Excretion of 4-fluoroamphetamine and three metabolites in urine after controlled oral ingestion

Each year, synthetic drugs are occurring in high numbers in the illicit drug market. But data on their pharmacology and toxicology are scarcely available. Therefore, a pilot study was performed to evaluate excretion of 4-fluoroamphetamine (4FA) in humans and identify metabolites in urine.Twelve subjects ingested 100 mg and five 150 mg 4-FA in a bitter lemon drink. Urine samples were scheduled at baseline and 4 times during the following 12 h and analyzed by liquid chromatography-mass spectrometry (LC-MSMS).Concentrations of 4-FA were in the range of 0.7–38 mg/l which is in accordance with the data in previously reported cases. A marked decrease of creatinine excretion in the first two samples was noted. The creatinine normalized concentrations show a maximum 4 h after ingestion in accordance with serum pharmacokinetics. Three products of two metabolic pathways were identified in very low concentrations, two diastereomers of 4-fluorophenylpropanolamine and one ring hydroxylated 4-FA that was conjugated to a large extent. The concentration-time courses paralleled those of 4-FA.The study results show the range of 4-FA concentrations to be expected in urine after oral ingestion of typical dosages and show two pathways of 4-FA metabolism