The key here is to find a good vet, and then trust his/her opinion on the matter.
As a side note, if a physician or a veterinarian gets any sort of kickback from a pharmaceutical company the patient should be notified in writing. If there isn’t such a law, there should be.
Addendum to my post #2.
In the case of a vet, the owner should be notified, not the patient. I say that because my cat doesn’t care much for notifications one way or the other.
The exception is when the notification involves cat treats.