title: Justification of 150 mg clopidogrel in patients with high on-clopidogrel platelet reactivity.
abstract: BACKGROUND
  The GRAVITAS trial showed that 150 mg clopidogrel did not improve outcome in patients with high on-clopidogrel platelet reactivity (HPR) screened by the VerifyNow assay. We aimed to determine the impact of 150 mg clopidogrel in stable angina patients with HPR identified with conventional aggregometry (LTA).
  
  
  METHODS
  Clopidogrel-naive stable angina patients before ad hoc percutaneous coronary intervention were recruited into a randomized, double-blind, placebo-controlled trial (NCT00638326). Twelve to 24 h after the 600-mg loading dose of clopidogrel, ADP(5μM)-stimulated maximal (AGGmax), late platelet aggregation (AGGlate) and vasodilator-stimulated phosphoprotein phosphorylation (VASP-PRI) were evaluated. Patients with HPR (AGGmax ≥ 34%) were randomly allocated to 75 or 150 mg clopidogrel after 4 weeks. After control platelet function measurements at day 28, 75 mg clopidogrel was administered to all patients until 1 year.
  
  
  RESULTS
  The study was prematurely terminated at the stage of 200 enroled patients. Administration of 150 mg clopidogrel significantly reduced platelet aggregation (AGGmax: 45·0 ± 6·8 vs. 33·8 ± 15·1, P < 0·01; AGGlate: 27·1 ± 14·7 vs. 13·8 ± 18·0, P < 0·01) and VASP-PRI (57·5 ± 15·2 vs. 37·2 ± 17·1; P < 0·01), while platelet reactivity remained unchanged in patients with HPR receiving 75 mg clopidogrel. The higher maintenance dose of clopidogrel was associated with a significant reduction in cardiovascular (CV) death and myocardial infarction (MI) (0% vs. 11·4%, P = 0·04) and in CV death, MI or target vessel revascularization (24·6% vs. 3·1%; P = 0·01) during 1 year.
  
  
  CONCLUSIONS
  One-month administration of 150 mg maintenance dose of clopidogrel reduces platelet reactivity and might decrease the risk of thrombo-ischaemic complications in stable angina patients with HPR identified by LTA.
authors: Heart Institute, University of Pécs, Pécs, Hungary. daniel_aradi@yahoo.com
authors: Dániel
authors: D
authors: Aradi
authors: Orsolya
authors: O
authors: Rideg
authors: András
authors: A
authors: Vorobcsuk
authors: Tamás
authors: T
authors: Magyarlaki
authors: Balázs
authors: B
authors: Magyari
authors: Attila
authors: A
authors: Kónyi
authors: Tünde
authors: T
authors: Pintér
authors: Iván G
authors: IG
authors: Horváth
authors: András
authors: A
authors: Komócsi
mesh_terms: D000368:Aged; D060050:Angina, Stable / Q000188:drug therapy*; D001792:Blood Platelets / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000187:drug effects*; D000077144:Clopidogrel; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008840:Microfilament Proteins / Q000187:drug effects*; D008875:Middle Aged; D010750:Phosphoproteins / Q000187:drug effects*; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage*; D010979:Platelet Function Tests; D020521:Stroke / Q000517:prevention & control; D013927:Thrombosis / Q000517:prevention & control; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D013997:Time Factors; D000098662:Vasodilator-Stimulated Phosphoprotein
chemical_list: D015815:Cell Adhesion Molecules; D008840:Microfilament Proteins; D010750:Phosphoproteins; D010975:Platelet Aggregation Inhibitors; D000098662:Vasodilator-Stimulated Phosphoprotein; D000077144:Clopidogrel; D013988:Ticlopidine