The aim of the study was to assess the influence of the 5HT3-receptor antagonist tropisetron on circulating catecholamines as biochemical markers of the activity of the sympathoadrenal system in fibromyalgia. Moreover, serum concentrations of serotonin, somatomedin C, oxytocin, calcitonin-gene-related-peptide, calcitonin and cholecystokinin were assayed as putative markers in pain-related disorders like primary fibromyalgia.
In 96 patients, who met the ACR classification criteria for fibromyalgia, and in 20 sex and age matched controls concentrations of dopamine, noradrenaline, adrenaline, serotonin and tropisetron were assayed in serum by HPLC with electrochemical detection. All other transmitters were determined by ELISA.
There was with the exception of tropisetron, calcitonin and dopamine, no correlation between doses of tropisetron 5, 10, 15 mg respectively and significant changes in circulating transmitters or other transmitters as putative biochemicals markers in primary fibromyalgia. Regarding the prediction of pain reduction to tropisetron, patients with elevated dopamine and/or reduced plasma 5-HT concentrations tended to show a higher response rate.
Despite these partly disappointing results another prospective pilot study with selected patients vs. age and sex matched controls, double blind and with comparison of other 5HT3-receptor antagonists e.g. dolasetron and granisetron e.g. after i.v. bolus injection is suggested. Still the data obtained in this preliminary paper provide some evidence regarding the present discussion on subgroups of patients with primary fibromyalgia.