title: Effect of 300- and 450-mg clopidogrel loading doses on membrane and soluble P-selectin in patients undergoing coronary stent implantation.
abstract: BACKGROUND
  After coronary artery stent implantation patients are treated with the adenosine diphosphatase (ADP) receptor antagonist clopidogrel to prevent subacute stent thromboses. Today these patients initially receive a loading dose of 300 mg of clopidogrel to accelerate the complete drug effect. In the current study we investigated whether a higher loading dose can shorten the time until the maximum platelet inhibitory effect of clopidogrel is achieved.
  
  
  METHODS
  P-selectin expression of nonstimulated and ADP-stimulated platelets was flow cytometrically measured before the clopidogrel loading dose and on 3 consecutive days in 52 patients with coronary artery disease: 21 patients in group 1 received 300 mg of clopidogrel after stent implantation and 11 patients in group 2 received the higher 450-mg clopidogrel loading dose followed by a daily dose of 75 mg of clopidogrel for both groups. The control group consisted of 20 patients who were monitored over 2 days before coronary intervention. Soluble P-selectin levels in plasma were determined by an enzyme-linked immunosorbent assay.
  
  
  RESULTS
  Inducible P-selectin expression on ADP-stimulated platelets was significantly reduced (P =.05) on days 1 and 2 in patient group 2 (450-mg loading dose) compared with group 1 (300-mg loading dose). No influence of clopidogrel on the P-selectin levels in plasma was observed.
  
  
  CONCLUSIONS
  In our study the application of 450 mg of clopidogrel as the loading dose in patients undergoing coronary stenting shortens the period until the maximum effect of the ADP receptor antagonist is achieved and thus may lead to a more successful prevention of subacute coronary stent thromboses.
authors.affiliation: Department of Pneumology, University of Leipzig, Leipzig, Germany.
authors.forename: Hans-Juergen
authors.initials: HJ
authors.lastname: Seyfarth
authors.forename: Mario
authors.initials: M
authors.lastname: Koksch
authors.forename: Gerd
authors.initials: G
authors.lastname: Roethig
authors.forename: Traugott
authors.initials: T
authors.lastname: Rother
authors.forename: Annerose
authors.initials: A
authors.lastname: Neugebauer
authors.forename: Norbert
authors.initials: N
authors.lastname: Klein
authors.forename: Dietrich
authors.initials: D
authors.lastname: Pfeiffer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015906:Angioplasty, Balloon, Coronary / Q000009:adverse effects; D001081:Apyrase / Q000037:antagonists & inhibitors; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D000077144:Clopidogrel; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019007:P-Selectin / Q000187:drug effects* / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D011446:Prospective Studies; D015607:Stents / Q000009:adverse effects*; D013927:Thrombosis / Q000209:etiology / Q000517:prevention & control*; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology*
chemical_list: D019007:P-Selectin; D010975:Platelet Aggregation Inhibitors; D000077144:Clopidogrel; D001081:Apyrase; D013988:Ticlopidine