Oral treatment of fibromyalgia with tropisetron given over 28 days: influence on functional and vegetative symptoms, psychometric parameters and pain

The 5-HT3 receptor antagonists are a novel therapy for patients suffering f rom fibromyalgia, although the optimal duration of treatment is still uncle ar. The objective of this phase II study was to evaluate whether prolonging treatment with tropisetron to 4 weeks is tolerable and correlated with an improved clinical benefit. Thirty female patients with fibromyalgia receive d oral tropisetron (5 mg) daily for 28 days in an open-label fashion. Treat ment resulted in significantly decreased pain as measured by visual analog scale (VAS), with a mean reduction of 59.7% and an absolute median change o f -25.0 from baseline to day 28 (p<0.0001). A similar, significant reductio n of 55.7% and absolute median change of -31.0 was observed in the painscor e (p<0.0001). The response rate with patients showing a greater than or equ al to 35% reduction in individual pain scores was 72.4% at day 28. The pres sure tolerance of tender-points was slightly increased at the end of the tr eatment period. In addition, significant improvements were observed in the State-Trait-Anxiety-Inventory (STAI), scales of von Zerssen (Bf-S) and Beck Depression Index (BDT). Functional symptoms were compared with the results from a 10-day, randomized, double-blind phase III study of tropisetron in 418 fibromyalgia patients. In both studies several functional symptoms such as sleep disturbances and dizziness improved significantly (p < 0.05). In the 28 days study, the number and extent of improvement in functional sympt oms was increased compared with the shorter trial. Tolerability and safety of tropisetron was good, and typically for 5-HT3-receptor antagonists, gast rointestinal symptoms and headache were the most frequently reported events . In conclusion, 28 days treatment of fibromyalgia patients with 5 mg tropi setron resulted in significant pain reduction, which was most pronounced af ter 10 days with a further reduction up to day 28. Psychometric tests showe d significant improvements in depression and anxiety state scores, while fu nctional symptoms improved with extended tropisetron treatment.