Intrinsic platelet reactivity before P2Y(12) blockade contributes to residual platelet reactivity despite high-level P2Y(12) blockade by prasugrel or high-dose clopidogrel Results from PRINCIPLE-TIMI 44
ABSTRACT It was the objective of this study to determine whether the intrinsic platelet response to adenosine diphosphate (ADP) before thienopyridine exposure contributes to residual platelet reactivity to ADP despite high level P2Y12 blockade by prasugrel (60 mg loading dose [LD]), 10 mg daily maintenance dose [MD]) or high-dose clopidogrel (600 mg LD, 150 mg daily MD). High residual platelet function during clopidogrel therapy is associated with poor clinical outcomes. It remains unknown whether the relationship between platelet reactivity prior to treatment with clopidogrel (300 mg LD, 75 mg daily MD) and residual on-treatment platelet reactivity is maintained after more potent P2Y12 inhibition. PRINCIPLE-TIMI 44 was a randomised, double-blind, two-phase crossover study of prasugrel compared with high-dose clopidogrel in 201 patients undergoing cardiac catheterisation for planned percutaneous coronary intervention. ADP-stimulated platelet-monocyte aggregates, platelet surface P-selectin and platelet aggregation were measured pre-treatment, during LD (6 h and 18-24 h) and MD (15 d). Correlations of pre-treatment to on-treatment values were determined by Spearman rank order. Prasugrel resulted in greater platelet inhibition than high-dose clopidogrel for each measure. However, for both drugs, pre-treatment reactivity to ADP predicted 6 h, 18-24 h and 15 day reactivity to ADP (correlations 0.24-0.62 for platelet-monocyte aggregates and P-selectin). In conclusion, a patient's intrinsic platelet response to ADP before exposure to thienopyridines contributes to residual platelet reactivity to ADP despite high level P2Y12 blockade with high-dose clopidogrel or even higher level P2Y12 blockade with prasugrel. Patients who are hyper-responsive to ADP pre-treatment are more likely to be hyper-responsive to ADP on-treatment, which may be relevant to therapeutic strategies.
- Thrombosis and Haemostasis 08/2011; 106(2):189-90. DOI:10.1160/TH11-07-0467 · 5.76 Impact Factor
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ABSTRACT: Combined inhibition of platelet aggregation is essential to prevent recurrent ischemic episodes in patients with acute coronary syndromes and after percutaneous coronary interventions (PCIs). In combination with aspirin, the ADP receptor antagonist clopidogrel is used widespread for this purpose; however, platelet reactivity after clopidogrel differs substantially between patients and high on-treatment platelet reactivity (HTPR) persists in a substantial proportion of cases. Since more than 20 prior observational studies linked HTPR to higher risk of ischemic events, including cardiovascular death, myocardial infarction, and stent thrombosis, monitoring post-clopidogrel platelet reactivity after PCI might be beneficial for risk assessment and to tailor the antiplatelet therapy to the patients' needs. However, there is no consensus on the role of routine platelet function monitoring in clinical guidelines. This article aims to review the available evidence regarding the clinical relevance of platelet function monitoring, highlighting possible reasons for the controversy between guidelines and observational studies.Platelets 09/2011; 23(3):167-76. DOI:10.3109/09537104.2011.610475 · 2.63 Impact Factor
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ABSTRACT: Although there is considerable variability of platelet reactivity among patients treated with clopidogrel, little is known about inter-individual differences and possible role of proton pump inhibitors (PPIs) after prasugrel. We defined the extent of inter-patient variability, and evaluated the impact of PPI interaction in prasugrel-treated patients with acute coronary syndrome (ACS). Between January 2010 and May 2011, 104 prospective, high-risk patients with ACS were recruited into this multicentre, prospective, observational study. Twelve to 24 hours after receiving 60 mg loading dose of prasugrel, light transmission aggregometry (LTA) and whole blood impedance aggregometry (Multiplate) were used to assess platelet activity. Platelet function measurements were repeated during maintenance phase on reduced (5 mg) or on conventional (10 mg) doses of prasugrel. High platelet reactivity (HPR) was defined according to the consensus document of the Working Group on High On-Treatment Platelet Reactivity (LTA:>46%; Multiplate:>47U). Compared to maintenance doses, 60 mg loading dose of prasugrel provided significantly greater platelet reactivity inhibition (p<0.05). There were no significant differences between the conventional and reduced maintenance doses. Notably, a remarkable inter-patient variability was present in platelet reactivity after all doses of prasugrel, and the prevalence of HPR was significantly higher during the maintenance doses (p<0.05). Although median platelet reactivity values were consistently higher when prasugrel was used in combination with PPIs, these differences were not significant (p≥0.17). Despite potent platelet inhibition, inter-patient variability is present after all tested doses of prasugrel. The 60 mg loading dose is superior to conventional and reduced maintenance doses in terms of platelet reactivity inhibition and regarding the prevention of HPR.Thrombosis and Haemostasis 12/2011; 107(2):338-45. DOI:10.1160/TH11-09-0622 · 5.76 Impact Factor