Increased plasma serotonin in complex regional pain syndrome type 1

BACKGROUND: In patients with complex regional pain syndrome type 1 (CRPS1), some improvement can be achieved by the administration of ketanserin, a 5-HT2A receptor antagonist. We measured plasma levels of serotonin (5-HT) during CRPS1 and correlated these levels with disease characteristics. METHODS: Plasma 5-HT was measured in 35 patients who had CRPS1 for 3 yr and compared with 35 age-matched healthy controls. RESULTS: The plasma 5-HT levels were 411 ± 263 nmol/L and 29 ± 18 nmol/L, respectively (P < 0.001). No correlations with disease characteristics were observed. CONCLUSIONS: The markedly elevated levels of plasma 5-HT in CRPS1 patients suggest a role for 5-HT during the course of this disease. However, because of the lack of correlations with distinct disease characteristics, 5-HT is probably one of a number of mediators in CRPS1.