A recent question Cat suddenly became paralyzed has a cat with sudden onset paralysis, after starting a new drug. The companies drug literature does not list this as a side effect, but the OP found that several pet owners had seen paralysis after administering the drug.

although I did find pet-owners who had the same experience on related forums.

User comments suggest that as the side effect is not listed by the manufacture it could not possibly be related 1 & 2

You've done the research and there really isn't any reason to think there's a link between the felimazole and your cat's new symptoms.

I'm referring to the listed side-effects from studies.

What are the actual legal requirements for pet medications? Does the vet or the manufacture need to report this possible side effect?

  • 1
    this site might provide some of the information fda.gov/animalveterinary/resourcesforyou/ucm268128.htm Oct 12, 2018 at 7:44
  • 1
    @trondhansen thank you, a side link from your source seems to indicate the answer, which is what my early research showed. I was really hoping someone would post a "yes, there is a requirement" answer. Oct 12, 2018 at 16:56
  • in the EU adverse effects are listed for each type of medication by the producers like this for felimazole noahcompendium.co.uk/… but this do not answer what the regulations in the US are. Dec 27, 2018 at 8:42

1 Answer 1


As far as I can tell, reporting is completely voluntary.

The FDA encourages veterinarians and animal owners to report adverse drug experiences and product defects associated with animal drugs or animal devices souce emphisis mine

There are no requirements for drug makers or veterinarians to report side effects.

You can't prove a negative, so this remains an open question. I will happily modify or delete this answer if reputable sources for mandatory reporting are found.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.