Efficacy of low and higher dose extended-release venlafaxine in generalized social anxiety disorder: a 6-month randomized controlled trial

Rationale There is a need for new pharmacological treatments for generalized social anxiety disorder (GSAD), which is a common, often disabling condition.Objective To compare the efficacy and safety over 6 months duration of two dose ranges of venlafaxine extended-release (ER) with placebo in patients with GSAD.Method Twenty-eight-week, double-blind, multi-center study in 386 adult outpatients with DSM-IV GSAD. Patients were randomized to placebo, venlafaxine ER fixed low dose (75 mg/day), or venlafaxine ER flexible higher dose (150–225 mg/day). Primary efficacy variable was change on the Liebowitz Social Anxiety Scale (LSAS). Secondary efficacy variables included, among others, the proportion of responders on the CGI Global Improvement Item (score 1 or 2), and the proportion of remitters (defined as an LSAS score of 30).Results Improvement on the LSAS was greater with venlafaxine ER (at 75 mg/day or 150–225 mg/day) than placebo, and was sustained throughout the 6-month trial. Of patients receiving venlafaxine ER (at any dose), 58% responded to treatment compared to 33% of those receiving placebo (P<0.001); corresponding remission rates were 31% and 16% (P<0.01). There were no differences in outcome according to venlafaxine ER dosage.Conclusions Venlafaxine ER was effective in the treatment of GSAD. The comparable efficacy at low and higher doses may indicate that norepinephrine reuptake blockade does not contribute to therapeutic effect in GSAD. This hypothesis should be tested using agents with specific actions on norepinephrine reuptake blockade.