title: Clopidogrel did not inhibit platelet function early after coronary bypass surgery: A prospective randomized trial.
abstract: OBJECTIVE
  Although the beneficial effect of aspirin prescription after coronary surgery has been established, the efficacy of clopidogrel has never been compared with that of aspirin in the critical early postoperative period. We therefore conducted a prospective, double-blind, randomized controlled trial to compare the efficacies of these antiplatelet regimens.
  
  
  METHODS
  Patients undergoing elective primary coronary artery bypass surgery were invited to participate. After the operation, patients were randomized to receive 100 mg aspirin, 325 mg aspirin, or 75 mg clopidogrel tablets daily for 5 days. Our primary outcome measure was platelet aggregation on day 5, expressed as percentage of baseline. Assessment of platelet aggregation was undertaken with the technique of Born.
  
  
  RESULTS
  From September 2002 to July 2003, a total of 54 patients were randomized into the study. There were 2 self-withdrawals and 2 protocol violations, leaving 50 patients for analysis, 34 in the aspirin group and 16 in the clopidogrel arm. Compared with baseline, the mean percentage aggregations with collagen on day 5 were 56% for aspirin and 99% for clopidogrel. The mean difference between the two arms was 42% (95% confidence interval 27%-56%) in favor of aspirin. At the same time point, the effective concentration to inhibit 50% aggregation in the samples from patients randomly assigned to receive clopidogrel were not raised for our entire panel of agonists (changes of -0.04 microg/L for collagen, -0.01 micromol/L for epinephrine, and -0.02 micromol/L for adenosine diphosphate).
  
  
  CONCLUSIONS
  Clopidogrel, unlike aspirin, did not inhibit platelet aggregation in the first 5 postoperative days and therefore should not be used as a sole antiplatelet agent early after coronary surgery.
authors.affiliation: Departments of Cardiothoracic Surgery and Clinical Pharmacology, Papworth Hospital, Cambridge, UK. eric.lim@cvsnet.org
authors.forename: Eric
authors.initials: E
authors.lastname: Lim
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Cornelissen
authors.forename: Tom
authors.initials: T
authors.lastname: Routledge
authors.forename: Stephen
authors.initials: S
authors.lastname: Kirtland
authors.forename: Susan C
authors.initials: SC
authors.lastname: Charman
authors.forename: Sarah
authors.initials: S
authors.lastname: Bellm
authors.forename: Helen
authors.initials: H
authors.lastname: Munday
authors.forename: Omar
authors.initials: O
authors.lastname: Khan
authors.forename: Imran
authors.initials: I
authors.lastname: Masood
authors.forename: Stephen
authors.initials: S
authors.lastname: Large
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage*; D001241:Aspirin / Q000008:administration & dosage*; D000077144:Clopidogrel; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D011446:Prospective Studies; D013988:Ticlopidine / Q000008:administration & dosage* / Q000031:analogs & derivatives*
chemical_list: D000925:Anticoagulants; D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin