Pattern of Symptom Improvement Following Treatment With Venlafaxine XR in Patients With Generalized Anxiety Disorder

Background: The efficacy of anxiolytic drugs in generalized anxiety disorder (GAD) is conventionally assessed by evaluating changes in the total score of psychometric scales such as the Hamilton Rating Scale for Anxiety (HAM-A). The purpose of this pooled analysis of data was to evaluate the efficacy of venlafaxine extended release (XR) on individual items of the HAM-A and the Brief Scale for Anxiety (BSA).

Method: Data were pooled from 5 studies of patients with GAD who were treated with either venlafaxine XR or placebo for 8 weeks (N = 2021) and up to 6 months (N = 767). Individual items of the HAM-A and the BSA were examined, and, using the mean changes from baseline to endpoint, an effect size for each item was calculated by dividing the difference between baseline and endpoint values for each item by the standard deviation of this difference. The effect sizes determined for the venlafaxine group were compared with those for the placebo group. Items from each scale that are concordant with the DSM-IV diagnostic criteria for GAD were selected for further examination, and the specific effect sizes of each item were expressed after controlling for placebo effects.

Results: The effect size of the majority of the 14 items of the HAM-A scale and the 10 items of the BSA scale associated with treatment with venlafaxine XR was greater than with placebo at both 8 weeks and 6 months. Furthermore, the effect sizes at 6 months were generally greater than at 8 weeks in venlafaxine XR-treated patients. Effect sizes associated with venlafaxine XR were greatest for the HAM-A items that were most closely related to diagnostic symptoms of GAD, namely anxious mood, tension, intellectual functioning, and behavior at interview at both 8 weeks and 6 months. Similarly, GAD-related BSA items of inner tension, worrying over trifles, hostile feelings, and muscular tension were associated with the greatest improvements with venlafaxine XR at both timepoints.

Conclusion: The HAM-A and BSA items that most closely corresponded to DSM-IV diagnostic criteria for GAD showed the largest improvement during treatment with venlafaxine XR. This indicates that the specific symptoms of GAD can be treated effectively with venlafaxine XR, both in the short and longer term.