Efficacy of Venlafaxine Extended-Release Capsules in Nondepressed Outpatients With Generalized Anxiety Disorder

ContextGeneralized anxiety disorder (GAD) is a chronic disorder that is associated with debilitating psychic and somatic symptoms. Venlafaxine extended-release (XR) capsules have been shown to be effective in short-term treatment of patients with GAD without major depressive disorder (MDD), but long-term data are needed to establish whether this agent confers persistent benefits.ObjectiveTo compare the 6-month efficacy and safety of a flexible dosage of venlafaxine XR in outpatients with GAD without associated MDD.DesignSix-month, randomized, double-blind, placebo-controlled, parallel-group trial conducted May 1996 to October 1997.SettingFourteen outpatient clinics and private psychiatric practices in the United States.ParticipantsA total of 251 outpatients aged 18 years or older who met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria for GAD, had sufficient symptoms to require treatment, and did not have coexisting MDD.InterventionsParticipants were randomly assigned to receive either placebo (n=127) or venlafaxine XR (75, 150, or 225 mg/d, as required to control symptoms; n=124) for 28 weeks.Main Outcome MeasuresChanges from baseline in the Hamilton Rating Scale for Anxiety (HAM-A) total score, the HAM-A psychic anxiety factor score, and the Clinical Global Impressions (CGI) scale Severity of Illness and Global Improvement scores, compared by intervention group.ResultsDuring weeks 6 through 28, response rates in the venlafaxine XR group were 69% or higher compared with rates of 42% to 46% in the placebo group (P<.001). By an evaluable-patient analysis, venlafaxine XR compared with placebo significantly improved anxiety scores from week 1 or 2 through week 28 on all primary efficacy measures, including the HAM-A total (P<.001), the HAM-A psychic anxiety factor (P<.001), and the CGI scale scores (P<.001). Adjusted mean changes from baseline to week 28 using last-observation-carried-forward methods were for HAM-A, venlafaxine XR −13.4, placebo −8.7 (P<.001); for HAM-A psychic anxiety score, venlafaxine XR −7.4, placebo −4.2 (P<.001); and for CGI-Improvement, venlafaxine XR 2.2, placebo 3.0 (P<.001). The most common treatment-emergent adverse event was nausea, followed by somnolence and dry mouth.ConclusionsThis study is the first placebo-controlled demonstration of the long-term efficacy of any drug class in treating outpatients with DSM-IV–diagnosed GAD. Venlafaxine XR is an effective, rapidly acting, safe, once-daily agent for both the short- and long-term treatment of anxiety and may provide an important alternative to currently available anxiolytics.