Efficacy of d-cycloserine for enhancing response to cognitive-behavior therapy for panic disorder

Traditional combination strategies of cognitive-behavior therapy plus pharmacotherapy have met with disappointing results for anxiety disorders. Enhancement of cognitive-behavior therapy with d-cycloserine (DCS) pharmacotherapy represents a novel strategy for improving therapeutic learning from cognitive-behavior therapy that remains untested in panic disorder.

This is a randomized, double-blind, placebo-controlled augmentation trial examining the addition of isolated doses of 50 mg d-cycloserine or pill placebo to brief exposure-based cognitive-behavior therapy. Randomized participants were 31 outpatients meeting DSM-IV criteria for panic disorder with or without agoraphobia, who were offered five sessions of manualized cognitive-behavior therapy emphasizing exposure to feared internal sensations (interoceptive exposure) but also including informational, cognitive, and situational exposure interventions. Doses of study drug were administered 1 hour before cognitive-behavior therapy sessions 3 to 5. The primary outcome measures were the Panic Disorder Severity Scale (PDSS) and Clinicians' Global Impressions of Severity.

Results indicated large effect sizes for the additive benefit of d-cycloserine augmentation of cognitive-behavior therapy for panic disorder. At posttreatment and 1 month follow-up, participants who received d-cycloserine versus placebo had better outcomes on the PDSS and global severity of disorder and were significantly more likely to have achieved clinically significant change status (77% vs. 33%). There were no significant adverse effects associated with DCS administration.

This pilot study extends support for the role of d-cycloserine in enhancing therapeutic learning from exposure-based cognitive-behavior therapy and is the first to do so in a protocol emphasizing exposure to feared internal sensations of anxiety in panic disorder.