Antiplatelet Efficacy Of Clopidogrel Research Articles

P-glycoprotein deficiency enhances metabolic activation of and platelet response to clopidogrel through marked up-regulation of Cyp3a11 in mice: Direct evidence for the interplay between P-glycoprotein and Cyp3a

Variability in P-glycoprotein (P-gp) efflux transporting activity was supposed to be involved in altered intestinal absorption and bioavailability of clopidogrel in patients; however, reliable evidence is still lacking. In this study, we sought to determine whether P-gp could play an important role in the metabolic activation of and platelet response to clopidogrel in mice. Abcb1a/1b knock-out (KO) and wild-type (WT) mice were used to evaluate differences in the intracellular accumulation of clopidogrel in the intestine, liver, and brain tissues and in systemic exposure of clopidogrel and its main metabolites as well as the mechanisms involved. Results indicated that, compared with WT mice, KO mice exhibited an 84% increase in systemic exposure of clopidogrel active thiol metabolite H4 and a 14.5% rise of suppression of ADP-induced platelet integrin αIIbβ3 activation, paralleled by a 41% decrease in systemic exposure of clopidogrel due to enhanced systemic clearance. Furthermore, KO mice displayed a 45% increase in Cyp3a11 but a 23% decrease in Ces1 at their protein levels compared with WT mice. Concurrently, intracellular clopidogrel concentrations in the tissues examined did not differ significantly between KO and WT mice. We conclude that although P-gp does not transport clopidogrel and its major metabolites in mice, P-gp-deficient mice exhibit elevated formation of the active metabolite H4 and enhanced antiplatelet effect of clopidogrel through up-regulation of Cyp3a11 and down-regulation of Ces1, suggesting that P-gp activity may correlate inversely with the formation of H4 and antiplatelet efficacy of clopidogrel in clinical settings due to P-gp and CYP3A4 interplay.

The Impact of Cytochrome P450 2C19 Polymorphism on Cardiovascular Events in Indonesian Patients with Coronary Artery Disease

Background: The polymorphism of cytochrome P450 2C19 (CYP2C19) has been documented as the determinant variability in the antiplatelet effect of clopidogrel. The relation between CYP2C19 polymorphism and the antiplatelet efficacy of clopidogrel in Indonesian patients with coronary artery disease (CAD) is unknown. To address this issue, we examined the distribution of CYP2C19 genotypes and platelet aggregation, and assessed the impact of CYP2C19 polymorphism on response to clopidogrel and cardiovascular events. Methods: This observational analytic study with prospective cohort approach was conducted in Wahidin Sudirohusodo and Hasanuddin University Hospital, Makassar. We measured the CYP2C19 genotype by polymerase chain reaction-restriction fragment linked polymorphism (PCR-RFLP) method and platelet aggregation by optical platelet aggregometry with 10 μmol of adenosine diphosphate (ADP) in 69 patients with stable CAD who were treated with clopidogrel. Platelet hyperaggregation was defined as maximal platelet aggregation > 94.3%. The patients were followed up every month at the outpatient department for 6 months or at end point. The end point was acute myocardial infarction, ischemic stroke, or cardiovascular death. Results: Distribution of CYP2C19 alleles were 89.8%, 40.6%, and 11.6%, in CYP2C19*1, CYP2C19*2, and CYP2C19*3, respectively. Distribution of CYP2C19 genotype were 50.7%, 29.0%, 8.7%, 8.7%, and 2.9% in CYP2C19*1/*1, *1/*2, *1/*3, *2/*2, and *2/*3, respectively. Platelet hyper aggregation was more in patients with polymorphism than wild type (p 0.034; OR 3.707) and was associated with cardiovascular events (p 0.030; OR 13.250). There was acute myocardial infarction in 2 patients, ischemic stroke in 1 patient, and cardiovascular death in 1 patient. All of these patients were carrying at least one variant allele of CYP2C19; details of genotype were in two patients with CYP2C19*1/*2, one patient with *2/*2, and one with *2/*3 alleles. Conclusion: CYP2C19*2 and *3 were associated with cardiovascular events due to platelet hyper aggregation.

