Code of Federal Regulations Title 21. Food and Drugs § 21.530.11 Limitations

(a) Extralabel use in an animal of an approved new animal drug or human drug by a lay person (except when under the supervision of a licensed veterinarian);

(b) Extralabel use of an approved new animal drug or human drug in or on an animal feed;

(c) Extralabel use resulting in any residue which may present a risk to the public health;  and

(d) Extralabel use resulting in any residue above an established safe level, safe concentration or tolerance.