That's very different than saying extra label drug use is not allowed, or saying that one can never eat the eggs after using ivermectin, fenbendazole, albendazole, piperazine, etc, which I have seen people do.
I believe what I am saying may be misconstrued.
I am merely quoting the current FDA approved drugs for laying hens (2017), correcting an older listing that was posted in the first post from 2015, as the approved drugs have changed....the topic of the original post..."Approved FDA Drugs"
FARAD makes clear suggestions to vets in this publication:
https://vet.osu.edu/sites/vet.osu.edu/files/documents/extension/Egg residue considerations during the treatment of backyard poultry 2015.pdf
It is clear the FDA considers "pet" chickens as still food producing and instructs vets they should follow guidelines for drugs for food producing animals for backyard chcikens per FDA listings.
A drug is either approved or not approved, per the regulating authority in the US, the FDA....that can be considered "legal" or not, but the term is FDA approved. (Legal becomes semantics...whether or not legal proceedings could incur if a person has not upheld a written law or rule...FDA carries force of law with its administrative rules).
If you are a commercial poultry owner (over 3,000 birds), you come under regular inspection for which the FDA will enact penalties should residue of un-approved drugs be found.
If your a small holder (back yard owner), you can do whatever you want for personal use, as well as other, with the understanding that if an un-approved drug residue were ever found in your eggs that were sold or shared with the public (non immediate family), especially under food-illness situations, you are still liable for the FDA penalties.
Vets must consider any legal ramifications for themselves and their clients as their licensing requires them to uphold laws and administrative rulings, to the best of their abilities, thus instructing their clients appropriately.
Again, we are dealing with FDA rulings (which change), vet ethical and legal licensing requirements (which is somewhat interpretive, thus the FARAD publication), and personal risk comfort for the small holder.
Most back yard holders simply withdraw eggs according to the FARAD pull times to avoid any residue being found in their eggs. Some don't care, don't withhold, share at will.
It is all about the residue in the eggs...if un-approved drug residue is found, ETA (and zero tolerance is the norm in the US), then you could/would be liable for any FDA penalty. The only certain way to avoid the risk from penalty of drug residue ever being found is to never use the hen again for food production if the drug is not FDA approved....because of the FDA's "zero tolerance" levels...that is the "technical" answer...which I've stated before is often "winked" at by using withdrawal times.
Vets are becoming more reluctant to administer off label drugs for chickens because of the FDA approach to animals who also produce food (eggs).
There are clearly some banned drugs which are completely illegal to use in the US which would bring harsher penalties if used in animals, see the FARAD publication linked.
Just information for those who care to use as they see fit....my intent was to merely clarify new rulings have changed the "Approved" drugs by the FDA in the US.
LofMc
https://vet.osu.edu/sites/vet.osu.edu/files/documents/extension/Egg residue considerations during the treatment of backyard poultry 2015.pdf