Meta-analysis of effects of ABCB1 polymorphisms on clopidogrel response among patients with coronary artery disease.

The substantial variability in the antiplatelet efficacy of clopidogrel has raised major concerns. Molecular epidemiological research suggests that ABCB1 C3435T polymorphism may be associated with clopidogrel response, but results remain controversial. To derive a more precise evaluation of the associations between ABCB1 C3435T polymorphism and the clinical efficacy of clopidogrel, we have conducted a PRISMA-compliant meta-analysis. The PubMed and EMBASE databases were searched for eligible studies up to 25 October 2016. The odds ratio (OR), the standard mean difference (SMD) and 95% confidence interval (CI) were applied to assess the strength of the relationship. Overall, 28 related studies involving 23,243 patients were analyzed. No association was found between the ABCB1 polymorphisms and the primary outcome. In the subgroup analysis, the C3435T mutation significantly reduced platelet activity as tested by the LTA assay in the dominant (SMD -0.140, 95% CI -0.272 to -0.009, P = 0.036) and heterozygous (SMD -0.154, 95% CI -0.290 to -0.017, P = 0.027) models, but the result lacked robustness in the sensitivity analysis. A significant association between the C3435T polymorphism and bleeding risk was also observed with low heterogeneity in the dominant (OR 1.805, 95% CI1.124-2.900, P =0.015, I 2 = 0%), homozygous (OR 1.952, 95% CI 1.055-3.611, P = 0.033, I 2 = 13.2%) and heterozygous (OR 1.793, 95% CI 1.091-2.946, P = 0.021, I 2 = 0%) models in Asian patients. The results of the meta-analysis suggest that ABCB1 C3435T polymorphism may increase the risk of bleeding in Asian patients treated with clopidogrel. The implied relationship needs to be verified in future basic genetic pharmacology studies.

The Effect of Rabeprazole on the Antiplatelet Efficacy of Clopidogrel: A Systematic Review

Introduction: Clopidogrel is a P2Y12 receptor antagonist given to patients with coronary heart disease, usually in combination with aspirin. It is metabolized to its active component through the cytochrome P450 2C19 (CYP2C19) isoenzyme. Proton pump inhibitors (PPI) are commonly used in patients who are receiving clopidogrel, especially those at high-risk for gastrointestinal bleeding. However, certain PPIs are likewise metabolized through the CYP2C19 isoenzyme. Co-administration of the two classes of drugs may lead to lower levels of clopidogrel, leading to lower antiplatelet efficacy and lower effects on cardiovascular disease prevention of the drug. Objective: To determine the effects of rabeprazole on platelet activity, major adverse cardiovascular outcomes and gastrointestinal bleeding among patients receiving clopidogrel Methodology: We performed this meta-analysis that included all types of studies (randomized controlled trials, case control studies, prospective and retrospective cohort studies) that investigated rabeprazole versus no rabeprazole or placebo. The population consisted of patients who received clopidogrel for any indication with concomitant administration of rabeprazole versus clopidogrel alone. Randomized trials were assessed using Cochrane’s Collaboration tool for assessment of risk of bias. For non randomized studies, Newcastle-Ottawa Quality Assessment Scale for cohort studies was used. Dichotomous data were analyzed using risk ratio and 95% confidence interval, while continuous variables were analyzed using mean differences and standard deviation. Heterogeneity was tested using chi-square test and I2 statistics. Results: There were no statistically significant differences noted in the outcomes of maximal platelet aggregation (mean difference 0.75, 95% CI -3.85 to 5.35), platelet reactivity index (mean difference -0.75, 95% CI -5.11 to 3.61), total cardiovascular events (RR 2.64, 95% CI 0.65 to 10.75) and gastrointestinal bleeding (RR 0.72, 95% CI 0.34 to 1.55) between clopidogrel-treated patients on rabeprazole compared to those without.. Data were not heterogenous, except on the outcome of total cardiovascular events. An influence analysis showed that removal of one trial made the outcome non-heterogenous, but the outcome difference was still not statistically significant (RR 1.25, 95% CI 0.66 to 2.37). Conclusion: Rabeprazole in addition to clopidogrel did not significantly affect maximal platelet aggregation, platelet reactivity index, gastrointestinal bleeding and cardiovascular outcomes.

