Pharmacokinetics of fenfluramine enantiomers in man

The pharmacokinetics of fenfluramine enantiomers were studied in normal volunteers following the administration of single of multiple doses of racemic fenfluramine hydrochloride. Plasma concentrations and half-lives were similar for both enantiomers after single 40 mg of 60 mg doses. However following chronic administration (2 x 40 mg for 10 days), significant differences were observed between the kinetic parameters of the two enantiomers, the l-form of fenfluramine and norfenfluramine accumulating in plasms more than the d-forms.