title: Identifying Metabolites of Meclonazepam by High-Resolution Mass Spectrometry Using Human Liver Microsomes, Hepatocytes, a Mouse Model, and Authentic Urine Samples.
abstract: Meclonazepam is a benzodiazepine patented in 1977 to treat parasitic worms, which recently appeared as a designer benzodiazepine and drug of abuse. The aim of this study was to identify metabolites suitable as biomarkers of drug intake in urine using high-resolution mass spectrometry, authentic urine samples, and different model systems including human liver microsomes, cryopreserved hepatocytes, and a mice model. The main metabolites of meclonazepam found in human urine were amino-meclonazepam and acetamido-meclonazepam; also, minor peaks for meclonazepam were observed in three of four urine samples. These observations are consistent with meclonazepam having a metabolism similar to that of other nitro containing benzodiazepines such as clonazepam, flunitrazepam, and nitrazepam. Both metabolites were produced by the hepatocytes and in the mice model, but the human liver microsomes were only capable of producing minor amounts of the amino metabolite. However, under nitrogen, the amount of amino-meclonazepam produced increased 140 times. This study comprehensively elucidated meclonazepam metabolism and also illustrates that careful selection of in vitro model systems for drug metabolism is needed, always taking into account the expected metabolism of the tested drug.
authors.affiliation: Clinical Pharmacology, Division of Drug Research, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden. svante.vikingsson@liu.se.|Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden. svante.vikingsson@liu.se.
authors.forename: Svante
authors.identifier: 0000-0001-5977-3049
authors.initials: S
authors.lastname: Vikingsson
authors.affiliation: Clinical Pharmacology, Division of Drug Research, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.|Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.
authors.forename: Ariane
authors.initials: A
authors.lastname: Wohlfarth
authors.affiliation: Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.
authors.forename: Mikael
authors.initials: M
authors.lastname: Andersson
authors.affiliation: Clinical Pharmacology, Division of Drug Research, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.|Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.
authors.forename: Henrik
authors.initials: H
authors.lastname: Gréen
authors.affiliation: Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.
authors.forename: Markus
authors.initials: M
authors.lastname: Roman
authors.affiliation: Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.|Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Josefsson
authors.affiliation: Clinical Pharmacology, Division of Drug Research, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.|Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.
authors.forename: Fredrik C
authors.initials: FC
authors.lastname: Kugelberg
authors.affiliation: Clinical Pharmacology, Division of Drug Research, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden.|Department of Forensic Genetics and Forensic Toxicology, National Board of Forensic Medicine, Linköping, Sweden.
authors.forename: Robert
authors.initials: R
authors.lastname: Kronstrand
mesh_terms: D000818:Animals; D001570:Benzodiazepinones / Q000652:urine*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D013287:Illicit Drugs / Q000652:urine; D008297:Male; D008810:Mice, Inbred C57BL; D008862:Microsomes, Liver / Q000378:metabolism; D012556:Schistosomicides / Q000652:urine*; D002998:Clonazepam / Q000031:analogs & derivatives
chemical_list: D001570:Benzodiazepinones; D013287:Illicit Drugs; D012556:Schistosomicides; C020602:meclonazepam; D002998:Clonazepam
keywords: LC-MS/MS; benzodiazepine; in vitro metabolism; new psychoactive substance; toxicokinetics