title: Impact of cytochrome P450 2C19 polymorphisms on citalopram/escitalopram exposure: a systematic review and meta-analysis.
abstract: BACKGROUND
  Citalopram and escitalopram, selective serotonin reuptake inhibitors, are primarily metabolized by cytochrome P450 (CYP) 2C19, which is a highly polymorphic enzyme known to cause inter-individual differences in pharmacokinetics. However, the impact of CYP2C19 polymorphisms on citalopram or escitalopram exposure has yet to be fully clarified, especially with regard to the quantitative impact of the CYP2C19*17 allele.
  
  
  OBJECTIVE
  The objective of this study was to quantify the effect of functional CYP2C19 allele variants on citalopram/escitalopram exposure.
  
  
  METHODS
  We performed a systematic review and meta-analysis with a structured search algorithm and eligibility criteria for including related studies, calculating the change of citalopram or escitalopram exposure associated with CYP2C19*2, *3, and *17 as compared with CYP2C19*1 using fixed-effect and random-effects models. Assessment of publication bias was performed by means of funnel plots and sensitivity analysis using meta-regressions. The pre-defined review protocol was registered at the PROSPERO international prospective register of systematic reviews, registration number CRD42013004106.
  
  
  RESULTS
  Sixteen studies from 14 publications met the inclusion criteria. Eligible studies included 847 patients from psychiatric patient trials and 140 healthy subjects from pharmacokinetic studies. Compared to subjects with the EM/EM (CYP2C19*1/*1) genotype, the exposure to (es)citalopram increased by 95 % (95 % CI 40-149, p < 0.0001) in the poor metabolizer (PM)/PM (CYP2C19*2 or *3/*2 or *3), 30 % (95 % CI 4-55, p < 0.05) in the extensive metabolizer (EM)/PM (CYP2C19*1/*2 or *3), and 25 % (95 % CI 1-49, p < 0.05) in the ultrarapid metabolizer (UM)/PM (CYP2C19*17/*2 or *3) groups. In contrast, the exposure to (es)citalopram decreased by 36 % (95 % CI 27-46, p < 0.0001) in the UM/UM (CYP2C19*17/*17) and by 14 % (95 % CI 1-27, p < 0.05) in the UM/EM (CYP2C19*17/*1).
  
  
  CONCLUSIONS
  This is the first meta-analysis based on a systematic review of accumulated information that addresses the relationship between CYP2C19 genotypes and the exposure to citalopram or escitalopram. All functional CYP2C19 genotype groups demonstrated significant effects on (es)citalopram exposure. The findings based on our pooled analysis are likely to help in understanding the inter-individual variability in the exposure to citalopram and escitalopram in psychiatric patients and to facilitate dose selection, particularly for the homozygous carriers of CYP2C19*2 or *3 (loss of function) and CYP2C19*17 (gain of function) alleles. The results could improve individualization of citalopram or escitalopram therapy and could also be used for physiologically based pharmacokinetic modeling as well as pharmacokinetic/pharmacodynamic modeling.
authors.affiliation: Division of Clinical Pharmacology, Department of Laboratory Medicine, Karolinska University Hospital, Huddinge C1:68, SE-141 86, Stockholm, Sweden, ming.chang@ki.se.
authors.forename: Ming
authors.initials: M
authors.lastname: Chang
authors.forename: Gunnel
authors.initials: G
authors.lastname: Tybring
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Dahl
authors.forename: Jonatan D
authors.initials: JD
authors.lastname: Lindh
mesh_terms: D015283:Citalopram / Q000493:pharmacokinetics*; D065731:Cytochrome P-450 CYP2C19 / Q000235:genetics*; D005838:Genotype; D006801:Humans; D011110:Polymorphism, Genetic; D017367:Selective Serotonin Reuptake Inhibitors / Q000493:pharmacokinetics*
chemical_list: D015283:Citalopram; D065731:Cytochrome P-450 CYP2C19; D017367:Selective Serotonin Reuptake Inhibitors; C045793:CYP2C19 protein, human