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Thanks for your question, Elliott.  I am not a prescriber, so it would be great if others weighed in on your question, but one place you might want to start is FDA's Guidance For Industry (GFI) #152,Evaluating the Safety of Antimicrobial New Animal Drugs with Regard to Their Microbiological Effects on Bacteria of Human Health Concern.  This has been known as "Appendix A", and FDA has been updating the guidance.  You can read more about that and download a draft version here.

Hello Elliot,

Though I'm not a prescriber either - are any of the pharmaceuticals you're referring to classified as ionophores or coccidiostats? These are sometimes referred to interchangeably, but are technically two distinct drug classes with significant overlap. Differing names for these and other drugs across different jurisdictions and localities, especially considering different trade names, may be a source of confusion. Common ionophores can be found listed on page 6 of the OIE/WOAH resource listed below.

Though they have antimicrobial effects in that they kill or prevent the growth of microbes, it's my understanding these drugs generally aren't used in human medicine outside of experimental anti-cancer research. Due to this extremely limited use in humans, these aren't often thought of as substantially impacting human health. However, co-selection of coccidiostat resistance with AMR relevant to humans has been investigated as a possible effector of public health. Inversely, consequences of coccidiostat removal on production systems, and resultant incentivization of using antimicrobials relevant to human health, has been considered as well. Several are still labelled for growth promotion (the exact label language escapes me) in the United States. The FDA does classify ionophores as antimicrobials in their sales/distribution reporting on veterinary antimicrobials, but these are considered not medically important alongside several other drug classes. See more at the bottom of the chart shown here. I believe the EU and many other jurisdictions do not classify these drugs as antimicrobials. I'm not as familiar with the other non-medically important antimicrobials listed by the FDA.

I'm not sure if the resources below completely capture what you are trying to find, but they may be of some help, if you weren't aware of them already:

• The OIE [now WOAH] List of Antimicrobial Agents of Veterinary Importance (2021)
  • Drugs classified as Veterinary Important Antimicrobial Agents (VIA), Veterinary Highly Important Antimicrobial Agents (VHIA), or Veterinary Critically Important Antimicrobial Agents (VCIA)
• European Medicines Agency Categorisation of antibiotics for use in animals for prudent and responsible use (2019)
  • Drugs classified as avoid, restrict, caution, and prudence

In addition to their newly updated list of medically important antimicrobials, the WHO's previous materials on their AWaRe (Access, Watch, Reserve) classifications (2021-22) and, even earlier guidelines on use of medically important antimicrobials in food-producing animals (2017), may be of relevance. It sounds like you might be using the Codex Alimentarius' resources on residue limits, but I thought I might link it here in case helpful.

Searching language related to many of the materials listed above should provide a wide variety of supplemental documentation that may aid your work.

I hope this can be of some use to you, and I'd be more than happy to hear the thoughts of any others as well. I would also be highly interested in seeing any research outputs you may plan to create. This is an active are of work for me, so please don't hesitate to reach out if you have any more questions or comments. Best of luck with your continued research.

Regards,

Neil V.