Effects of Concurrent Calcium Channel Blocker on Antiplatelet Efficacy of Clopidogrel Therapy: A Systematic Review.

Clopidogrel is a widely used drug in clinical practice. Controversy persists as to whether it interacts with proton pump inhibitors. Recently, research interest has grown in the area concerning an interaction of clopidogrel with calcium channel blockers. Multiple studies have been conducted to evaluate the effect of calcium channel blockers on the efficacy of clopidogrel, both in vitro and in vivo. The authors aim to present a systematic review of the published studies in the literature. Various terms were searched in PubMed, Web of Science, and The Cochrane database. Abstracts of studies were read and based on strict exclusion criteria; a study was included/excluded into the review. A total of 424 studies were initially included. Based on exclusion criteria, 22 studies were finally included in the review. Various studies report widely different results regarding the effects of calcium channel blockers on antiplatelet efficacy of clopidogrel. Large prospective studies are needed to delineate the association or lack thereof.

Drug–drug interaction of rabeprazole and clopidogrel in healthy Chinese volunteers

This study was aimed to determine the impact of rabeprazole (RBRZ) on the antiplatelet efficacy of clopidogrel (CPG) in healthy Chinese volunteers, and further to predict the effect of CYP2C19 genetic polymorphism on the efficacy of rabeprazole and clopidogrel. The open-label, two period cross-over study was conducted in 20 healthy Chinese subjects with different CYP2C19 genotypes receiving clopidogrel, rabeprazole or the two drugs, respectively. All the volunteers were divided into two groups, poor metabolizers (PMs) and extensive metabolizers (EMs), depending on CYP2C19 genotypes. Blood samples were collected at baseline and at 0.5, 1, 2, 3, 4, 6, 8, 10, and 12 h after administration. The plasma concentrations of rabeprazole and clopidogrel were analyzed by LC-MS/MS and ADP-induced platelet aggregation was detected by the optical turbidimetric method. There were no significant differences in the mean plasma concentration-time curves of clopidogrel (CPG), the inactive metabolite clopidogrel carboxylic acid (CPG-CA), the active metabolite clopidogrel-MP-Derivative (MP-AM), and rabeprazole (RBRZ) according to the co-administration of CPG and RBRZ. There were no major changes in the pharmacokinetics of CPG and RBRZ. The maximal ADP-induced platelet aggregation (2 μmol/L) was decreased in EMs compared with PMs. Co-administration of rabeprazol and clopidogrel did not affect the antiplatelet efficacy of clopidogrel. The CYP2C19 genetic polymorphism may impact the efficacy of clopidogrel.

Effects of Proton Pump Inhibitors on Platelet Function in Patients Receiving Clopidogrel

There is considerable debate regarding the negative impact of concomitant proton pump inhibitor (PPI) therapy on the antiplatelet efficacy of clopidogrel. The aim of this study was to perform a systematic review of studies that have evaluated the platelet function of patients receiving clopidogrel alone compared with those receiving both clopidogrel and PPIs. We searched MEDLINE, EMBASE and the Cochrane Controlled Trials Register in February 2011 for randomized and non-randomized studies that reported platelet function results in patients taking clopidogrel, with or without PPIs. Our review included 19 studies (13 trials and 6 observational studies) involving 4693 patients. There was considerable heterogeneity in the study designs, patient characteristics, laboratory tests of platelet function, and drug exposure (dose and duration of PPI and clopidogrel). There was some evidence against omeprazole, with five of nine studies demonstrating a significant interaction with clopidogrel. The available platelet function data on esomeprazole (six studies) or pantoprazole (six studies) did not demonstrate a significant interaction. Of the six studies that statistically analysed platelet function data with omeprazole compared with pantoprazole, three showed a significantly greater interaction between omeprazole and clopidogrel, whereas three studies with limited sample sizes were unable to find a significant difference in the effects of omeprazole and pantoprazole. Platelet function studies do not demonstrate a clear or consistent interaction between clopidogrel and PPIs. These studies are difficult to interpret given the lack of information on drug exposure (dose and duration), variation in laboratory methodology and lack of genetic information. Consequently, platelet function data are of uncertain clinical relevance in determining the risk of an adverse cardiovascular interaction between PPIs and clopidogrel. Clinicians should continue to clinically assess the gastrointestinal risk of the patients and make their prescribing decision for PPIs based on any anticipated benefits in reducing risk of peptic ulcers and gastrointestinal haemorrhage.

