title: The influences of CYP2D6 genotypes and drug interactions on the pharmacokinetics of venlafaxine: exploring predictive biomarkers for treatment outcomes.
abstract: BACKGROUND
  Two biomarkers: concentration ratio of O-desmethylvenlafaxine/venlafaxine and concentration sum of venlafaxine + O-desmethylvenlafaxine were adopted to indicate venlafaxine responses, but neither is validated.
  
  
  OBJECTIVE
  To evaluate the ability of two biomarkers in reflecting venlafaxine pharmacokinetic variations, and to further examine their relationship with venlafaxine treatment outcomes.
  
  
  METHODS
  Two well-defined influencing factors: CYP2D6 genotypes and drug interactions were enriched into a three-period crossover study to produce venlafaxine pharmacokinetic variations: In each period, healthy CYP2D6 extensive metabolizers (EM group; n = 12) and CYP2D6*10/*10 intermediate metabolizers (IM group; n = 12) were pretreated with clarithromycin (CYP3A4 inhibitor), or nothing (control), or clarithromycin + paroxetine (CYP3A4 + CYP2D6 inhibitors), before administration of a single-dose of 75 mg venlafaxine. Both biomarkers were evaluated (1) for their relationship with the influencing factors in healthy volunteers and (2) for their relationships with the venlafaxine responses/adverse events reported in two patient studies.
  
  
  RESULTS
  Significant venlafaxine pharmacokinetic variations were observed between the EM and IM groups (geometric mean ratio [95 % CI] of area under the curve, 3.0 [1.8-5.1] in the control period), and between the control and clarithromycin + paroxetine periods (4.1 [3.5-4.7] and 2.0 [1.7-2.4] in the EM and IM group, respectively). O-Desmethylvenlafaxine/venlafaxine was superior to venlafaxine + O-desmethylvenlafaxine to reflect the influencing factors. In the patient studies, O-desmethylvenlafaxine/venlafaxine > 4 showed high precision in predicting venlafaxine responders/partial-responders (92 %) and patients without venlafaxine-related adverse events (88 %); the O-desmethylvenlafaxine/venlafaxine < 4 and venlafaxine + O-desmethylvenlafaxine > 400 ng/ml combination showed higher precision (100 %) than O-desmethylvenlafaxine/venlafaxine < 4 alone (65 %) in predicting venlafaxine non-responders.
  
  
  CONCLUSIONS
  We propose using O-desmethylvenlafaxine/venlafaxine for CYP2D6 phenotyping, and O-desmethylvenlafaxine/venlafaxine with venlafaxine + O-desmethylvenlafaxine for predicting venlafaxine treatment outcomes in future prospective studies.
authors.affiliation: Clinical Research Division, Toxicological Evaluation and Research Department, National Institute of Food and Drug Safety Evaluation, Complex, Osong, Chungcheongbuk-do, 363-700, Republic of Korea.
authors.forename: Fen
authors.initials: F
authors.lastname: Jiang
authors.forename: Hae-Deun
authors.initials: HD
authors.lastname: Kim
authors.forename: Han-Sung
authors.initials: HS
authors.lastname: Na
authors.forename: Seok-Yong
authors.initials: SY
authors.lastname: Lee
authors.forename: Doo-Won
authors.initials: DW
authors.lastname: Seo
authors.forename: Jong-Yeol
authors.initials: JY
authors.lastname: Choi
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Ha
authors.forename: Hee-Jung
authors.initials: HJ
authors.lastname: Shin
authors.forename: Young-Hoon
authors.initials: YH
authors.lastname: Kim
authors.forename: Myeon-Woo
authors.initials: MW
authors.lastname: Chung
mesh_terms: D000328:Adult; D018687:Antidepressive Agents, Second-Generation / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D017291:Clarithromycin / Q000494:pharmacology; D018592:Cross-Over Studies; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D000069468:Desvenlafaxine Succinate / Q000493:pharmacokinetics; D004347:Drug Interactions; D005260:Female; D005819:Genetic Markers / Q000235:genetics*; D005838:Genotype; D006801:Humans; D008297:Male; D008657:Metabolic Clearance Rate / Q000187:drug effects / Q000235:genetics; D017374:Paroxetine / Q000494:pharmacology; D010641:Phenotype; D011292:Premedication; D011446:Prospective Studies; D016896:Treatment Outcome; D000069470:Venlafaxine Hydrochloride / Q000493:pharmacokinetics* / Q000627:therapeutic use*; D055815:Young Adult
chemical_list: D018687:Antidepressive Agents, Second-Generation; D005819:Genetic Markers; D017374:Paroxetine; D000069470:Venlafaxine Hydrochloride; D019389:Cytochrome P-450 CYP2D6; D017291:Clarithromycin; D000069468:Desvenlafaxine Succinate