Predictors of Heightened Platelet Reactivity Despite Dual-Antiplatelet Therapy in Patients Undergoing Percutaneous Coronary Intervention
Division of Cardiovascular Diseases, Scripps Clinic, La Jolla, California, USA. The American journal of cardiology
(Impact Factor: 3.28).
06/2009; 103(10):1339-43. DOI: 10.1016/j.amjcard.2009.01.341
Small studies have indicated that drug-drug interactions and such clinical characteristics as diabetes mellitus may increase residual platelet reactivity in patients on clopidogrel therapy. The independent contribution of these variables to high residual platelet reactivity (HRPR) is not well studied. Residual platelet reactivity was assessed using the VerifyNow P2Y12 assay (Accumetrics Inc., San Diego, California) in 377 patients with stable coronary artery disease on maintenance clopidogrel therapy. HRPR was defined using a threshold previously shown to predict adverse clinical outcomes. Residual platelet reactivity was significantly higher in women (220 +/- 82 vs 200 +/- 77 P2Y12 reaction units [PRU]; p = 0.041), non-Caucasians (229 +/- 79 vs 202 +/- 78 PRU; p = 0.047), patients with diabetes mellitus (220 +/- 73 vs 196 +/- 80 PRU; p = 0.005), and those treated with nitrates (233 +/- 70 vs 200 +/- 80 PRU; p = 0.018) or proton-pump inhibitors (218 +/- 79 vs 198 +/- 78 PRU; p = 0.02), whereas residual platelet reactivity was significantly lower in active smokers (168 +/- 82 vs 208 +/- 77 PRU; p = 0.006). Independent predictors of HRPR were female gender (odds ratio [OR] 1.91, 95% confidence interval [CI] 1.14 to 3.19, p = 0.014), non-Caucasian ethnicity (OR 3.05, 95% CI 1.49 to 6.28, p = 0.002), use of proton-pump inhibitors (OR 1.64, 95% CI 1.03 to 2.59, p = 0.035), and active smoking (OR 0.37, 95% CI 0.14 to 0.94, p = 0.037). HRPR was associated with increased 6-month mortality rates (3.0% vs 0%; p = 0.016). In conclusion, our findings support the hypothesis that clopidogrel nonresponsiveness is primarily the result of genetic mechanisms and factors that may influence activity of the cytochrome P-450 system.
Available from: Kwang Cha
- "Therefore, it may be seen as a surrogate marker for low responsive-ness. Female gender has been linked to hyporesponsiveness to clo-pidogrel in some reports,9)19) but male gender has also been linked with hyporesponsiveness to clopidogrel by LTA.20) In our report, female gender was related to clopidogrel hyporesponsiveness, but male gender was related to aspirin hyporesponsiveness. "
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ABSTRACT: The aim of this study was to confirm the predictive cut-off values for P2Y12 reaction units (PRU) and aspirin reaction units (ARU) and to evaluate the clinical impact of VerifyNow® assays.
From November 2007 to October 2009, 186 eligible patients were prospectively recruited. Post-treatment platelet reactivity was measured by VerifyNow® assays within 12 to 24 hours after intervention, followed by standard dual maintenance dose therapy for 1 year. All patients had scheduled clinical follow-ups at 1, 3, 6, and 12 months.
The rate of low responders to clopidogrel, aspirin, and both drugs were 41.4%, 10.2%, and 3.8%, respectively. The predictive factors for low responsiveness to clopidogrel (PRU ≥240) were female sex, age, and non-use of cilostazol medication in our univariate analysis and age ≥65 years and non-use cilostazol in the multivariate analysis. The predictors of low responsiveness to aspirin (ARU ≥550) were male sex and age in both univariate and multivariate analyses. There was no significant difference in the clinical event rate with a cut-off value of PRU ≥240 or ARU ≥550 for 30 days and 1-year (p>0.05).
Hyporesponsiveness to antiplatelet agents (namely aspirin and clopidogrel) was identified in about half of the patients. The cut-off point of PRU ≥240 or ARU ≥550 did not confer predictive value for 30-day or 1-year clinical event rates in patients who had undergone coronary intervention with drug-eluting stents.
