Coping With Feline Aggression

my 4 year old shorthair has suddenly began chasing and biting his tail,he screams and hisses when he gets it. when walking it seems when he catches sight of it,it scares him and he starts to run or goes in circles until he captures it and then bites it. He seems to be quite agitated, and does alot of pacing about until he gets tired and then goes to sleep. He has not been aggressive with me. My vet first put him on phenobarbital, now he is on prozac,it takes about 10 days to get in his system. He is normally good natured but does not like to be picked up and sometimes when petting him he will scratch you. He is somewhat high strung not like his brother who is very laid back. He is the dominate cat over his brother. Any suggestions? Any help? It is very heartbreaking to see him doing this to himself.