Studies have shown that antidepressants are effective in reducing or eliminating panic attacks and improving anticipatory anxiety and symptoms of agoraphobia. Unfortunately, antidepressants generally don’t result in an immediate relief of symptoms. Most people will not see a significant improvement for at least 4 weeks. Studies have generally shown that the full benefits of antidepressant therapy may take as long as 8 to 12 weeks. However, this timeline is variable among individuals. For people with severe anticipatory anxiety and agoraphobic avoidance, symptoms may not show significant improvement for 6 months or longer, but this is not necessarily because it takes longer for the medication to work -- severe disease is simply harder to treat and will take more time.
Some people may experience increased nervousness or anxiety in the beginning of antidepressant therapy. To reduce this possibility, your doctor may start you at a very low dose that is gradually increased. Your doctor may also prescribe a benzodiazepine (anti-anxiety medication) along with your antidepressant, especially in the beginning of treatment. Once the antidepressant reaches its full benefit, the benzodiazepine is often no longer needed on a regular basis.
If you and your doctor believe that you have had an adequate trial of antidepressant therapy without significant improvement of symptoms, a medication change may be made. For the vast majority of panic disorder sufferers, the right medication will be found to improve or eliminate panic symptoms.
American Psychiatric Association. Practice Guidelines for the Treatment of Psychiatric Disorders: Compendium 2006. American Psychiatric Association, 2006.