Influence of tropisetron on the serum substance P levels in fibromyalgia patients.
BACKGROUND
Substance P is found at an elevated level in the cerebrospinal fluid of fibromyalgia (FM) patients. Treatment with tropisetron leads in a subgroup of FM patients to pain reduction. The question arises of whether the substance P level in the serum can be changed by tropisetron treatment.


METHODS
Twenty patients with FM diagnosed according to the ACR criteria were treated for 5 days with a 5 mg tropisetron intravenous (i.v.) bolus injection daily. Before the first injection, 3 h later, and before and 3 h after the last injection, the serum levels of substance P were determined. The determination of this substance was carried out by means of an immunoassay from Assay Design Biotrend, Cologne. To evaluate the success of the tropisetron treatment, patients made a global assessment as 'clearly better', 'better', 'unchanged', or 'poor'. Patients who answered 'clearly better' and 'better' were regarded as responders.


RESULTS
Of the 20 patients, ten reported a good or very good influence on their pain (responders). In these responders, the means of the serum substance P levels were elevated in comparison with the non-responders, though the difference was not significant. In responders, the 5-HT3 receptor antagonist tropisetron produced a significant decrease in the serum substance P levels, while this did not occur in the non-responders.


CONCLUSIONS
It is possible that the responders to tropisetron represent a subgroup of FM patients for whom substance P and 5-HT3 receptors play key roles in the development of the pain symptoms.
Stratz
T
T
Hochrhein Institute of Rehabilitation Research, Department of Clinical Research, Bad Säckingen, Germany.
Fiebich
B
B
Haus
U
U
Müller
W
W
D005260:Female; D005356:Fibromyalgia / Q000097:blood*; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D008875:Middle Aged; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists / Q000494:pharmacology*; D013373:Substance P / Q000097:blood*; D013997:Time Factors; D000077526:Tropisetron
D007211:Indoles; D058831:Serotonin 5-HT3 Receptor Antagonists; D012702:Serotonin Antagonists; D013373:Substance P; D000077526:Tropisetron