Vistaril (hydroxyzine) may be prescribed by your doctor to treat anxiety and tension, sleep problems or both. It is a sedative which reduces activity in your central nervous system. It has been shown to be effective in treating generalized anxiety disorder (GAD), which is characterized by chronic and exaggerated worry even when there is nothing to worry about. In one study in the Journal of Clinical Psychiatry, more than 300 patients with GAD who took hydroxyzine (the active ingredient in Vistaril), for 12 weeks, had an improvement in anxiety symptoms comparable to benzodiazepine, the active ingredient in Valium. They concluded that it is a safe and effective alternative to that class of drugs.