Methods: Twenty-two patients with a median (IQR) age of 37 (27) years with clinical TMJ involvement of chronic polyarthritides and associated TMJ pain were included and allocated to two groups. The selective 5-HT3 receptor antagonist granisetron (3 mL, 1mg/mL) or 3 mL saline were injected into the upper TMJ compartment in a consecutive single-blind manner. TMJ resting pain and movement pain intensities were assessed with a visual analogue scale before injection and at certain time-points up to 60 min after the injections. Venous blood was collected for measurement of serum and plasma concentrations of 5-HT and inflammatory markers.
Results: TMJ resting pain and movement pain intensities decreased in both groups after injection. In the granisetron group, the serum concentration of 5-HT was negatively correlated to the TMJ pain intensity upon maximum mouth opening on the injection side 60 min after the granisetron injection relative to the preinjection pain intensity, i.e. the higher the serum concentration of 5-HT before injection the greater reduction of movement pain intensity.
Conclusion: This study indicates that the short-term analgesic effect on movement pain by the 5-HT3 receptor antagonist granisteron administered intraarticularly into the TMJ is enchanced by a high level of circulating 5-HT and thus is a specific effect in contrast to the effect on resting pain and the effects by saline.
This study was supported by grants from Karolinska Institutet, Sweden and by the Estonian Science Foundation Grant (4374).