Fenfluramine and 5-hydroxytryptamine?. Part 1: Is fenfluramine or norfenfluramine involved in the decrease of brain 5-hydroxytryptamine.

Both fenfluramine and de-ethylated fenfluramine decrease the brain stores of 5-hydroxytryptamine (5-HT). As the fenfluramine metabolite is present in the brain of the rat after fenfluramine injection, it could be suggested that the depletion of brain 5-HT elicited by fenfluramine is mediated by its metabolite. Comparative studies on 5-HT lowering effects and drug brain levels, indicate a primary effect of fenfluramine, following by the rising involvement of the de-ethylated compound in the sustained effect.