on lists of extralabel prohibitions published by FDA-CVM. Old stockpiles of the drug, however, do occasionally surface. Any use of dipyrone in food animals remains a violation of the Food Drug and Cosmetic Act.
- Fluoroquinolones - Although data have not been sufficiently conclusive to prevent approval of sarafloxacin for chickens and beef cattle, it prompted FDA-CVM to prohibit extralabel use of these compounds in 1997. Fluoroquinolone products labeled for either humans or companion animals may not be used in food animals. Any deviation from a food animal label (such as use with a different species, dosage, route of administration, or disease indication) is similarly illegal. In the case of the approved beef cattle formulation of enrofloxacin (Baytril 100), this prohibition extends to all nonbeef-production animals, including lactating and nonlactating dairy cows, heifer replacements, and veal calves. Enrofloxacin may not be stored in dairy farm drug cabinets.
- Glycopeptides - The only glycopeptide antibiotic available in the United States is the human product vancomycin (Vancocin). Vancomycin is often the treatment of last resort for methicillin-resistant Staphylococcus aureus (MRSA) infections in humans. Avoparcin, a compound chemically similar to vancomycin, has been used in European animal feeds as a growth promoter since the mid-1970s. FDA-CVM in 1997 issued an order prohibiting the extralabel use of all glycopeptides in food animals. The restriction of fluoroquinolone and glycopeptide use represents a novel exercise of FDA-CVM discretionary authority: restriction based not on the drug’s direct toxicity, but on its potential for increasing human pathogen resistance.
- Extralabel use of medicated feed - Section 530.11 of AMDUCA specifically prohibits the “extralabel use of an approved new animal drug or human drug in or on an animal feed.” As a matter of enforcement discretion, FDA-CVM generally has not objected to mixing a drug with an individual animal’s feed, but extralabel mass medication in feed is prohibited “without limitation or exception.” This prohibition extends to all drugs; not just those discussed in this article.
- Other dairy prohibitions - With the exception of SDM, none of the drugs or drug classes listed may be legally labeled for dairy cattle and, if found during an inspection, would trigger regulatory action. In addition to dipyrone, there are two drugs that are not currently on the AMDUCA prohibited list but which result in “debits” if found during a dairy inspection. These are dimethyl sulfoxide and collodial silver. The use of ionophore compounds (i.e., monensin, lasalocid) in lactating dairy cattle rations is prohibited.
- State of aminoglycosides - A number of veterinary organizations have established or support policies that discourage the extralabel use of aminoglycosides. These position statements are nonbinding and should not be confused with the legal prohibitions described.
- Treatment of companion animals - The prohibitions described in this article pertain to food-producing animals only and not companion species, such as dogs and cats.
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