title: Assessment of activity levels for CYP2D6*1, CYP2D6*2, and CYP2D6*41 genes by population pharmacokinetics of dextromethorphan.
abstract: The pharmacokinetics of dextromethorphan (DM) is markedly influenced by cytochrome P450 2D6 (CYP2D6) enzyme polymorphisms. The aim of this study was to quantify the effects of the CYP2D6*1, *2, and *41 variants on DM metabolism in vivo and to identify other sources of pharmacokinetic variability. Concentrations of DM and dextrorphan (DO) in plasma and urine were evaluated in 36 healthy Caucasian men. These volunteers participated in three clinical studies and received a single oral dose of 30 mg DM-HBr. Data were modeled simultaneously using the population pharmacokinetics NONMEM software. A five-compartment model adequately described the data. The activity levels of the alleles assessed differed significantly. The clearance attributable to an individual CYP2D6*1 copy was 2.5-fold higher as compared with CYP2D6*2 (5,010 vs. 2,020 l/h), whereas the metabolic activity of CYP2D6*41 was very low (85 l/h). Urinary pH was confirmed as a significant covariate for DM renal clearance. These results refine genotype-based predictions of pharmacokinetics for DM and presumably for other CYP2D6 substrates as well.
authors.affiliation: Department of Pharmacology, Clinical Pharmacology Unit, University Hospital, University of Cologne, Cologne, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Abduljalil
authors.forename: D
authors.initials: D
authors.lastname: Frank
authors.forename: A
authors.initials: A
authors.lastname: Gaedigk
authors.forename: T
authors.initials: T
authors.lastname: Klaassen
authors.forename: D
authors.initials: D
authors.lastname: Tomalik-Scharte
authors.forename: A
authors.initials: A
authors.lastname: Jetter
authors.forename: U
authors.initials: U
authors.lastname: Jaehde
authors.forename: J
authors.initials: J
authors.lastname: Kirchheiner
authors.forename: U
authors.initials: U
authors.lastname: Fuhr
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000996:Antitussive Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D001711:Biotransformation; D002986:Clinical Trials as Topic; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics* / Q000378:metabolism*; D003915:Dextromethorphan / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D003917:Dextrorphan / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010641:Phenotype; D011110:Polymorphism, Genetic; D044465:White People / Q000235:genetics; D055815:Young Adult
chemical_list: D000996:Antitussive Agents; D003917:Dextrorphan; D003915:Dextromethorphan; D019389:Cytochrome P-450 CYP2D6