With the constant infusion of new products to the human and veterinary market, it becomes a daunting task to keep up with
veterinary pharmacology and vaccine technology.
And although all veterinarians have the responsibility of safe and prudent drug use in animals, food animal veterinarians
have the added responsibility of residue avoidance. Most food animal practitioners are aware of the Animal Medicinal Drug
Use Clarification Act (AMDUCA), but understanding what is actually allowed and what is not allowed can be difficult.
This article will discuss the sometimes confusing rules and regulations of prudent drug use in food animals and provide resources
that food animal veterinarians can use to find information.
AMDUCA allows for extra-label drug use in food animals. But what is extra-label use? It is using a drug:
1) in a food animal species that is not on the label,
2) for an indication that is not on the label,
3) at a dose level, frequency or duration that is not on the label,
4) by a route of administration that is not on the label,
5) in a class of food animal that is not on the label.
So, using a drug in a goat that is only labeled for cattle is extra-label use. Using a drug in a dairy cow that is only labeled
for beef cattle is extra-label use. Using a drug in a lactating dairy cow that is only labeled for non-lactating cows is extra-label
There are constraints associated with extra-label drug use under AMDUCA. Two of the most important are that extra-label use
must be by or on the order of a veterinarian within the context of a veterinarian-client-patient relationship (VCPR), and
that extra-label use must not result in violative residues in food-producing animals.
For example, producers are not allowed to increase a dose of a drug, even if it is an over-the-counter product. Only a licensed
veterinarian can do that. And veterinarians must have a valid VCPR even to prescribe drugs on label. For example, advising
an unknown producer to give a dose of penicillin that is higher than the label indicates is not permitted, even though this
is an over-the-counter drug.
If a drug is prescribed in an extra-label manner, a withdrawal time must be established that prevents violative residues.
Some resources to help establish proper meat and milk withdrawal times are the drug manufacturer for the particular product
and the Food Animal Residue Avoidance Databank (FARAD) at
Other constraints to extra-label drug use in food animals include: the drug must not be on the prohibited list (see the next
section); and there must not be any drug(s) labeled for use in food animals that has the needed ingredient, in the proper
dosage form, is labeled for the indication and is clinically effective.
Knowing when a human-approved drug can be used in a food animal is a common dilemma. AMDUCA states that extra-label use of
human-approved drugs is not permitted if a drug approved for food animals exists that can be used in an extra-label manner.
So, for instance, if a cephalosporin is indicated for a condition in a food animal, like neonatal septicemia in a calf, the
veterinarian must use ceftiofur because it is labeled for food animals, even though not for neonatal septicemia. If in this
case culture results indicate there are no food animal drugs that would be appropriate, then another veterinary or human drug
would be permitted for use.