title: Metabolites of lorazepam: Relevance of past findings to present day use of LC-MS/MS in analytical toxicology.
abstract: The advent of liquid chromatography-tandem mass spectrometry (LC-MS/MS), with the sensitivity it confers, permits the analysis of both phase I and II drug metabolites that in the past would have been difficult to target using other techniques. These metabolites may have relevance to current analytical toxicology employing LC-MS/MS, and lorazepam was chosen as a model drug for investigation, as only the parent compound has been targeted for screening purposes. Following lorazepam administration (2 mg, p.o.) to 6 volunteers, metabolites were identified in urine by electrospray ionization LC-MS/MS, aided by the use of deuterated analogues generated by microsomal incubation for use as internal chromatographic and mass spectrometric markers. Metabolites present were lorazepam glucuronide, a quinazolinone, a quinazoline carboxylic acid, and two hydroxylorazepam isomers, one of which is novel, having the hydroxyl group located on the fused chlorobenzene ring. The quinazolinone, and particularly the quinazoline carboxylic acid metabolite, provided longer detection windows than lorazepam in urine extracts not subjected to enzymatic hydrolysis, a finding that is highly relevant to toxicology laboratories that omit hydrolysis in order to rapidly reduce the time spent on gas chromatography-mass spectrometry (GC-MS) analysis. With hydrolysis, the longest windows of detection were achieved by monitoring lorazepam, supporting the targeting of the aglycone with free drug for those incorporating hydrolysis in their analytical toxicology procedures.
authors.affiliation: Department of Forensic Science & Drug Monitoring, King's College London, 150 Stamford Street, London SE1 9NH, UK.
authors.forename: Sophie C
authors.initials: SC
authors.lastname: Turfus
authors.forename: Robin A
authors.initials: RA
authors.lastname: Braithwaite
authors.forename: David A
authors.initials: DA
authors.lastname: Cowan
authors.forename: Mark C
authors.initials: MC
authors.lastname: Parkin
authors.forename: Norman W
authors.initials: NW
authors.lastname: Smith
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Kicman
mesh_terms: D014151:Anti-Anxiety Agents / Q000378:metabolism* / Q000633:toxicity / Q000652:urine*; D002853:Chromatography, Liquid / Q000379:methods; D005260:Female; D006801:Humans; D008140:Lorazepam / Q000378:metabolism* / Q000633:toxicity / Q000652:urine*; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D053719:Tandem Mass Spectrometry / Q000379:methods*; D016482:Urinalysis / Q000379:methods
chemical_list: D014151:Anti-Anxiety Agents; D008140:Lorazepam