Pharmacokinetics of selegiline, R‐methamphetamine, R‐amphetamine, and desmethylselegiline in oral fluid after a single oral administration of selegiline

Abstract

Background Chiral analysis is a crucial way to differentiate selegiline (SG) intake from drug abuse. Oral fluid (OF) has been successfully used as an alternative matrix for blood testing in several pharmacokinetic studies. Objective The aim of this study is to describe the pharmacokinetics of SG and its main metabolites in OF after a single oral administration of SG which is meaningful for results interpretation in forensic analysis. Methods Ten milligrams of SG were orally administered to 8 volunteers, and OF samples were collected for up to 96 hours by having participants spit into polypropylene tubes without stimulation. These samples were submitted to liquid–liquid extraction before analysis by liquid chromatography–tandem mass spectrometry operating in positive ion multiple‐reaction monitoring mode. Results and conclusions After oral administration, each analyte could be detected in OF specimens from all volunteers with an initial detection time of 0.50 hours. The Cmax values of SG, R‐MA, R‐AM and DM‐SG were 50.93–992.67 ng/mL, 29.78–653.64 ng/mL, 8.22–150.15 ng/mL, and 4.34–16.25 ng/mL, respectively, at 0.5 hours, 1–11 hours, 1.5–11 hours, and 0.5–6 hours post dose. The times when the compounds were last determined in OF were 5–24 hours for SG, 52–96 hours for R‐MA, 31–96 hours for R‐AM, and 13–31 hours for DM‐SG after oral administration. There is a period of time in OF in which only MA and AM are present without SG and DM‐SG after a single dose of SG. The pharmacokinetic data could provide supplementary interpretation for OF tests in forensic science and drug treatment programs.