title: Increased platelet inhibition after switching from maintenance clopidogrel to prasugrel in patients with acute coronary syndromes: results of the SWAP (SWitching Anti Platelet) study.
abstract: OBJECTIVE
  The objective was to evaluate the pharmacodynamic response of switching patients on maintenance phase clopidogrel therapy after an acute coronary syndrome (ACS) to prasugrel.
  
  
  BACKGROUND
  Prasugrel P2Y(12) receptor blockade is associated with greater pharmacodynamic platelet inhibition and reduction of ischemic complications compared with that of clopidogrel in ACS patients undergoing percutaneous coronary intervention. The pharmacodynamic effects of switching patients during maintenance phase clopidogrel therapy after an ACS event to prasugrel are unknown.
  
  
  METHODS
  The SWAP (SWitching Anti Platelet) study was a phase 2, multicenter, randomized, double-blind, double-dummy, active-control trial. After a run-in of daily open-label clopidogrel 75 mg with aspirin therapy for 10 to 14 days, patients were randomly assigned to 1 of the following 3 treatments: placebo loading dose (LD)/clopidogrel 75 mg maintenance dose (MD), placebo LD/prasugrel 10 mg MD, or prasugrel 60 mg LD/10 mg MD. Platelet function was evaluated at 2 h, 24 h, 7 days, and 14 days using light transmittance aggregometry, VerifyNow P2Y(12) assay, and vasodilator-stimulated phosphoprotein phosphorylation.
  
  
  RESULTS
  A total of 139 patients were randomized, of whom 100 were eligible for analysis. Maximum adenosine diphosphate-induced platelet aggregation (20 μM) by light transmittance aggregometry at 1 week (primary end point) was lower after prasugrel MD compared with clopidogrel MD (41.1% vs. 55.0%, p < 0.0001), and was also lower in the prasugrel LD+MD group compared with clopidogrel MD (41.0% vs. 55.0%, p < 0.0001). At 2 h, a prasugrel LD resulted in higher platelet inhibition compared with the other regimens. Similar results were found using light transmittance aggregometry with 5 μM adenosine diphosphate, VerifyNow P2Y(12), and vasodilator-stimulated phosphoprotein phosphorylation assays.
  
  
  CONCLUSIONS
  For patients receiving maintenance clopidogrel therapy after an ACS event, switching from clopidogrel to prasugrel is associated with a further reduction in platelet function by 1 week using prasugrel MD or within 2 h with the administration of a prasugrel LD. (A Pharmacodynamic Comparison of Prasugrel [LY640315] Versus Clopidogrel in Subjects With Acute Coronary Syndrome Who Are Receiving Clopidogrel [SWAP]; NCT00356135).
authors.affiliation: University of Florida College of Medicine, Jacksonville, Florida 32209, USA. dominick.angiolillo@jax.ufl.edu
authors.forename: Dominick J
authors.initials: DJ
authors.lastname: Angiolillo
authors.forename: Jorge F
authors.initials: JF
authors.lastname: Saucedo
authors.forename: Roger
authors.initials: R
authors.lastname: Deraad
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Frelinger
authors.forename: Paul A
authors.initials: PA
authors.lastname: Gurbel
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Costigan
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Jakubowski
authors.forename: Clement K
authors.initials: CK
authors.lastname: Ojeh
authors.forename: Mark B
authors.initials: MB
authors.lastname: Effron
mesh_terms: D054058:Acute Coronary Syndrome / Q000178:diet therapy*; D000368:Aged; D015906:Angioplasty, Balloon, Coronary; D001792:Blood Platelets / Q000187:drug effects*; D000077144:Clopidogrel; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010879:Piperazines / Q000008:administration & dosage / Q000493:pharmacokinetics*; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000068799:Prasugrel Hydrochloride; D013876:Thiophenes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000493:pharmacokinetics
chemical_list: D010879:Piperazines; D010975:Platelet Aggregation Inhibitors; D013876:Thiophenes; D000077144:Clopidogrel; D000068799:Prasugrel Hydrochloride; D013988:Ticlopidine