Relapse prevention of panic disorder in adult outpatient responders to treatment with venlafaxine extended release

Objective: To compare the long-term efficacy of venlafaxine extended release (ER) with placebo in preventing panic disorder relapse in outpatient treatment responders. Method: Outpatients aged >= 18 years who met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, criteria for panic disorder with or without agoraphobia for at least the previous 3 months, with >= 6 full symptom panic attacks in the 2 weeks prior to screening and >= 3 in the 2 weeks before baseline and a Clinical Global Impressions-Severity of Illness rating >= 4 at screen were eligible to participate. Outpatients received flexible-dose (75-225 mg/day) venlafaxine ER for 12 weeks. Treatment responders were randomly assigned to venlafaxine ER or placebo for 26 weeks. Criteria for response were <= 1 panic attack per week during the last 2 weeks of open-label treatment and a Clinical Global Impressions-Improvement score of 1 or 2. The primary endpoint, time to relapse during double-blind treatment, defined as >= 2 full symptom panic attacks per week for 2 consecutive weeks or discontinuation due to loss of effectiveness, was evaluated using Kaplan-Meier survival analysis. The study was conducted between December 2001 and August 2003. Results: The intent-to-treat population had 291 patients in the open-label phase and 169 in the double-blind phase (placebo, N=80; venlafaxine ER, N=89; mean daily dose 165-171 mg). Time to relapse was significantly longer with venlafaxine ER than placebo (p<.001). All secondary measures of panic attack treatment efficacy, quality of life, and disability were significantly better with venlafaxine ER than placebo (p <=.005). Conclusion: Venlafaxine ER was safe, well tolerated, and effective in preventing relapse in outpatients with panic disorder.