- "This may be due to the number of cigarettes smoked per day. Previous studies associated smoking ≥10 cigarettes/day with increased clopidogrel-mediated platelet inhibition by LTA and the VerifyNow P2Y12 assay   . However, in this study, we did not assess the exact number of cigarettes/day and therefore we cannot discriminate between patients with ≥10 and b10 cigarettes/day. "
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ABSTRACT: Influencing factors for clopidogrel-mediated platelet inhibition have only been evaluated by one or two different test systems in the same population so far. Since previous studies revealed poor correlations between the various platelet function tests, the identification of influencing variables for clopidogrel response may vary from one test system to the next. We therefore investigated whether the influencing factors for clopidogrel-mediated platelet inhibition depend on the used assay.
Adenosine diphosphate (ADP)-inducible platelet reactivity was assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after angioplasty and stenting for cardiovascular disease. By univariate and multivariate regression analyses, we evaluated the impact of age ≥ 75, gender, body mass index (BMI), diabetes, active smoking, hypertension, hyperlipidemia, C-reactive protein, platelet count, creatinine, use of calcium-channel blockers (CCBs), statins, proton pump inhibitors, beta blockers, angiotensin converting enzyme inhibitors, and angiotensin receptor blockers on clopidogrel-mediated platelet inhibition in each test system.
None of the independent influencing variables was consistent through all test systems. Only by LTA and the VerifyNow P2Y12 assay, age ≥ 75 and the use of CCBs were independently associated with higher on-treatment platelet reactivity. Only by the VASP assay and MEA, on-treatment platelet reactivity increased linearly with BMI. Further, only by MEA, residual ADP-inducible platelet reactivity increased linearly with platelet count, whereas an increase in platelet count was independently associated with a decrease in ADP-inducible platelet activation by the Impact-R.
The influencing factors for platelet reactivity during clopidogrel therapy are assay-dependent.
Available from: Daniel Bur
- "Both concomitant treatment with strong CYP3A4 inhibitors (Suh et al., 2006; Farid et al., 2007; Siller-Matula et al., 2008) as well as a reduced activity of CYP2C19 in patients with CYP2C19 single nucleotide polymorphisms were associated with an impaired pharmacological activity of clopidogrel (Kim et al., 2008; Mega et al., 2009; Simon et al., 2009). Several clinical studies with ex vivo determination of residual platelet aggregation demonstrated that CYP2C19 inhibitors such as proton pump inhibitors (PPIs) decrease the pharmacological effect of clopidogrel (Gilard et al., 2008; O'Donoghue et al., 2009; Price et al., 2009; Zuern et al., 2010). These findings are supported by two retrospective studies with clinical endpoints (death, re-hospitalization and/or re-infarction) (Ho et al., 2009; Juurlink et al., 2009), whereas a third clinical study failed to show an increased cardiovascular risk for patients with concomitant ingestion of clopidogrel and a PPI (O'Donoghue et al., 2009). "
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ABSTRACT: The conversion of clopidogrel to its active metabolite, R-130964, is a two-step cytochrome P450 (CYP)-dependent process. The current investigations were performed to characterize in vitro the effects of different CYP inhibitors on the biotransformation and on the antiplatelet effect of clopidogrel.
Clopidogrel biotransformation was studied using human liver microsomes (HLM) or specific CYPs and platelet aggregation using human platelets activated with ADP.
Experiments using HLM or specific CYPs (3A4, 2C19) revealed that at clopidogrel concentrations >10 microM, CYP3A4 was primarily responsible for clopidogrel biotransformation. At a clopidogrel concentration of 40 microM, ketoconazole showed the strongest inhibitory effect on clopidogrel biotransformation and clopidogrel-associated inhibition of platelet aggregation with IC(50) values of 0.03 +/- 0.07 microM and 0.55 +/- 0.06 microM respectively. Clarithromycin, another CYP3A4 inhibitor, impaired clopidogrel biotransformation and antiplatelet activity almost as effectively as ketoconazole. The CYP3A4 substrates atorvastatin and simvastatin both inhibited clopidogrel biotransformation and antiplatelet activity, less potently than ketoconazole. In contrast, pravastatin showed no inhibitory effect. As clopidogrel itself inhibited CYP2C19 at concentrations >10 microM, the CYP2C19 inhibitor lansozprazole affected clopidogrel biotransformation only at clopidogrel concentrations < or =10 microM. The carboxylate metabolite of clopidogrel was not a CYP substrate and did not affect platelet aggregation.
At clopidogrel concentrations >10 microM, CYP3A4 is mainly responsible for clopidogrel biotransformation, whereas CYP2C19 contributes only at clopidogrel concentrations < or =10 microM. CYP2C19 inhibition by clopidogrel at concentrations >10 microM may explain the conflicting results between in vitro and in vivo investigations regarding drug interactions with clopidogrel.
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