No Association of ABCB1 C3435T Genotype With Clopidogrel Response or Risk of Stent Thrombosis in Patients Undergoing Coronary Stenting

The prodrug clopidogrel requires intestinal absorption by the efflux pump P-glycoprotein MDR1 (multidrug resistant-1), encoded by the ABCB1 gene. Prior studies suggested that a common and functional genetic variant (C3435T, rs1045642) within ABCB1 influences clopidogrel treatment efficacy; however, existing data are highly inconsistent, because other studies failed to replicate this postulated association. Thus, the aim of this study was to assess the association of ABCB1 C3435T genotypes with the antiplatelet efficacy of clopidogrel and the risk of stent thrombosis (ST) in large cohorts of clopidogrel-treated patients undergoing percutaneous coronary intervention. DNA samples from 1524 clopidogrel-treated patients undergoing percutaneous coronary intervention were genotyped for ABCB1 C3435T, and ADP-induced platelet aggregation was assessed in whole blood on a Multiplate analyzer. The clinical impact of the genetic variant was investigated by comparison of genotype frequencies in a registry of 66 cases with definite drug-eluting stent ST versus an ST-free control cohort (n=1408). Platelet aggregation values were similar across ABCB1 C3435T genotypes (P=0.73). No significant influence of ABCB1 C3435T genotypes on the occurrence of ST was found when ST case subjects were compared with control subjects (P=0.89). ABCB1 C3435T genotypes did not influence the antiplatelet response to clopidogrel or the risk of ST in clopidogrel-treated patients undergoing percutaneous coronary intervention. Routine genotyping of ABCB1 C3435T polymorphisms should not be recommended for risk stratification in clopidogrel-treated patients undergoing percutaneous coronary intervention who are similar to those evaluated in the present study.

Impact of proton pump inhibitors on efficacy of clopidogrel: Review of evidence

Clopidogrel is a prodrug which requires cytochrome P450 2C19 (CYP 2C19) enzyme for its conversion to an active thiol metabolite. Proton pump inhibitors (PPIs) inhibits enzyme CYP 2C19 interfering with the conversion of clopidogrel into its active metabolite. Studies document the possible interaction of clopidogrel and PPIs leading to a decrease in the antiplatelet efficacy of clopidogrel. A PubMed/MEDLINE database literature search was carried out and the bibliographies of found articles were checked for other relevant literature. Most retrospective cohort studies and studies using platelet markers found a significant association between PPI use especially omeprazole and decreased efficacy of clopidogrel while few comparative trials using clinical outcomes found no association between the same. Pantoprazole was not associated with the decrease in the antiplatelet efficacy of clopidogrel. Patients on dual antiplatelet therapy and/or with a history of gastrointestinal bleed will require gastroprotection in the form of PPIs. In such cases, pantoprazole should be the preferred PPI. Rabeprazole can be used as an alternative.

13C]Pantoprazole breath test as a predictor of the anti-platelet function of clopidogrel

Clopidogrel, a platelet inhibitor, is metabolized by cytochrome P450 2C19 (CYP2C19) to its active metabolite and, consequently, its anti-platelet efficacy is influenced by CYP2C19 activity. The aim of this study was to determine whether the [(13)C]pantoprazole breath test, a recently developed tool used to measure CYP2C19 activity, can predict the anti-platelet efficacy of clopidogrel. Seventy healthy volunteers with different CYP2C19 genotypes received 100 mg of [(13)C]pantoprazole. Breath samples were collected at 10-min intervals for 60 min, and changes in the carbon isotope ratios ((13)CO(2)/(12)CO(2)) from the baseline level were measured and expressed as a delta-over-baseline (DOB) ratio (per thousand). After a washout period of > 2 weeks, the subjects underwent a platelet aggregation test before and after dosing with 75 mg of clopidogrel for 7 days. The percentage inhibition of platelet aggregation (IPA, %) was then calculated. There was a statistically significant correlation between the area under the curve (AUC)(20-60 min) of the DOB and IPA at 4 h attained by clopidogrel. The mean AUC(20-60 min) of the DOB of the "low-responder" (IPA < 20%) group was significantly lower than that of the responder group (IPA > or = 20%). The results of our preliminary study suggest that the [(13)C]pantoprazole breath test can predict the anti-platelet efficacy of clopidogrel.

