We have a cat with behavior problems, and on his second visit to the vet, he was not happy at all, being very aggressive. The vet and his assistant tried to put a leather muzzle on him without success, but after that, he went absolutely nuts, but they finally managed to put him in a thing that looked like a panini press with nets (don't know what is called), but still wiggling too much for the vet to be able to examine him well. The third visit was better, probably because the vet gave up on examining him (It was his annual and the vet gave him a shot, but that's all he could do, with no physical exams). They gave us a sedative to give him for the next visit (or was it for us to take so we don't get stressed out?), but now, I'm wondering how I will pill the boy. My DH was bitten once by him and he had to go through a round of IV antibiotics, so you understand our reluctance in trying to open his mouth. Even with a pilling device, someone will have to open his mouth...
We knew he would be a challenge when we got him because nobody wanted him at Human Societies for months due to his behavior problems. He has gotten better over the years, but still, he is not easy to handle, and he probably never will be.
Just so you all know, he is loving in his own way. He likes to give my DH's arm a bath when my DH is waking up. He now purrs (not my DH, my cat) a little once in a while when he's with my DH (He's never purred around me.)
I just hope he doesn't get seriously sick. I cannot imagine pilling the boy every day, or giving him a fluid injection every day.
One thing we've noticed though is that he is more tolerable when he wants to be fed, like if we're late giving him lunch. I can hold him and bug him a little and he doesn't retaliate as much, so maybe that's my chance.