title: Trimipramine pharmacokinetics after intravenous and oral administration in carriers of CYP2D6 genotypes predicting poor, extensive and ultrahigh activity.
abstract: OBJECTIVE
  The tricyclic antidepressant trimipramine is one of the drugs with the most pronounced differences in pharmacokinetics caused by the CYP2D6 genetic polymorphism. However, the effect of CYP2D6 genotype on steady state kinetics and on bioavailability has not been studied so far. In addition, we were interested in trimipramine pharmacokinetics in genetically defined ultra rapid metabolizers.
  
  
  METHODS
  We studied intravenous and multiple dose oral application of 50 mg trimipramine in five, seven, and three healthy volunteers with CYP2D6 genotypes predicting deficient, highly active and ultrarapid metabolism. The latter group included carriers of one wild-type and one duplication allele. Trimipramine and desmethyltrimipramine concentrations were measured by HPLC over a time interval of 72 h after intravenous and after one oral application.
  
  
  RESULTS
  Both bioavailability and systemic clearance significantly depended on CYP2D6 genotype with a linear gene dose relationship. Mean bioavailability was 44, 16 and 12% in carriers of zero, two and three active genes of CYP2D6, respectively, and the corresponding data for systemic clearance were 12.0, 24.2, and 30.3 l/h. Consequently, the mean total oral clearances were 27.3, 151, and 253 l/h in poor, extensive and ultrarapid metabolizers.
  
  
  CONCLUSIONS
  High bioavailability combined with low systemic clearance of trimipramine in poor metabolizers of CYP2D6 substrates results in a very high exposure to trimipramine with the risk of adverse drug reactions. On the other hand, the extremely high systemic and presystemic elimination may result in sub-therapeutic drug concentrations in carriers of CYP2D6 gene duplications with a high risk of poor therapeutic response.
authors.affiliation: Institute of Clinical Pharmacology, University Medical Center Charité, Humboldt University of Berlin, Berlin. julia.kirchheiner@charite.de
authors.forename: Julia
authors.initials: J
authors.lastname: Kirchheiner
authors.forename: Johanna
authors.initials: J
authors.lastname: Sasse
authors.forename: Ingolf
authors.initials: I
authors.lastname: Meineke
authors.forename: Ivar
authors.initials: I
authors.lastname: Roots
authors.forename: Jürgen
authors.initials: J
authors.lastname: Brockmöller
mesh_terms: D000284:Administration, Oral; D000929:Antidepressive Agents, Tricyclic / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D005838:Genotype; D006801:Humans; D007262:Infusions, Intravenous; D014299:Trimipramine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics*
chemical_list: D000929:Antidepressive Agents, Tricyclic; D014299:Trimipramine; D019389:Cytochrome P-450 CYP2D6; C040606:desmethyltrimipramine