There are veterinary drugs which are poisonous to humans but useable for cattle, sheep, horses and other animals. Often these are preparations which were developed for humans but withdrawn when they turned out to have harmful side effects which either do not occur in animals, occur at a lower frequency or where the cost/benefit analysis ends up favouring their use. Many veterinary preparations are simply generic human preparations and can be safe to take for humans. The other way around is not as simple since many common human preparations are actively poisonous to animals. A single tablet of paracetamol (acetaminophen) or naproxen can be enough to kill a cat or a small dog, a few will kill a dog. Ibuprofen causes kidney damage in cats and dogs, etc.

So, yes, there are veterinary preparations humans should not use just like there are many more human preparations which should never be given to animals. Dosage can also differ between species. Many veterinary preparations are abused as narcotics, e.g. Ketamine and Xylazine. With all that said and with the required knowledge available there are many veterinary preparations which can be used by humans since they are either identical - e.g. Prascend (used to treat Cushing's disease in horses) is more or less identical to Permax (used to treat Parkinson's disease in humans, withdrawn from many markets), both have pergolide as active ingredient. Ivermectin is another example which can be found in many veterinary preparations as well as those for humans, often using a different base but otherwise identical. The extremely polarised debate around SARS2 and the use of Ivermectin have led to a proliferation of dire warnings about the differences between veterinary and human preparations so it is advisable to look for older texts when searching for information about these differences.

If I were to need medication and were offered the choice between a preparation made for human use and one for veterinary use I would choose the first one. If the choice were between a veterinary preparation and no medication and if I deemed the need to be sufficiently high I would take the veterinary preparation after having read up on the ingredients. If I were to need Ivermectin and were offered the choice to either get a box of 10 pills for €250 or a (new) syringe of Noromectin ('horse paste') for €5 (which is what these cost, thereabouts) I would take the horse paste without any qualms.