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Duloxetine Treatment Similar to Venlafaxine for Adults With GAD: Presented at ADAA

By Mike Fillon

SAVANNAH, Ga -- March 10, 2008 -- Duloxetine treatment has similar efficacy to venlafaxine for adults with generalised anxiety disorder (GAD), according to study results presented here at the Anxiety Disorders Association of America (ADAA) 28th Annual Conference.

Duloxetine is a selective serotonin-norepinephrine reuptake inhibitor while venlafaxine belongs to the serotonin-norepinephrine reuptake inhibitor class.

According to lead researcher Christer Allgulander, MD, Associate Professor, Karolinska Institutet, Stockholm, Sweden, establishing similar efficacy between two medications can provide guidance for treatment planning by allowing consideration of other patient care uses, such as adverse event profile, comorbidities, cost, access, and preference.

"Noninferiority trials are designed to show that a treatment is no worse than an already established treatment," said Dr. Allgulander in his presentation on March 7. "Given their complexity, they require careful consideration of statistical and clinical criteria."

According to ADAA, GAD is characterised by persistent, excessive, and unrealistic worry about everyday things, occurring on more days than not for at least 6 months. ADAA estimates that there are 6.8 million people with GAD, and women are twice as likely to be affected as men.

In their study, Dr. Allgulander and colleagues pooled data from two nearly identical 10-week, multicentre, randomised, double-blind studies that each compared duloxetine 60 to120 mg/day and venlafaxine XR 75 to 225 mg/day with placebo. Patients were male or female outpatients 18 years or older, diagnosed with GAD according to criteria in the Diagnostic and Statistical Manual of Mental Disorders Fourth Revision, Text Edition. The primary efficacy measure was the Hamilton Anxiety Rating Scale (HAM-A) total score.

Based on an expert consensus panel's recommendations, the noninferiority comparison involved six statistical and clinical criteria and the use of a per-protocol population, defined as patients who had at least 4 weeks of treatment, HAM-A ratings after 4 weeks, compliance with study drug, and no protocol violations.

In the pooled sample, patients were randomly assigned to receive duloxetine (n = 320), venlafaxine (n = 333), or placebo (n = 331).

The per-protocol patients treated with duloxetine (n = 239) or venlafaxine XR (n = 262) had significantly greater improvement in mean HAM-A reductions (-15.4 and -15.2, respectively) compared with placebo (-11.6, P <= .001, both comparisons). Intent-to-treat sample response rates were 56%, 58%, and 40% respectively.

Adverse-event-related discontinuation rates were significantly higher for the duloxetine (13.4%, P <= .001) and venlafaxine XR (11.4%, P <= .01) groups compared with the placebo group (5.4%).

The researchers concluded that duloxetine 60 to 120 mg/day met all statistical and clinical criteria for noninferiority and exhibited a similar tolerability profile compared with venlafaxine XR 75 to 225 mg/day for the treatment of adults with GAD.

"Both active medications had similar tolerability in treatment-emergent adverse event profiles and mean change in vital signals," said Dr. Allgulander. "As a result, duloxetine can be considered to be similar to venlafaxine XR treatment for efficacy and tolerability in adult patients with GAD."

Funding for this study was provided by Eli Lilly and Company and Boehringer Ingelheim GmbH.


[Presentation title: A Noninferiority Comparison of Duloxetine and Venlafaxine XR for the Treatment of Adult Patients With Generalized Anxiety Disorder. Abstract 18]

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