Fenfluramine in man: hypophagia associated with diminished serotonin turnover

A double-blind trial of orally administered fenfluramine was conducted in 7 non-obese adults with various neurological disorders. Caloric intake and body weight fell significantly after 8 days of treatment although there was no definite change in appetite ratings. Average central turnover of serotonin, as estimated by the cerebrospinal fluid (CSF) accumulation of 5-hydroxyindoleacetic acid (5-HIAA) during probenecid loading, decreased by 66%. No significant change in homovanillic acid, the major dopamine product, was apparent. The results support the contention that the effect of fenfluramine on human dietary intake may be mediated by alterations in serotonergic rather than dopaminergic mechanisms.