title: Clopidogrel pharmacokinetics and pharmacodynamics vary widely despite exclusion or control of polymorphisms (CYP2C19, ABCB1, PON1), noncompliance, diet, smoking, co-medications (including proton pump inhibitors), and pre-existent variability in platelet function.
abstract: OBJECTIVE
  This study sought to determine whether known genetic, drug, dietary, compliance, and lifestyle factors affecting clopidogrel absorption and metabolism fully account for the variability in clopidogrel pharmacokinetics and pharmacodynamics.
  
  
  BACKGROUND
  Platelet inhibition by clopidogrel is highly variable. Patients with reduced inhibition have increased risk for major adverse cardiovascular events. Identification of factors contributing to clopidogrel's variable response is needed to improve platelet inhibition and reduce risk for cardiovascular events.
  
  
  METHODS
  Healthy subjects (n = 160; ages 20 to 53 years; homozygous CYP2C19 extensive metabolizer genotype; no nicotine for 6 weeks, prescription drugs for 4 weeks, over-the-counter drugs for 2 weeks, and no caffeine or alcohol for 72 h; confined; restricted diet) received clopidogrel 75 mg/day for 9 days, at which time clopidogrel pharmacokinetic and pharmacodynamic endpoints were measured.
  
  
  RESULTS
  At steady-state, clopidogrel active metabolite (clopidogrel(AM)) pharmacokinetics varied widely between subjects (coefficients of variation [CVs] 33.8% and 40.2% for clopidogrel(AM) area under the time-concentration curve and peak plasma concentration, respectively). On-treatment vasodilator stimulated phosphoprotein P2Y(12) platelet reactivity index (PRI), maximal platelet aggregation (MPA) to adenosine phosphate, and VerifyNow P2Y12 platelet response units (PRU) also varied widely (CVs 32% to 53%). All identified factors together accounted for only 18% of intersubject variation in pharmacokinetic parameters and 32% to 64% of intersubject variation in PRI, MPA, and PRU. High on-treatment platelet reactivity was present in 45% of subjects.
  
  
  CONCLUSIONS
  Clopidogrel pharmacokinetics and pharmacodynamics vary widely despite rigorous exclusion or control of known disease, polymorphisms (CYP2C19, CYP3A5, ABCB1, PON1), noncompliance, co-medications, diet, smoking, alcohol, demographics, and pre-treatment platelet hyperreactivity. Thus, as yet unidentified factors contribute to high on-treatment platelet reactivity with its known increased risk of major adverse cardiovascular events. (A Study of the Effects of Multiple Doses of Dexiansoprazole, Lansoprazole, Omeprazole or Esomeprazole on the Pharmacokinetics and Pharmacodynamics of Clopidogrel in Healthy Participants: NCT00942175).
authors: Center for Platelet Research Studies, Division of Hematology/Oncology, Boston Children's Hospital, Dana-Farber Cancer Institute, Boston, Massachusetts, USA. Andrew.Frelinger@childrens.harvard.edu
authors: Andrew L
authors: AL
authors: Frelinger
authors: Deepak L
authors: DL
authors: Bhatt
authors: Ronald D
authors: RD
authors: Lee
authors: Darcy J
authors: DJ
authors: Mulford
authors: Jingtao
authors: J
authors: Wu
authors: Sai
authors: S
authors: Nudurupati
authors: Anu
authors: A
authors: Nigam
authors: Michael
authors: M
authors: Lampa
authors: Julie K
authors: JK
authors: Brooks
authors: Marc R
authors: MR
authors: Barnard
authors: Alan D
authors: AD
authors: Michelson
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles / Q000008:administration & dosage / Q000493:pharmacokinetics; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics; D000328:Adult; D019540:Area Under Curve; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics; D043303:Aryldialkylphosphatase / Q000235:genetics; D001777:Blood Coagulation / Q000187:drug effects; D002318:Cardiovascular Diseases / Q000097:blood / Q000209:etiology / Q000517:prevention & control* / Q000523:psychology; D000077144:Clopidogrel; D015986:Confounding Factors, Epidemiologic; D018592:Cross-Over Studies; D065731:Cytochrome P-450 CYP2C19; D004347:Drug Interactions; D016903:Drug Monitoring / Q000379:methods; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance; D010974:Platelet Aggregation / Q000187:drug effects / Q000235:genetics; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics; D010979:Platelet Function Tests / Q000379:methods; D011110:Polymorphism, Genetic; D054328:Proton Pump Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics; D012907:Smoking / Q000378:metabolism; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D010975:Platelet Aggregation Inhibitors; D054328:Proton Pump Inhibitors; D000077144:Clopidogrel; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D043303:Aryldialkylphosphatase; C468406:PON1 protein, human; D013988:Ticlopidine