Veterinarians have been a privilege to use and prescribe FDA approved drugs in an extra label manner and to compound drugs
to meet the specific health care needs of the diverse patients. Veterinarians that work with livestock species need to be
sure that the drug regime that they prescribe is not only safe for their patients but also for the end consumer that will
utilize the meat, milk and eggs for nourishment. It is important that food veterinarians understand not only the pharmacokinetics
of their treatment regimes but also the rules and regulations concerning extra label drug use (ELDU) and compounding.
Extra label drug use
Figure 1. Extra Label Drug Use Algorithm
The Animal Medicinal Drug Uses Clarification Act (AMDUCA) of 1994 as described in the code of federal regulations (21 CFR
Part 530) gave veterinarians the legal right to use FDA approved drugs in an extra label manner within a valid veterinary-client-patient
relationship. With this privilege came added responsibility for veterinarians. Specific label requirements include Name
and Address of veterinarian, Name of drug, Directions for use, Cautionary statements, and specified withdrawal for food animals.
Additionally, FDA requires that records of ELDU be maintained for 2 years. Record requirements include Identifying animal
or group, Species, Number treated, Condition being treated, Name of drug, Dosage prescribed, Duration of treatment, and the
Specified Withdrawal. Any drug that has been prohibited for use in food animals is also prohibited from extra-label usage
in food animals. Currently, there are 10 drugs or drug classes that are either prohibited or prohibited from ELDU in food
animals. These prohibited drugs are Diethylstilbestrol, Chloramphenicol, Nitromimidazoles, Nitrofurans, Clenbuterol, Sulfonamide
use in lactating dairy cattle, Dipyrone, Fluoroquinolones, Glycopeptides, and Phenylbutazone in lactating dairy cattle. Additional
restrictions include all medicated feed is restricted from ELDU and that ELDU is for treatment for health reasons not for
production enhancement. The AVMA developed an algorithm to assist veterinarians in making proper ELDU decisions (Figure 1).
Extra label usage applies to any use of a drug that is not in accordance with the approved label. This uses could include
species not listed in the labeling, use for indications not in the labeling, and use at dosages, frequencies or route of administration
not listed in the labeling. Whenever drugs are used extra label the veterinarian must establish an extended withdrawal supported
by appropriate scientific information.