Open trial of mirtazapine in patients with fibromyalgia

Some positive therapeutic effects in fibromyalgia syndrome (FS) were reported with both tricyclic and new antidepressant drugs as well as serotonergic agents (5HT2 and 5HT3 receptor blockers). In the present study, a novel antidepressant drug mirtazapine, 15-30 mg/day, has been used in 29 patients with FS in an open trial. Twenty-six patients completed the six-week study. Ten (38%) were considered responders on account of the reduction of > or =40% on pain, fatigue and sleep disturbances and remission of depressive symptoms at the end of study. Eighteen patients had at least moderate depression before mirtazapine treatment and 8 patients presented mild depressive symptoms. Reduction on main symptoms of FS after 6 weeks of mirtazapine treatment significantly correlated with the reduction in depression. However, the percentage of responders and patients with > or = 40% reduction on main symptoms of fibromyalgia was similar in high and low depression groups. The results obtained suggest that mirtazapine may be promising method of FS treatment. Further double-blind placebo-controlled studies are required to confirm these results.