Treatment of chronic fatigue syndrome with 5-HT3 receptor antagonists - preliminary results

Objective: The serotonin system presumably is involved in the pathogenesis of chronic fatigue syndrome (CFS). Results from a few studies led to the hy pothesis of a "postsynaptic hyperresponsiveness'' in CFS. Therefore we inte nded to evaluate the efficacy of 5-HT3 receptor antagonists in the treatmen t of CFS. Patients and Methods: 2 patient groups (10 patients each; CFS according to the CDC classification criteria) received either oral tropisetron (5 mg onc e daily) or oral ondansetron (2 x 8 mg daily), open-labelled. Treatment dur ation was 15 days. Treatment response was evaluated by visual analog scales (VAS) for fatigue and capability. Results: 19 patients finished their respective study. In the tropisetron gr oup 6/9 (VAS fatigue) and 7/9 (VAS capability) patients documented benefit, 8/10 rsp. 8/10 patients in the ondansetron group. The score changes (VAS b efore and after treatment) in case of response were more pronounced in the tropisetron group. The frequency of concomitant symptoms did not differ sig nificantly in the treatment groups. The overall analysis of both studies sh owed a remarkable improvement (greater than or equal to 35%) of approximate ly one third of the patients in both VAS. Treatment was well tolerated. Conclusion: Our preliminary results encourage to perform placebo-controlled , double-blind studies to further evaluate the efficacy of 5-HT3 receptor a ntagonists in the treatment of CFS.