title: Quantitative assay of lorazepam and its metabolite glucuronide by reverse-phase liquid chromatography-tandem mass spectrometry in human plasma and urine samples.
abstract: A LC/MS/MS method for the quantitative determination of lorazepam in human plasma and urine samples was developed and validated. The enantioselective assay allowed to separate the enantiomers and to verify the stereochemical instability of lorazepam. The linearity assessed for lorazepam unchanged was 0.2-20 ng of each enantiomer/ml plasma and 0.2-15 ng of each enantiomer/ml urine. The linearity assessed for total lorazepam (after enzymatic hydrolysis) was 1-30 ng of each enantiomer/ml plasma and 10-150 ng of each enantiomer/ml urine. The coefficients of variation obtained for the intra- and interassay precision were less than 15%. The method was applied to the investigation of the kinetic disposition and metabolism of racemic lorazepam administered as a single oral dose of 2 mg to a parturient. The occurrence of racemization required the calculation of the pharmacokinetic parameters as enantiomeric mixtures of lorazepam (t(1/2a) 3.5h; K(a) 0.198 ngh(-1); t(1/2) 11.5h; beta 0.060 h(-1); AUC(0-infinity) 192.1ngh/ml; CLt/f 2.41ml/minkg; Vd/f 173.5l; Fel 0.41%, and Cl(R) 0.0099 ml/minkg) and its metabolite lorazepam-glucuronide (t(1/2f) 1.2h; K(f) 0.578 h(-1); t(1/2) 16.6h; beta 0.042 h(-1); AUC(0-infinity) 207.6 ngh/ml; Fel 51.80%, and Cl(R) 98.32 ml/minkg). However, the determined confidence limits make the method suitable for application to clinical pharmacokinetic studies, even if the quantification of both the enantiomers is required.
authors.affiliation: Faculdade de Ciências Farmacêuticas de Ribeirão Preto, USP, Universidade de São Paulo, Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Avenida do Café s/n, Campus da USP, 14040-903 Ribeirão Preto, Brazil.
authors.forename: Olga
authors.initials: O
authors.lastname: Papini
authors.forename: Carlo
authors.initials: C
authors.lastname: Bertucci
authors.forename: Sergio Pereira
authors.initials: SP
authors.lastname: da         Cunha
authors.forename: Neife Aparecida Guinaim
authors.initials: NA
authors.lastname: Dos       Santos
authors.forename: Vera Lucia
authors.initials: VL
authors.lastname: Lanchote
mesh_terms: D000097:Acetonitriles; D014151:Anti-Anxiety Agents / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D002853:Chromatography, Liquid / Q000379:methods*; D004355:Drug Stability; D005260:Female; D006801:Humans; D008140:Lorazepam / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics / Q000652:urine; D036801:Parturition / Q000378:metabolism; D011247:Pregnancy; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000097:Acetonitriles; D014151:Anti-Anxiety Agents; D008140:Lorazepam; C031290:lorazepam glucuronide; C032159:acetonitrile