D,L-fenfluramine challenge test: Experience in nonpatient sample

The plasma prolactin response to a single-dose fenfluramine challenge is increasingly utilized in psychiatric research as an indirect and noninvasive measure of central serotonergic activity. However, the influences of age, gender and body weight on prolactin response and characterization of physical and psychological symptoms evoked by fenfluramine remain poorly studied. In the current study, 83 nonpatient male and female volunteers, 25-60 years old, were administered a standardized fenfluramine challenge test (60 mg), Serial blood samples for plasma drug concentration and plasma prolactin concentration were obtained and side effects reported by participants were recorded Analyses revealed that both plasma drug concentration and prolactin response were correlated with weight-relative dose (r = 0.43 and r = 0.38, respectively; p < 0.001). No significant relationship was noted between prolactin response and either age or gender, Symptoms during fenfluramine challenge were reported by 90% of subjects, most commonly fatigue, headache, lightheadedness, and difficulty concentrating, Overall side effect severity was related to weight-relative dose (r = 0.26; p < 0.05) and prolactin response (r = 0.42; p < 0.001). We conclude that fenfluramine challenge results should be reported as change in plasma prolactin relative to dose, and that in nonpatient samples the test is associated with frequent side effects.