Neuroendocrine response to fenfluramine in patients with idiopathic pain syndromes

In chronic pain patients, a long series of studies indicate disturbances in the serotoninergic systems as one important pathogenetic factor. One way of studying the function of the serotoninergic system would be to study the neuroendocrine responses to serotoninergic agonists. In the present study, twelve healthy volunteers and 17 chronic pain patients were given fenfluramine, 60 mg, at 8 a.m. Serum Cortisol and serum prolactin were measured at 8 a.m., 9 a.m., 10 a.m., 11 a.m. and at noon. The symptomatology was at the same time determined using visual analogue scales (VAS). Fenfluramine, a drug that releases intraneuronal serotonin and blocks the reuptake of serotonin, seems to have a stimulatory effect on the release of Cortisol and prolactin. As concerns serum Cortisol, the chronic pain patients had significantly lower values at 8 a.m. than the healthy volunteers. From 8 a.m. to 10 a.m. the values increased in the chronic pain patients but decreased in the healthy volunteers. The difference between the changes was statistically significant. The prolactin response was not significantly different between healthy volunteers and chronic pain patients. No pronounced changes were noted in the symptomatology of the chronic pain patients while fenfluramine produced concentration difficulties and memory disturbances in the healthy volunteers. The results provide some support for the hypothesis that the serotoninergic transmission is disturbed in patients with chronic pain syndromes. Chronic pain, Cortisol, Fenfluramine, Prolactin, Serotonin.