Venlafaxine versus mirtazapine in the treatment of undifferentiated somatoform disorder: a 12-week prospective, open-label, randomized, parallel-group trial

OBJECTIVE: We set out to compare the efficacy and tolerability of mirtazapine versus venlafaxine in patients with undifferentiated somatoform disorder (USD) using the Patient Health Questionnaire-15 (PHQ-15). METHODS: This was a 12-week prospective, open-label, randomized, parallel-group trial. The trial consisted of six visits that included baseline and weeks 1, 2, 4, 8 and 12. The primary effectiveness measure was the mean change in PHQ-15 total score from baseline to the end of treatment. Secondary effectiveness measures included the mean changes in total scores on the Beck Depression Inventory (BDI) and the 12-item General Health Questionnaire (GHQ) from baseline to the end of treatment. Ninety-five subjects were randomized to either mirtazapine (n = 50) or venlafaxine (n = 45); 71 subjects completed the study (mirtazapine: n = 39/50 [78%]; venlafaxine: n = 32/45 [71%]). RESULTS: The mean total score on the PHQ-15 decreased by 34.7% (-8.4, p < 0.0001) from baseline to endpoint in the mirtazapine group and by 26.6% (-6.1, p < 0.0001) in the venlafaxine group. A marginally significant between-group difference was observed for the mean change in total score on the PHQ-15 from baseline to endpoint (F = 4.126, p = 0.046). The mean total scores on the GHQ-12 and BDI from baseline to endpoint decreased by -4.9 (29.4%, p < 0.0001) and -13.5 (55.9%, p < 0.0001), respectively, in the mirtazapine group, and by -4.3 (26.2%, p = 0.001) and -9.02 (46.0%, p < 0.0001), respectively, in the venlafaxine group. No between-group difference was observed for the mean changes in total scores on the secondary effectiveness measures from baseline to endpoint. Both treatments were well tolerated. CONCLUSION: Our findings suggest that both mirtazapine and venlafaxine may be effective and well tolerated in the treatment of patients with USD. Double-blind, placebo-controlled and/or head-to-head comparison studies are required to allow definite conclusions to be drawn.