Impact of gastrointestinal symptom severity on response to venlafaxine extended-release in patients with generalized anxiety disorder

Background: This retrospective analysis evaluated the prevalence and severity of pretreatment gastrointestinal (GI) symptoms in patients with generalized anxiety disorder (GAD), the impact of these GI symptoms on the efficacy and tolerability of venlafaxine extended-release (XR), and the effect of treatment on prestudy GI symptoms. Method: Data from 1932 nondepressed GAD patients were pooled from 5 randomized, double-blind, placebo-controlled studies of venlafaxine XR clinically conducted between May 1995 and December 1997. The GI symptom severity at baseline was estimated from item I I on the Hamilton Rating Scale for Anxiety (HAM-A). Patients with a GI symptom severity score less than or equal to 2 (moderate or less) and those with a GI symptom severity score > 2 (severe/very severe) were compared for baseline characteristics and short-term (8-week) and long-term (24-week) outcomes. Results: At baseline, for all randomized patients with a HAM-A item I I score, GI symptoms were rated moderate or lower in 82.8% of patients (GI-low) and severe/very severe in 17.2% (GI-high). The GI-high subgroup was statistically significantly (p < .05) younger, had a longer duration of GAD, and had higher mean HAM-A total scores than the GI-low subgroup. Compared with placebo, venlafaxine XR significantly reduced HAM-A total and psychic anxiety factor scores, regardless of baseline GI symptom severity. The incidence of adverse events, particularly nausea, was higher for the GI-high versus GI-low subgroup. Conclusion: Baseline severity of GI symptoms correlated with overall severity of GAD but had no impact on treatment outcome with venlafaxine XR. These data do not support the hypothesis that high baseline GI symptom severity has a negative effect on treatment with venlfaxine XR in GAD patients.