Man Injects Dog, Etc.
The US Food & Drug Administration has, in fact, a Center for Veterinary Medicine. And the US Department of Agriculture regulates "vaccines, bacterins, antisera, diagnostic kits, and other products of biological origin" at its Center for Veterinary Biologics.
Stress is placed on the therapeutic use of human drugs in a standard veterinary/client relationship, where drugs are administered only under the care and advice of a vet. In a perfect world, the American Veterinary Medical Association guidelines for antimicrobials would be followed to the letter. But that's sometimes countermanded by our seemingly universal guideline, "If one is good, two is better" that governs such things as the application of home pesticides, or sharing Grandma's medicine because it works for her ...
The emphasis on regulating drugs entering the food chain is a good start. We often seem prone, however, to allowing a drive for profit or personal satisfaction to override both common sense and the law. I guess that's why the "duh" principle is seen at work, when the FDA must issue a guideline prohibiting the use of human anti-influenza drugs in poultry, in the face of avian flu epidemic scares.