Hi, I have 3 of my 8 cats on Prozac, each for different reasons, and it seems to be working well for all of them.
I put Duck on Prozac for a few reasons - one, inappropriate urination. She went from peeing on bathmats and my office rug to peeing in the bathroom sink. She hasn't done that since taking Prozac. She is also my largest cat and has some issues with jealousy and aggression. She was picking on my smallest cat, who was too frightened to defend herself. If Duck saw another cat getting attention, she'd get upset and smack them. She's much less aggressive now, but still very affectionate and full of personality.
Turtle, my smallest cat, went on Prozac for fur pulling. She's my only longhair, and I would see her grab large mouthfuls of her fur and PULL, ripping it out. I found clumps of her fur all over my house, and her sides were all but bald. She is scared of Duck, won't fight back when she's attacked, but either run away or run to me. Since Prozac, she's still nervous, but the fur pulling has gone down about 95%.
Louie is also on Prozac. I think he may have some sort of separation anxiety, and he tends to get VERY pushy when he wants attention. Normally that's fine, but since I started working from home, he didn't like me being there and not giving him attention. If I shut him out of my office, he literally cried, scratched at the door and howled for 8 hours straight. If I let him in, he jumped up on the desk in front of my computer and I can't have that during video calls. I would put him on the floor and he'd jump back up again. We'd do this 10-15 times in a row. Now he's much more mellow, not nearly as needy and desperate for attention, but still extremely affectionate.
The original RX was just for Duck, 5mg twice a day. That seemed to be way to much, so I cut it down to 2.5 mg twice a day. She still seemed a bit over medicated to me, so now she just gets 2.5 once a day. That's the same dose I put Louie and Turtle on too (they're both much smaller than Duck) and it seems to work great for all of them.
According to my vet, Prozac is a great drug for cats. There are no side effects, no withdrawal symptoms if you take them off of it, and it works really well. I've had pretty good luck with it. :-)
Hope this helps!