I'm glad you trust your vet, truly, this these are easier to deal with with a good vet. I"m really sorry you and your cat are going through this. I lived through a minor version of it, which is behind my previous advice. No judgment period you are the one living this and it is hell.
We had a very anxious elderly dog and rather than prozac we tried various things that worked randomly for heavan's sake and made it where she couldn't walk. That was NOT helpful. Got a new vet who gave her Clomicalm by Novis. It worked and it worked fast. I read other reviews where it worked for cats. One I remember was where the cat wouldn't stop biting the baby until it took the pills. One thing to note, while we were giving it to our dog, Novis screwed up their mfg and put the wrong size pills in the bottles. They were the correct medicine but the wrong dosage. They had to shut down for awhile and the price went illegally high. So I'd be sure to have a bottle of low dose to wean kitty off of it if need be. Explain this to your vet, he probably remembers this mess.
Here is an addy, there are many, about Clomicalm and cats.
Clomipramine (Clomicalm, Anafranil) - Veterinary Partner - VIN
We had a very anxious elderly dog and rather than prozac we tried various things that worked randomly for heavan's sake and made it where she couldn't walk. That was NOT helpful. Got a new vet who gave her Clomicalm by Novis. It worked and it worked fast. I read other reviews where it worked for cats. One I remember was where the cat wouldn't stop biting the baby until it took the pills. One thing to note, while we were giving it to our dog, Novis screwed up their mfg and put the wrong size pills in the bottles. They were the correct medicine but the wrong dosage. They had to shut down for awhile and the price went illegally high. So I'd be sure to have a bottle of low dose to wean kitty off of it if need be. Explain this to your vet, he probably remembers this mess.
Here is an addy, there are many, about Clomicalm and cats.
Clomipramine (Clomicalm, Anafranil) - Veterinary Partner - VIN