Effectiveness of venlafaxine, extended release formulation, in the short-term and long-term treatment of generalized anxiety disorder:: Results of a survival analysis

A survival analysis of data from two placebo-controlled, randomized, long-term (6-month) studies was used to examine the effectiveness of venlafaxine, extended release (XR) formulation, in patients with generalized anxiety disorder (GAD). Patients in a placebo-controlled, flexible-dose study received 75 to 225 mg/day venlafaxine XR, while patients in a placebo-controlled, fixed-dose study received once-daily venlafaxine XR doses of 37.5 mg, 75 mg, or 150 mg. The survival analysis was based on the clinician's decision to discontinue treatment in a placebo-controlled study and incorporated data from all patients who were randomized. In each study, placebo-treated patients discontinued treatment due to lack of efficacy more frequently and earlier than those receiving venlafaxine XR (p < 0.001, log-rank test). A dose-response relationship was apparent, with the lowest rate of withdrawal seen at the highest venlafaxine XR dose. Survival curves for discontinuations due to adverse events did not differ significantly in either study. These results were consistent with the conventional intent-to-treat efficacy assessments of changes in anxiety severity, highlighting the superiority of venlafaxine XR over placebo in the long-term treatment of GAD. Overall, these results demonstrate the clinical effectiveness of venlafaxine XR in the short-term and long-term treatment of GAD.