title: Aspirin and clopidogrel drug response in patients undergoing percutaneous coronary intervention: the role of dual drug resistance.
abstract: We evaluated the response to clopidogrel among aspirin-resistant versus aspirin-sensitive patients undergoing elective coronary stenting. Patients (n = 150) treated with aspirin but not clopidogrel had blood samples drawn at baseline and 24 h after clopidogrel loading. Depending on the definition used, 9% to 15% were resistant to aspirin and 24% to clopidogrel. About half of the aspirin-resistant patients were also resistant to clopidogrel. As a group, aspirin-resistant patients had lower response to clopidogrel (assessed by platelet aggregation and activation markers) than aspirin-sensitive patients. Both aspirin- and clopidogrel-resistant patients had higher incidence of creatine kinase-MB elevation than the respective sensitive patients.
  
  
  OBJECTIVE
  We sought to evaluate the response to clopidogrel among aspirin-resistant versus aspirin-sensitive patients undergoing percutaneous coronary intervention (PCI).
  
  
  BACKGROUND
  Wide variability has been reported in response to aspirin and clopidogrel. There are limited data on the simultaneous responses to both drugs.
  
  
  METHODS
  Elective PCI patients (n = 150) who received aspirin for > or = 1 week but not clopidogrel were included. All patients received bivalirudin during PCI. Blood samples were drawn at baseline and 20 to 24 h after a 300-mg clopidogrel dose. Aspirin resistance was defined by > or = 2 of 3 criteria: rapid platelet function analyzer-ASA score > or = 550, 5 micromol/l adenosine diphosphate (ADP)-induced aggregation > or = 70%, and 0.5 mg/ml arachidonic acid-induced aggregation > or = 20%. Clopidogrel resistance was defined as baseline minus post-treatment aggregation < or = 10% in response to 5 and 20 micromol/l ADP.
  
  
  RESULTS
  Nineteen (12.7%) patients were resistant to aspirin and 36 (24%) to clopidogrel. Nine (47.4%) of the aspirin-resistant patients were also clopidogrel resistant. Aspirin-resistant patients were more likely to be women and have diabetes than were aspirin-sensitive patients. They also had lower response to clopidogrel, assessed by platelet aggregation and activation markers (flow cytometry-determined PAC-1 binding and P-selectin expression). Elevation of creatine kinase-myocardial band after stenting occurred more frequently in aspirin-resistant versus aspirin-sensitive patients (38.9% vs. 18.3%; p = 0.04) and in clopidogrel-resistant versus clopidogrel-sensitive patients (32.4% vs. 17.3%; p = 0.06).
  
  
  CONCLUSIONS
  Aspirin-resistant patients as a group have reduced response to clopidogrel. Furthermore, we have identified a unique group of dual drug-resistant patients who may be at increased risk for thrombotic complications after PCI.
authors.affiliation: Cardiology Section, Methodist DeBakey Heart Center, Houston, Texas 77030, USA.
authors.forename: Eli I
authors.initials: EI
authors.lastname: Lev
authors.forename: Rajnikant T
authors.initials: RT
authors.lastname: Patel
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Maresh
authors.forename: Sasidhar
authors.initials: S
authors.lastname: Guthikonda
authors.forename: Juan
authors.initials: J
authors.lastname: Granada
authors.forename: Timothy
authors.initials: T
authors.lastname: DeLao
authors.forename: Paul F
authors.initials: PF
authors.lastname: Bray
authors.forename: Neal S
authors.initials: NS
authors.lastname: Kleiman
mesh_terms: D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D001241:Aspirin / Q000494:pharmacology*; D000077144:Clopidogrel; D052279:Creatine Kinase, MB Form / Q000097:blood; D018432:Drug Resistance, Multiple; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000097:blood; D015539:Platelet Activation / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D015607:Stents; D013988:Ticlopidine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D019007:P-Selectin; D010975:Platelet Aggregation Inhibitors; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D000077144:Clopidogrel; D052279:Creatine Kinase, MB Form; D013988:Ticlopidine; D001241:Aspirin