Succi
Succinylcholine is a myorelaxant and is used in surgery for intubations. There is no way PF could have it as he, sorry, was a farrier and neither a veterinarian not a doctor. If he had access to it, this in itself is highly illegal, and DEA would be on his case as it is a prescribed substance.
PF is a layman with no vet diploma. OK, he trims hoofs of animals. He has high school education. He has no training to use sedation on animals, tbh. Even use of pharmaceuticals to sedate animals by a person without veterinarian diploma is, probably, illegal.