title: Effect of CYP2C9, VKORC1, CYP4F2 and GGCX genetic variants on warfarin maintenance dose and explicating a new pharmacogenetic algorithm in South Indian population.
abstract: OBJECTIVE
  To determine the influence of genetic polymorphisms on warfarin maintenance dose and to explicate an algorithm using the pharmacogenetic and clinical factors to determine the maintenance and/or starting dose of warfarin in South Indian patients receiving warfarin therapy.
  
  
  METHODS
  Patients receiving stabilized warfarin therapy (n=257) were included in the study. Single nucleotide polymorphisms (SNPs) of CYP2C9 (rs1799853 and rs1057910), VKORC1 (rs9923231, rs7196161, rs2884737, rs9934438, rs8050894, rs2359612 and rs7294), CYP4F2 (rs2108622) and GGCX (rs11676382) were genotyped by the quantitative real time-PCR method.
  
  
  RESULTS
  The mean daily maintenance dose of warfarin was found to be 4.7 ± 2.1 mg/day. Patients with the CYP2C9*1/*2, *1/*3 and *2/*3 variant genotypes required a 51.0 (2.8 mg), 60.9 (2.3 mg) and 62.2 % (2.2 mg) lower daily maintenance dose of warfarin, respectively, than those patients with the CYP2C9*1/*1 wild-type genotype (5.2 mg) (p<0.0001). The genetic variants of CYP2C9, VKORC1 and GGCX were associated with decreased warfarin dose, except for rs7196161, rs7294 and rs2108622 which were associated with an increased warfarin dose. Genetic variations of CYP2C9 (*2 and *3), VKORC1 (rs9923231, rs7294, rs9934438 and rs2359612), CYP4F2, GGCX and non-genetic factors such as age, body weight, clinical status (post mechanical valve replacement) could explain up to 62.1 % of the overall variation (adjusted r (2) 60.2 %, p<0.0001) in warfarin maintenance dose.
  
  
  CONCLUSIONS
  Genetic polymorphisms of CYP2C9, VKORC1, CYP4F2 and GGCX are important predictive factors of warfarin maintenance dose, and the developed algorithm will be useful to predict the required maintenance and/or starting warfarin dose in South Indian populations.
authors.affiliation: Department of Pharmacology, Jawaharlal Institute of Postgraduate Medical Education & Research (JIPMER), Pondicherry, 605 006, India, krishnakumarrx@hotmail.com.
authors.forename: Dhakchinamoorthi
authors.initials: D
authors.lastname: Krishna Kumar
authors.forename: Deepak Gopal
authors.initials: DG
authors.lastname: Shewade
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Loriot
authors.forename: Philippe
authors.initials: P
authors.lastname: Beaune
authors.forename: Jayaraman
authors.initials: J
authors.lastname: Balachander
authors.forename: B V
authors.initials: BV
authors.lastname: Sai Chandran
authors.forename: Chandrasekaran
authors.initials: C
authors.lastname: Adithan
mesh_terms: D000328:Adult; D000465:Algorithms; D000925:Anticoagulants / Q000008:administration & dosage*; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D019735:Carbon-Carbon Ligases / Q000235:genetics*; D065729:Cytochrome P-450 CYP2C9; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D000072470:Cytochrome P450 Family 4; D005260:Female; D005838:Genotype; D006801:Humans; D007194:India; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D013923:Thromboembolism / Q000235:genetics / Q000517:prevention & control; D064417:Vitamin K Epoxide Reductases / Q000235:genetics*; D014859:Warfarin / Q000008:administration & dosage*; D044465:White People / Q000235:genetics
chemical_list: D000925:Anticoagulants; D014859:Warfarin; D003577:Cytochrome P-450 Enzyme System; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D000072470:Cytochrome P450 Family 4; C117480:CYP4F2 protein, human; C578523:VKORC1 protein, human; D064417:Vitamin K Epoxide Reductases; D019735:Carbon-Carbon Ligases; C020660:glutamyl carboxylase
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