A cat tranquilizer is a medication that is useful in calming a cat that is frightened or injured. It is also used for alleviating the anxiety that accompanies stressful events, such as moving or traveling, according to WebMD. Acepromazine and diazepam are examples of tranquilizers for felines.
Acepromazine relieves anxiety in cats and has a depressive effect, WebMD states. The use of diazepam is preferred over acepromazine because diazepam's depressive effect is less pronounced, but diazepam can produce serious liver problems when used for long periods of time.
Because tranquilizers block inhibitory responses in cats, WebMD warns that tranquilizer use may cause undesirable behaviors, including unprovoked biting and scratching and failure to use the litter box. Using tranquilizers for long-term behavior modification is not recommended.