title: Increased risk of atherothrombotic events associated with cytochrome P450 3A5 polymorphism in patients taking clopidogrel.
abstract: BACKGROUND
  Clopidogrel is a prodrug requiring metabolism by cytochrome P450 3A (CYP3A) isoenzymes, including CYP3A5, in order to be active. It is controversial whether clopidogrel interacts with CYP3A inhibitors. We investigated the influence of CYP3A5 polymorphism on the drug interaction of clopidogrel.
  
  
  METHODS
  In phase 1 of the study, we administered clopidogrel to 16 healthy volunteers who had the CYP3A5 non-expressor genotype (*3 allele) and 16 who had the CYP3A5 expressor genotype (*1 allele) with and without pretreatment with itraconazole, a potent CYP3A inhibitor. A platelet aggregation test was performed at baseline, 4 hours, 24 hours and 6 days after clopidogrel administration. In phase 2, we compared clinical outcomes of 348 patients treated with clopidogrel after successful coronary angioplasty with bare-metal stent implantation according to their CYP3A5 genotype; the primary end point was a composite of atherothrombotic events (cardiovascular death, myocardial infarction and non-hemorrhagic stroke) within 1 and 6 months after stent implantation.
  
  
  RESULTS
  In phase 1, the change in platelet aggregation after clopidogrel administration and pretreatment with itraconazole was greater among the subjects with the CYP3A5 expressor genotype than among those with the non-expressor genotype: 24.9% (standard deviation [SD] 13.9%) v. 6.2% (SD 13.5%) at 4 hours (p < 0.001); 27.7% (SD 16.5%) v. 2.5% (SD 8.3%) at 24 hours (p < 0.001); and 33.5% (SD 18.6%) v. 17.8% (SD 13.8%) at day 7 (p < 0.01). In phase 2, atherothrombotic events occurred more frequently within 6 months after stent implantation among the patients with the non-expressor genotype than among those with the expressor genotype (14/193 v. 3/155; p = 0.023). Multivariable analysis showed that the CYP3A5 polymorphism was a predictor of atherothrombotic events in clopidogrel users.
  
  
  CONCLUSIONS
  People with the CYP3A5 non-expressor genotype are vulnerable to drug interactions between clopidogrel and CYP3A inhibitors. This phenomenon may be associated with worse outcomes in patients with the non-expressor genotype who are given clopidogrel after coronary angioplasty and implantation of bare-metal stents.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jung-Won
authors.initials: JW
authors.lastname: Suh
authors.forename: Bon-Kwon
authors.initials: BK
authors.lastname: Koo
authors.forename: Shu-Ying
authors.initials: SY
authors.lastname: Zhang
authors.forename: Kyung-Woo
authors.initials: KW
authors.lastname: Park
authors.forename: Joo-Youn
authors.initials: JY
authors.lastname: Cho
authors.forename: In-Jin
authors.initials: IJ
authors.lastname: Jang
authors.forename: Dong-Soon
authors.initials: DS
authors.lastname: Lee
authors.forename: Dae-Won
authors.initials: DW
authors.lastname: Sohn
authors.forename: Myoung-Mook
authors.initials: MM
authors.lastname: Lee
authors.forename: Hyo-Soo
authors.initials: HS
authors.lastname: Kim
mesh_terms: D000368:Aged; D000077144:Clopidogrel; D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D004347:Drug Interactions; D017700:Embolism, Cholesterol / Q000139:chemically induced*; D004791:Enzyme Inhibitors / Q000009:adverse effects; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000009:adverse effects* / Q000378:metabolism; D011110:Polymorphism, Genetic; D012307:Risk Factors; D013927:Thrombosis / Q000139:chemically induced*; D013988:Ticlopidine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D010975:Platelet Aggregation Inhibitors; D003577:Cytochrome P-450 Enzyme System; D000077144:Clopidogrel; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; D013988:Ticlopidine