Paroxetine Hydrochloride, also known as PAXIL, is used to treat behavioral disorders such as obsessive-compulsive disorders (canine compulsive disorder) and dominance aggression. In cats, it has been effective for decreasing urine spraying. Category, Antidepressive. It is classified as a selective serotonin reuptake inhibitor (SSRI). It resembles fluoxetine (PROZAC) in action.