Factors associated with the failure of clopidogrel dose-adjustment according to platelet reactivity monitoring to optimize P2Y12-ADP receptor blockade.

INTRODUCTION: Inter-individual variability in clopidogrel responsiveness is dependent on genetic polymorphisms. We aimed to investigate the impact of 3 genetic polymorphisms involved in clopidogrel metabolism on a strategy of dose-adjustment according to platelet reactivity (PR) monitoring. MATERIAL AND METHODS: [corrected] This prospective multicenter study enrolled 498 ACS patients undergoing PCI. PR was measured using the Vasodilator-Stimulated Phosphoprotein index (VASP) and a cut-off value of ≥50% defined high on-treatment platelet reactivity (HTPR). Genetic polymorphisms of cytochrome (CYP) 2C19, Paraxonase-1 (PON1) and ABCB1 were determined by allele specific PCR. Dose-adjustment was performed using up-to 3 additional loading doses (LD) of 600mg clopidogrel in order to obtain a VASP <50% in patients with HTPR following the first LD. RESULTS: CYP 2C19 2*polymorphism (p=0.02), but neither PON1 (p=0.8) nor ABCB1 genotype (p=0.9), was significantly associated with HTPR. The dose-adjustment strategy failed in 11% of patients. ABCB1 polymorphism was significantly associated with a failed dose-adjustment (FDA) (p=0.04). No relation was found between the other genotypes and the efficacy of LD adjustment. In multivariate analysis, BMI and ABCB1 polymorphism were the only factors significantly associated with FDA (p=0.005 and p=0.04 respectively). CONCLUSION: While CYP 2C19 2* is associated with HTPR after 600mg of clopidogrel, ABCB1 is responsible for the failure of a strategy of loading dose-adjustment according to PR monitoring. These findings may help to define a therapeutic strategy to optimize anti-platelet therapy in ACS patients undergoing PCI.

Rate of nuisance bleedings and impact on compliance to prasugrel in acute coronary syndromes.

Antiplatelet agents are critical to prevent thrombotic events in patients with acute coronary syndromes, particularly those who undergo percutaneous coronary intervention. Prasugrel is a potent P2Y(12)-adenosine diphosphate receptor antagonist that is superior to clopidogrel in such patients. Previous studies have observed that nuisance and internal bleedings were relatively frequent in patients under clopidogrel therapy and were associated with noncompliance. Furthermore, premature drug discontinuation is associated with thrombotic recurrences. The aim of the present study was to investigate the rate of nuisance or internal bleedings in patients receiving prasugrel and its relation with compliance. This prospective multicenter study included 396 patients. Bleeding events were recorded and classified as alarming, nuisance, or internal according. Compliance with prasugrel therapy was assessed. Almost half of the patients (48.5%) were included for ST-segment elevation acute coronary syndromes. During the 1-month follow-up period, 54 patients (13.6%) had bleeding events. Most bleeding events were classified as internal or nuisance (96%). Internal and nuisance bleedings were associated with high rates of prasugrel discontinuation (16.6% and 14.7%, respectively). Nuisance and internal bleedings were significantly associated with prasugrel discontinuation in multivariate analysis (odds ratio 3.1, 95% confidence interval 1.01 to 9.2, p = 0.04). The rate of major adverse cardiovascular events was 2.3%. No relation was observed between minor bleeds, compliance, and major adverse cardiovascular events. In conclusion, in the present study, minor bleedings were common during the first month after percutaneous coronary intervention and were significantly associated with prasugrel withdrawal.