Buster is a fine cat (with humans) but his socialization skills with other cats has been problematic. He gets along fine with the cats that proceeded his arrival but the introduction of new cats has been a disaster. We have tried all the suggestions to make the introductions polite, but have been rewarded with rolling balls of fighting cats, chewed ears and ungodly sounds. Buster is always the aggressor in these spats. His nemesis is a playful and curious female cat named Paris (named after the city, not the actress) who drives him crazy. Both cats are neutered so it doesn't appear to be a hormonal thing, but Buster started the disgusting habit of spraying to mark his indoor "territory". Buster was well on the way to becoming an full time outdoor cat.
I decided it was time to try to unravel the mysteries of his mind, so I purchased a product named Feliway that mimics feline facial pheromones and is supposed to calm cats and prevent furniture scratching and spraying. When a cat rubs his face against you it is releasing a calming "happy" pheromone. Unfortunately this did not work.
The next treatment for Buster was the administration of female hormones. I figured that Buster needed to get in touch with his feminine side. This did seem to have an effect for a day or two, while Buster tried to figure out his sexual identity but after a while he was back to making Paris's life one of running an hiding, more fur and more broken pottery.
Thankfully my vet did some research and suggested antidepressent medication. Buster is now on a drug regimen using the human anxiety drug Amitriptyline. I had to sign for this when I picked up his prescription (made out to Buster Cat Poltrack). The side effects are pretty scary, I have to make sure that Buster doesn't have any suicidal thoughts, but so far he's acting pretty mellow. He did chase Paris the other day, but it was obvious that he meant no harm. Every evening we reenact a scene from One Flew Over the Cuckoo's Nest dispensing Buster's meds in his cat food.