title: Effects of polymorphisms in CYP2D6, CYP2C9, and CYP2C19 on trimipramine pharmacokinetics.
abstract: Little is known about the impact of cytochrome P450 polymorphisms on the metabolism of trimipramine, which is still widely used as antidepressant due to its positive effect on sleep patterns. A single oral dose of 75 mg trimipramine was given to 42 healthy volunteers selected according to their CYP2D6, CYP2C19, and CYP2C9 genotypes. The reference group included 8 subjects with homozygous active wild-type genotypes of all 3 enzymes (EM). This group was compared with 7 intermediate (IM) with 1 and 7 poor metabolizers (PM) with zero active alleles of CYP2D6 and CYP2C19, respectively, and with 4 subjects with the genotype CYP2C9*3/*3. Pharmacokinetics of trimipramine and its demethylated metabolite strongly depended on the CYP2D6 genotype. Median oral clearance of trimipramine was 276 L/h (range 180-444) in the reference group but only 36 L/h (range 24-48) in CYP2D6 PMs (P < 0.001). These differences could only be explained by an effect of CYP genotypes on both parameters, systemic clearance and bioavailability, the latter being at least 3-fold higher in CYP2D6 PMs than in the reference group. The desmethyltrimipramine area under the concentration-time curve was 40-fold greater in CYP2D6 PMs than in the reference group (1.7 vs. 0.04 mg/L x h in EMs), but below the quantification limit in most carriers of deficiencies of CYP2C19 or CYP2C9. This indicates that both CYP2C enzymes contribute to the demethylation of desmethyltrimipramine and CYP2D6 to further metabolism.
authors.affiliation: Institute of Clinical Pharmacology, University Medical Center Charité, Humboldt University of Berlin, Berlin, Germany. julia.kirchheiner@charite.de
authors.forename: Julia
authors.initials: J
authors.lastname: Kirchheiner
authors.forename: Gunnar
authors.initials: G
authors.lastname: Müller
authors.forename: Ingolf
authors.initials: I
authors.lastname: Meineke
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Wernecke
authors.forename: Ivar
authors.initials: I
authors.lastname: Roots
authors.forename: Jürgen
authors.initials: J
authors.lastname: Brockmöller
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D016001:Confidence Intervals; D065731:Cytochrome P-450 CYP2C19; D065729:Cytochrome P-450 CYP2C9; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects / Q000235:genetics; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000235:genetics*; D011110:Polymorphism, Genetic; D018709:Statistics, Nonparametric; D014299:Trimipramine / Q000493:pharmacokinetics*
chemical_list: D014299:Trimipramine; D006899:Mixed Function Oxygenases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D019389:Cytochrome P-450 CYP2D6