Intercat Aggression between cats is a difficult problem. In some cases it seems almost unresolvable. I have several clients who have finally just resorted to keeping their cats in separate parts of the house, all the time.
We have used medications for these problems and some of the time they either worked or the cats finally worked out their problems. It is always hard to tell which of those two possibilities really happened.
Amitriptylline is sometimes helpful when given to the aggressor cat. It is used by giving 5mg twice a day or 5 to 10mg once a day (the recommendation seems to vary and may be based entirely on the cat's response to medication).
Anti-anxiety medications can be helpful when given to the cat who is being attacked, If the cat reacts with a great deal of nervousness or hair-raising and running away. That sort of behavior tends to egg on the aggressor cat. By using an anti-anxiety medication like diazepam (Valium Rx) or buspirone (Buspar Rx) in the "victim" cat to reduce these behaviors, the attacking cat may be less likely to be stimulated to attack.
In general, cats do not have the social structure that dogs do, so dominance behavior is less likely in them. Most cat disputes are territorial, predatory aggression that is redirected, or fear based. Sometimes play behavior in cats can look pretty rough, too. Many cats do not become territorial until they are 2 to 5 years of age. Unfortunately, these behavioral patterns are a problem when cats must live together indoors.
Dr Mike Richards, DVM
Michael Richards, D.V.M. co-owns a small animal general veterinary practice in rural tidewater Virginia. Dr. Richards graduated from Iowa State University's College of Veterinary Medicine in 1979, and has been in private practice ever since. Dr. Richards has been the director of the PetCare Forum...