The 5-HT3 blockers in the treatment of the primary fibromyalgia syndrome: a 10-day open study with Tropisetron at a low dose.

A 10-day open trial with Tropisetron, the selective serotonin type 3 receptor antagonist, in a dose of 5 mg daily was undertaken in 19 patients with the primary fibromyalgia syndrome (FB). Before and after the therapy, pain was assessed using a visual analogue scale and a pain score. All the patients were asked about the presence and intensity of vegetative and functional symptoms. Moreover, the tenderness at the 24 typical tender points at baseline and at the end of the therapy was evaluated. A statistically significant improvement of all examined parameters was observed after the therapy. The efficacy of Tropisetron in a dose of 5 mg daily was comparable with the results obtained in a previously reported trial with a dose of 10 or 15 mg per day, but the frequency of gastric troubles decreased (21% vs. 60%). The hypothesis about the existence of two subgroups of patients with FB is also discussed.