A non-inferiority comparison of duloxetine and venlafaxine in the treatment of adult patients with generalized anxiety disorder

Abstract

The present study is a non-inferiority comparison of duloxetine 60— 120 mg/day and venlafaxine extended-release (XR) 75—225 mg/day for the treatment of adults with generalized anxiety disorder (GAD). The non-inferiority test was a prespecified plan to pool data from two nearly identical 10-week, multicentre, randomized, placebo-controlled, double-blind studies of duloxetine 60-120 mg/day and venlafaxine 75—225 mg/ day for the treatment of GAD. An independent expert consensus panel provided six statistical and clinical criteria for determining non-inferiority between treatments. Response was defined as ≥50% reduction in Hamilton Anxiety Rating Scale (HAMA) total score. In the pooled sample, patients were randomly assigned to duloxetine ( n = 320), venlafaxine XR ( n = 333) or placebo ( n = 331). For the non-inferiority analysis, the per-protocol patients who were treated with duloxetine ( n = 239) or venlafaxine XR ( n = 262) improved significantly more (mean HAMA reductions were −15.4 and −15.2, respectively) than placebo-treated patients ( n = 267; −11.6, P ≤ 0.001, both comparisons). Response rates were 56%, 58% and 40%, respectively. Discontinuation rate because of AEs was significantly higher for duloxetine (13.4%, P ≤ 0.001) and venlafaxine XR (11.4%, P ≤ 0.01) groups compared with placebo (5.4%). Duloxetine 60—120 mg/day met all statistical and clinical criteria for non-inferiority and exhibited a similar tolerability profile compared with venlafaxine XR 75—225 mg/day for the treatment of adults with GAD.