Open trial of mirtazapine in patients with fibromyalgia

Background: 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). Methods: 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. Results: Twenty-six patients completed the six-week study. Ten (38%) were considered responders on account of the reduction of greater than or equal to40% 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 40% reduction on main symptoms of fibromyalgia was similar in high and low depression groups. Conclusions: 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.