Changes in plasma serotonin concentration and acceleration plethysmograms in patients with Raynaud's phenomenon after long-term treatment with a 5-HT2 receptor antagonist

High blood serotonin concentrations have been reported in patients with Raynaud's phenomenon and a relationship has been suggested. Because of the difficulty in evaluating Raynaud's phenomenon objectively, a possible correlation between blood serotonin concentrations and clinical findings has not yet been evaluated. We measured plasma serotonin concentrations and acceleration plethysmograms (APG) before and one year after administration of a serotonin receptor antagonist. Twenty-seven patients with either collagen disease or diseases associated with Raynaud's phenomenon were given a combined 5-HT2 and serotonin receptor antagonist, sarpogrelate hydrochloride. Plasma serotonin concentrations were determined before and after administration and the APG d/a value was measured as an index of peripheral hemodynamics. These values were compared with the clinical symptoms of the patients. After one year of treatment, the subjective symptoms improved in 59.3% of patients who has Raynaud's phenomenon. The pretreatment plasma serotonin concentrations of the study patients were significantly higher than those of the normal controls, but became significantly decreased following 5-HT2 administration. However, there was no clear-cut relationship with the clinical symptoms. The pre-treatment APG d/a value of the patients was significantly lower than that of the normal controls, although there was no significant difference after administration when analyzed as an entire group or in a subset of patients whose symptoms did not subjectively improve or worsened after one year of treatment. In the subset in whom the subjective symptoms improved, however, the value significantly increased following administration, suggesting an improvement in peripheral hemodynamics. These results suggest the possibility that APG can be used as an objective index of peripheral hemodynamics.