Effects of antidepressant mirtazapine on fibromyalgia symptoms

Fibromyalgia syndrome (FS) is a form of non-articular rheumatism. The main criteria are the widespread musculoskeletal pain and tender points at multiple characteristic sites which are associated with several vegetative and functional symptoms. Depression is the most frequent psychiatric concomitant of FS. Etiology is unknown, connection between disturbances of serotonin metabolism and pathogenesis is postulated. Pharmacological therapy with analgetic and nonsteroidal antiinflammatory drugs is not very effective. Positive effects were reported in some patients treated with antidepressant drugs, especially serotonergic agents.

In the study a novel antidepressant drug mirtazapine was used characterized by selective blockade of 5-HT2 and 5-HT3 receptors. In an open trial participated 29 patients with FS, who met 1990 ACR criteria for fibromyalgia. All were treated with mirtazapine for 6 weeks. Intensity of pain, sleep disturbances, fatigue and other symptoms were measured using visuale analogue scale, severity of depression was evaluated with HDRS and BDI.

An open trial completed 26 patients, the majority of them experienced a clinical improvement at the end of the study as a consequence of > or = 40% reduced intensity of fibromyalgia symptoms as well as reduced severity of depression. The significant correlation between reduction in depression after 6 weeks of mirtazapine treatment with the reduction on all four main symptoms of FS suggests a common pathophysiology of depression and symptoms of fibromyalgia. The data thus far obtained indicate the blockade of 5-HT2 and 5-HT3 receptors with mirtazapine as an effective and promising method in FS.

Further double-blind placebo-controlled study are required to confirm our results.