title: LC-MS/MS analysis of dextromethorphan metabolism in human saliva and urine to determine CYP2D6 phenotype and individual variability in N-demethylation and glucuronidation.
abstract: In order to establish a fast screening method for the determination of the CYP2D6 metabolic phenotype a sensitive LC-MS/MS assay to quantify dextromethorphan (DEX) and its O-demethylated metabolite dextrorphan (DOR) in human saliva was developed with limits of quantitation of 1 pmol/ml. Saliva was provided by 170 medical students 2h after oral ingestion of 30 mg (81 micromol) dextromethorphan hydrobromide. Individual ratios of the concentrations DEX/DOR (metabolic ratio, MR(DEX/DOR)) varied more than 25,000-fold (0.03-780). Two groups comprising 156 'Extensive' and 14 'Poor Metabolizers' were clearly distinguished. For the investigation of individual differences in N-demethylation and glucuronidation, four additional metabolites of DEX, 3-methoxymorphinan (MOM), 3-hydroxymorphinan (HOM), and the two O-glucuronides (DORGlu and HOMGlu) were measured by LC-MS/MS analysis of 6-h urine of 24 volunteers. The N-demethylation reactions DEX-to-MOM and DOR-to-HOM defined by the respective MR were significantly correlated. The same holds for the glucuronidation pathways (MR(DOR/DORGlu) versus MR(HOM/HOMGlu)). The three poor CYP2D6 metabolizers excreted relatively high amounts of the parent compound DEX (up to 7 micromol), but only low amounts of glucuronides (DORGlu: 0.4-1.0 micromol; HOMGlu: 0.2-0.7 micromol). For the 21 'Extensive Metabolizers', the two glucuronides were the most abundant, with relatively little interindividual variation (DORGlu: 10-44 micromol; HOMGlu: 5-17 micromol). For the excretion of the glucuronides, two normal distributions provided the best fit, indicating that the determination of the glucuronides alone could allow assignment of the CYP2D6 metabolic phenotype.
authors.affiliation: Department of Toxicology, University of Würzburg, Versbacher Str. 9, D-97078 Würzburg, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Lutz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Völkel
authors.forename: Roman W
authors.initials: RW
authors.lastname: Lutz
authors.forename: Werner K
authors.initials: WK
authors.lastname: Lutz
mesh_terms: D002853:Chromatography, Liquid / Q000379:methods*; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D003915:Dextromethorphan / Q000378:metabolism* / Q000652:urine; D020719:Glucuronides / Q000378:metabolism; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D008745:Methylation; D010641:Phenotype; D012463:Saliva / Q000378:metabolism*
chemical_list: D020719:Glucuronides; D003915:Dextromethorphan; D019389:Cytochrome P-450 CYP2D6