Fenfluramine and Idiopathic Pain: A Serotonergic Study in Non-Psychiatric Patients with Functional Gastrointestinal Disorder

Background: We investigated prolactin and cortisol response to fenfluramine in non-psychiatric patients with chronic functional gastrointestinal disorder (FGD). Methods: Sixty milligrams fenfluramine was given orally to 55 subjects without any DSM-III axis-1 psychopathology and 29 healthy control subjects matched for sex and age. Serum cortisol and prolactin levels were analysed at base line and after 120, 180, and 240 min. Results: Fenfluramine challenge induced an increase in mean prolactin and cortisol serum values in both patients and controls. Female patients showed lower base-line values of prolactin and higher delta values of cortisol than controls. Male patients and controls showed very uniform values for all variables. Length of illness history influenced delta cortisol values in both sexes. Conclusions: The cortisol and prolactin responses to fenfluramine suggest a psychobiologic gender difference with a possible stress-induced central serotonergic dysfunction in female patients but not in male patients. The close relationship between length of illness and delta cortisol may also suggest an increased state of distress in females with chronic functional gastrointestinal disorder.