A person, other than a veterinarian or an employee of a veterinarian, must not make extra-label use of a veterinary drug in or on a food-producing animal, unless permitted by the prescription of a veterinarian. A veterinarian may prescribe the extra-label use of a drug if:

(1) the veterinarian makes a careful medical diagnosis within the context of a valid veterinarian-client-patient relationship;

(2) the veterinarian determines that there is no marketed drug specifically labeled to treat the condition diagnosed, or that drug therapy as recommended by the labeling has, in the judgment of the attending veterinarian, been found to be clinically ineffective;

(3) the veterinarian recommends procedures to ensure that the identity of the treated animal will be carefully maintained;

(4) the veterinarian prescribes a significantly extended time period for drug withdrawal before marketing meat, milk, or eggs; and

(5) the veterinarian has met the criteria established in Title 21 of the Code of Federal Regulations, Part 530, which define the extra-label use of medication in or on animals.