Management of treatment-resistant panic disorder.

Panic disorder (PD) is a severe, chronic disorder characterized by one or more unexpected panic attacks followed by worry about additional attacks and/or the implications of the attacks. If attacks are sufficiently severe or frequent, they can promote marked, sometimes debilitating behavioral changes. Many panic disorder sufferers appear to be incompletely responsive to treatment and are subject to relapse after remission. In this article, we highlight the current understanding of the pathophysiology of PD using a "fear circuit" model. Using this model as a reference point, we review the evidence base supporting existing and emerging treatments and suggest strategies for optimizing initial treatment response. Finally, a differential diagnostic approach for clinical evaluation of unsatisfactory response to treatment in PD is presented.