title: Effect of 150-mg vs 300-mg loading doses of clopidogrel on platelet function in Japanese patients undergoing coronary stent placement.
abstract: BACKGROUND
  The loading dose of ticlopidine is 500 mg in both the US and Europe and 200 mg in Japan. A lower loading dose of clopidogrel might achieve adequate platelet inhibition in Japanese patients.
  
  
  RESULTS
  Platelet aggregation was serially measured at baseline, and 2, 4, 6, and 8 h after 150-mg (n=20) and 300-mg (n=20) clopidogrel loading. Platelets were stimulated with 5 and 20 micromol/L adenosine diphosphate (ADP) and aggregation was assessed by optical aggregometry. Pretreatment ADP-induced platelet aggregation in the 150-mg clopidogrel group did not differ from that of the 300-mg group. The administration of 300-mg clopidogrel loading dose resulted in lower platelet aggregation 2 h after the administration (5 micromol/L ADP: 53+/-9% vs 61+/-12%, p<0.05 and 20 micromol/L ADP: 61+/-10% vs 68+/-9%, p<0.05). A lower platelet aggregation induced with 20 micromol/L ADP was still observed 4 h after the 300-mg clopidogrel loading (58+/-10% vs 65+/-9%, p<0.05).
  
  
  CONCLUSIONS
  The 150-mg clopidogrel loading does not achieve rapid platelet inhibition. The 300-mg loading dose should be used to suppress platelet function rapidly even in Japanese patients undergoing coronary stent placement.
authors.affiliation: Department of Cardiovascular Science and Medicine, Chiba University Graduate School of Medicine, Chiba, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Fukushima
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Hideki
authors.initials: H
authors.lastname: Kitahara
authors.forename: Yo
authors.initials: Y
authors.lastname: Iwata
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakayama
authors.forename: Nakabumi
authors.initials: N
authors.lastname: Kuroda
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ooyama
authors.forename: Fumio
authors.initials: F
authors.lastname: Nomura
authors.forename: Issei
authors.initials: I
authors.lastname: Komuro
mesh_terms: D000244:Adenosine Diphosphate; D000368:Aged; D015906:Angioplasty, Balloon, Coronary / Q000009:adverse effects / Q000295:instrumentation; D044466:Asian People; D000077144:Clopidogrel; D003324:Coronary Artery Disease / Q000097:blood / Q000208:ethnology / Q000628:therapy*; D003328:Coronary Thrombosis / Q000097:blood / Q000209:etiology / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D010979:Platelet Function Tests; D015607:Stents; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D010975:Platelet Aggregation Inhibitors; D000244:Adenosine Diphosphate; D000077144:Clopidogrel; D013988:Ticlopidine