title: Clinical pharmacokinetics of clopidogrel and its metabolites in patients with cardiovascular diseases.
abstract: OBJECTIVE
  Approximately 5-40 % of patients treated with clopidogrel do not display an adequate antiplatelet response. Clopidogrel resistance may be caused by insufficient drug absorption or impaired metabolic activation of the drug. The aim of this study was to evaluate the pharmacokinetics of clopidogrel and its metabolites in plasma samples from patients treated with high and low doses of clopidogrel, to obtain a possible explanation for antiplatelet resistance.
  
  
  METHODS
  The study included patients receiving either a single 300 mg loading dose of clopidogrel (n = 17) or a 75 mg dose (n = 45) for at least 7 days before sample collection. The concentrations of clopidogrel and its metabolites-the inactive H3 and the pharmacologically active H4 isomers of the thiol metabolite and the inactive carboxylic acid metabolite-in plasma samples (stabilized with 2-bromo-3'-methoxyacetophenone) from three patients after 300 mg and from 41 patients after 75 mg of the drug were determined using a validated high-performance liquid chromatography method with tandem mass spectrometry. The non-stabilized samples from the remaining patients were analysed using a validated capillary electrophoresis method. The calculated concentrations were used to determine the pharmacokinetic parameters of the analytes. The pharmacodynamic response to clopidogrel treatment, expressed as adenosine diphosphate-induced platelet aggregation, was measured using a Multiplate analyser.
  
  
  RESULTS
  The pharmacokinetic parameter values for the H3 and H4 isomers determined in the studied group of patients treated with clopidogrel 75 mg (maximum plasma concentration [C max] 5.29 ± 5.54 and 7.13 ± 6.32 ng/mL for H3 and H4, respectively; area under the plasma concentration-time curve from time zero to time t [AUC t ] 7.37 ± 6.71 and 11.30 ± 9.58 ng·h/mL for H3 and H4, respectively) were lower than those reported in healthy volunteers, according to the literature data. Platelet aggregation measured with a Multiplate analyser ranged between 37 and 747 AU·min. A significant correlation was found between the C max of the active H4 isomer and platelet aggregation (p = 0.025).
  
  
  CONCLUSIONS
  The C max of the active H4 isomer and platelet aggregation measured by the Multiplate analyser may serve as markers of the patient response to clopidogrel therapy.
authors.affiliation: Department of Physical Pharmacy and Pharmacokinetics, Poznan University of Medical Sciences, 6 Święcickiego Street, 60-781, Poznan, Poland, mkaraz@ump.edu.pl.
authors.forename: Marta
authors.initials: M
authors.lastname: Karaźniewicz-Łada
authors.forename: Dorota
authors.initials: D
authors.lastname: Danielak
authors.forename: Paweł
authors.initials: P
authors.lastname: Burchardt
authors.forename: Lukasz
authors.initials: L
authors.lastname: Kruszyna
authors.forename: Anna
authors.initials: A
authors.lastname: Komosa
authors.forename: Maciej
authors.initials: M
authors.lastname: Lesiak
authors.forename: Franciszek
authors.initials: F
authors.lastname: Główka
mesh_terms: D000368:Aged; D002318:Cardiovascular Diseases / Q000188:drug therapy / Q000378:metabolism*; D000077144:Clopidogrel; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine