The Use of the 5-HT₃ Receptor Antagonist Tropisetron in Trigger Point Therapy: A Pilot Study

Abstract

Objectives: Local treatment of tendinopathies showed that the serotonin [5-HT₃] receptor antagonist tropisetron evidently has an analgesic and anti-inflammatory effect. We therefore investigated the question if this substance is also suitable for local treatment of trigger points.

Methods: Thirty-three patients with myofascial pain syndromes were enrolled in a double blind trial [blinded observer procedure]. A single dose of 5 mg 5-HT₃ receptor antagonist tropisetron or 10 ml 0.5 percent prilocaine solution, respectively, was injected into the corresponding trigger point.

Results: Nine of 17 patients receiving tropisetron and eight of 16 patients on prilocaine responded to treatment by showing a reduction in pain on the visual analog scale three hours after the injection. Seven days after injection, the visual analog scale-value in these cases decreased by 76.5 percent in the tropisetron group, whereas it was only by 14.8 percent in the prilocaine group. Compared to the prilocaine group, the patients that had received tropisetron showed significantly better results also in the follow-up eight weeks after injection.

Conclusion: Trigger point injection with the 5-HT₃ receptor antagonist tropisetron reduces pain in myofascial pain syndromes. The intense and long-term effect of the 5-HT₃ receptor antagonist tropisetron can be attributed to the substance's analgesic effect, and moreover, probably also to its anti-inflammatory action. Additional studies are needed for a more precise assessment.

KEYWORDS:

• Trigger point
• therapy
• 5-HT₃-receptor antagonist
• tropisetron
• myofascial pain syndrome