The tranquilizing drug Valium (generic name diazepam) has been around for years, and many a nervous, stressed-out person is thankful for it. It is widely used by veterinarians to treat cats—not for nervousness but for aggression. It is effective with most overly aggressive cats, though in a few cases it actually seems to make the cat more aggressive. Note: do not try to administer your own Valium to your cat. The dosages for cats are different than dosages for humans, and this matter needs to be handled by a vet.