Clopidogrel Resistance in Japanese Patients Scheduled forPercutaneous Coronary Intervention

Dual antiplatelet therapy with acetylsalicylic acid (ASA) and a P2Y(12) ADP-receptor blocker is standard for prevention of coronary stent thrombosis. Clopidogrel, a 2(nd)-generation P2Y(12) blocker, has recently become available in Japan and this study aimed to evaluate its antiplatelet effects in Japanese patients. Thirty Japanese patients scheduled for elective coronary stent implantation were enrolled. Under low-dose ASA therapy, 300 mg clopidogrel was loaded on the 1(st) day and a daily 75-mg dose was administered on the following days. Assessed by optical aggregometer, rapid inhibition occurred at 4 h, when the inhibition of platelet aggregation rate (IPA) was 16.4+/-12.8% using 5 mumol/L ADP as the stimulus. The antiplatelet efficacy of clopidogrel was reasonably constant in each patient throughout the study period, although there was a broad inter-individual variation. At 48 h after clopidogrel loading, the ratios of responders (IPA > or =30%), hypo-responders (10%< or =IPA<30%), and non-responders (IPA <10%) were 36%, 50%, and 14%, respectively. The antiplatelet effectiveness of clopidogrel appeared individual-specific with wide inter-individual variation. The rate of clopidogrel non-responders was 14% among the examined Japanese patients.

Abstract 455: Peri-interventional Antiplatelet Effect of Clopidogrel in Patients Undergoing Percutaneous Coronary Intervention is Attenuated by Cytochrome P450 2C19*2 Polymorphism

The thienopyridine derivative clopidogrel is an inactive pro-drug requiring biotransformation by cytochrome P450 isoenzymes (CYP) in order to generate an active metabolite. This metabolite inhibits irreversibly the platelet P2Y12 receptor, thereby exerting the antiplatelet effect of the drug. The EXCELSIOR study showed a 7-fold 30-day risk of major adverse cardiac events in patients with inadequate peri-interventional platelet response to loading with clopidogrel 600 mg. Studies in healthy volunteers on the impact of the CYP2C19 genotype to the interindividual variability in antiplatelet effect of clopidogrel showed conflicting results. The EXCELSIOR study enrolled 802 patients undergoing elective percutaneous coronary intervention (PCI) with stent implantation. The antiplatelet effect of a loading dose of clopidogrel 600 mg was determined by optical aggregometry (5μM ADP) before administration of clopidogrel, at the time of PCI and pre-discharge at day 1after PCI. CYP2C19 genotype (681G&gt;A) was analyzed in 697 patients by real-time PCR. Antiplatelet efficacy of clopidogrel was determined for the different genotypes. Within the subset of the EXCELSIOR cohort, 485 patients (69.6%) were CYP2C19 wild-type homozygous (*1/*1), 199 (28.6%) were CYP2C19*1/*2 and 13 (1.9%) were CYP2C19*2/*2 carrying two allelic variants encoding a deficient CYP2C19 enzyme. Residual platelet aggregation (median; interquartile ranges) determined 5 minutes after addition of ADP 5μM is summarized in relation to the CYP2C19 genotypes in the Table below. These results indicate that the antiplatelet response to a loading dose of clopidogrel 600 mg is substantially attenuated in patients carrying at least one CYP2C19*2 allele. It seems that the CYP2C19 genotype is a major factor contributing to the observed variability in the antiplatelet effect of clopidogrel and might therefore affect clinical outcome of patients undergoing PCI. Relationship Between Genotype and ADP-induced Platelet Aggregation (%)