title: Impact of P-glycoprotein on clopidogrel absorption.
abstract: OBJECTIVE
  The antiplatelet activity of clopidogrel is characterized by considerable interindividual differences. Variable intestinal absorption is suggested to contribute to the inconsistencies in response. We tested the hypothesis that the intestinal efflux transporter P-glycoprotein (P-gp) limits the oral bioavailability of clopidogrel and that variance in the MDR1 gene encoding P-gp predicts absorption variability.
  
  
  RESULTS
  P-gp-mediated transport of clopidogrel was assessed by transflux, influx, and efflux experiments by use of Caco-2 cells. Inhibition of P-gp activity by different modulators increased the absorptive clopidogrel flux across Caco-2 monolayers from 0.51+/-0.19 pmol/cm2 (mean+/-SD) at baseline by a maximum of 5- to 9-fold (P<.001) and the intracellular accumulation from 0.99+/-0.11 pmol/mg protein by a maximum of 2.5-fold (P<.001) in response to 1-micromol/L clopidogrel and decreased clopidogrel efflux to the level of passive diffusion. In 60 patients with coronary artery disease who underwent percutaneous coronary intervention, the peak plasma concentration (Cmax) and the total area under the plasma concentration-time curve (AUC) of clopidogrel and its active metabolite after a single oral loading dose of 300, 600, or 900 mg were tested for correlation with the MDR1 genotype. In the 300-mg and 600-mg groups (but not in the 900-mg group) Cmax and AUC values were lower in subjects homozygous for the MDR1 3435T variant compared with subjects with the 3435C/T and 3435C/C genotypes. After the 600-mg loading dose, Cmax values (mean+/-SD) of clopidogrel and its active metabolite in 3435T/T carriers were 13.3+/-5.2 ng/mL and 2.5+/-1.2 ng/mL, respectively, compared with 49.7+/-41.6 ng/mL (P=.001) and 6.6+/-3.6 ng/mL (P=.011), respectively, in 3435C/T and 3435C/C carriers; AUC values were 1502+/-463 ng/mLxmin for clopidogrel and 209+/-99 ng/mL x min for its active metabolite in 3435T/T carriers compared with 7057+/-5443 ng/mLxmin (P=.0006) and 744+/-541 ng/mLxmin (P=.011), respectively, in 3435C/T and 3435C/C carriers.
  
  
  CONCLUSIONS
  Clopidogrel absorption and thereby active metabolite formation are diminished by P-gp-mediated efflux and are influenced by the MDR1 C3435T genotype.
authors.affiliation: Institut für Pharmakologie, Klinikum I für Innere Medizin, Cologne, and Deutsches Herzzentrum, Technische Universität München, Munich, Germany. dirk.taubert@medizin.uni-koeln.de
authors.forename: Dirk
authors.initials: D
authors.lastname: Taubert
authors.forename: Nicolas
authors.initials: N
authors.lastname: von Beckerath
authors.forename: Gundula
authors.initials: G
authors.lastname: Grimberg
authors.forename: Andreas
authors.initials: A
authors.lastname: Lazar
authors.forename: Norma
authors.initials: N
authors.lastname: Jung
authors.forename: Tobias
authors.initials: T
authors.lastname: Goeser
authors.forename: Adnan
authors.initials: A
authors.lastname: Kastrati
authors.forename: Albert
authors.initials: A
authors.lastname: Schömig
authors.forename: Edgar
authors.initials: E
authors.lastname: Schömig
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000284:Administration, Oral; D019540:Area Under Curve; D001682:Biological Availability; D018938:Caco-2 Cells; D002463:Cell Membrane Permeability / Q000187:drug effects; D000077144:Clopidogrel; D003324:Coronary Artery Disease / Q000235:genetics / Q000378:metabolism* / Q000628:therapy; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D005838:Genotype; D006801:Humans; D007408:Intestinal Absorption; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000378:metabolism / Q000493:pharmacokinetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D010975:Platelet Aggregation Inhibitors; D012333:RNA, Messenger; D000077144:Clopidogrel; D013988:Ticlopidine