Influence of cytochrome 2C19 allelic variants on on-treatment platelet reactivity evaluated by five different platelet function tests

Background

The antiplatelet effect of clopidogrel has been linked to cytochrome P450 2C19 (CYP2C19) carrier status. The presence of loss of function and gain of function variants were found to have a gene-dose effect on clopidogrel metabolism. However, genotyping is only one aspect of predicting response to clopidogrel and several platelet function tests are available to measure platelet response.Patients and methodsWe studied the influence of CYP2C19 allelic variants on on-treatment platelet reactivity as assessed by light transmission aggregometry (LTA), the VerifyNow P2Y12 assay, the VASP assay, multiple electrode aggregometry (MEA), and the Impact-R in 288 patients after stenting for cardiovascular disease. Allelic variants of CYP2C19 were determined with the Infiniti® CYP450 2C19 + assay and categorized into four metabolizer states (ultrarapid, extensive, intermediate, poor).

Results

Platelet reactivity increased linearly from ultrarapid to poor metabolizers using the VerifyNow P2Y12 assay (P = 0.04), the VASP assay (P = 0.02) and the Impact-R (P = 0.04). The proportion of patients with high on-treatment residual platelet reactivity (HRPR) identified by LTA, the VerifyNow P2Y12 assay and the VASP assay increased when the metabolizer status decreased, while no such relationship could be identified for results of MEA and Impact-R. The presence of loss of function variants (*2/*2, *2-8*/wt, *2/*17) was an independent predictor of HRPR in LTA and the VASP assay while it did not reach statistical significance in the VerifyNow P2Y12 assay, MEA, and the Impact-R.

Conclusion

Depending on the type of platelet function test differences in the association of on-treatment platelet reactivity with CYP2C19 carrier status are observed.     

CYP2C19*2 and other genetic variants affecting platelet response to clopidogrel in patients undergoing percutaneous coronary intervention

Introduction

Information regarding any possible additional effect of genetic variants other than CYP2C19*2 on platelet reactivity in patients undergoing percutaneous coronary intervention (PCI), while on dual antiplatelet therapy, is sparse.

Materials and Methods

Genotyping for CYP2C19*2, CYP2C19*17, CYP2C9*3, CYP2B6*5, ABCB1 and P2RY12 (c.-217 + 2739 T > C) variants was performed in 146 consecutive PCI patients receiving clopidogrel. Platelet reactivity was assessed by the Verify Now P2Y12 point-of-care assay and high on-treatment platelet reactivity (HTPR) was defined as a Platelet Reactivity Unit (PRU) ≥ 235.

Results

We identified 65(44.5%) patients with HTPR and 38(26%) carriers of at least one CYP2C19*2 allele, which had higher platelet reactivity compared to non-carriers [least square (LS) mean difference 44.5, 95%CI 15.8-77.3, p = 0.003]. In the entire study population, the presence of at least one CYP2C19*2 or P2RY12 allelic variant was independently associated with HTPR (OR = 3.02, 95%CI 1.16-7.86, p = 0.023 and OR = 3.11, 95%CI 1.03-9.39, p = 0.05 respectively). In CYP2C19*2 non-carriers, carriers of at least one CYP2B6*5 allelic variant had higher platelet reactivity compared to the remainders (LS mean difference 35.6, 95%CI 3.7-67.6, p = 0.03) and the presence of at least one CYP2B6*5 or P2RY12 allelic variant was independently associated with HTPR (OR = 3.26, 95%CI 1.08-9.86, p = 0.04 and OR = 4.27, 95%CI 1.11-16.4, p = 0.04 respectively).

Conclusions

Apart from the CYP2C19*2, other genetic variants involved in clopidogrel metabolism and action like CYP2B6*5 and P2RY12 seem to have an important association with HTPR.     

Pharmacodynamic assessment of a novel P2Y12 receptor antagonist in Japanese patients with coronary artery disease undergoing elective percutaneous coronary intervention

Introduction

Numerous reports have shown that prasugrel shows a rapid and consistent antiplatelet effect among European and US patients. Previous studies suggest that prasugrel might be expected to achieve an adequate antiplatelet effect in healthy Asian subjects, even at lower doses than those assessed in the TRITON-TIMI 38 study. In this study, the antiplatelet effect of prasugrel was evaluated in Japanese coronary artery disease (CAD) patients undergoing percutaneous coronary intervention (PCI).

Methods and results

Eighty-four patients were randomized into four treatment groups: prasugrel 10/2.5 mg (loading dose [LD]/maintenance dose [MD]), 15/3.75 mg or 20/5 mg, and clopidogrel 300/75 mg. The LD of each regimen was administered the day before PCI, followed by 28-day MD on aspirin background therapy (81-100 mg). Antiplatelet effects were evaluated by light transmission aggregometry and VASP assay.The mean inhibition of platelet aggregation (IPA) induced by 20 μM of adenosine diphosphate at 4 hours after LD was higher among the prasugrel 10/2.5 mg, 15/3.75 mg and 20/5 mg groups compared with the clopidogrel group (12.3%, 20.9%, 29.8% vs. 8.4%, respectively). The proportion of subjects with an IPA of < 10% on Day 28 was lower among the prasugrel 15/3.75 mg, and 20/5 mg groups than in the clopidogrel group (0%, 6.3% vs. 15.8%, respectively). No “major” or “clinically relevant non-major” bleeding was observed.

Conclusions

Prasugrel 15 mg LD/3.75 mg MD or higher doses was well tolerated and achieved a more rapid, higher and consistent antiplatelet effect than clopidogrel in Japanese CAD patients undergoing PCI.     

The cytochrome 2C19*2 and *3 alleles attenuate response to clopidogrel similarly in East Asian patients undergoing elective percutaneous coronary intervention

Introduction

Carriage of CYP2C19*2 allele is associated with diminished platelet response to clopidogrel. However, the loss-of-function impact of CYP2C19*3 allele on antiplatelet effect of clopidogrel has not been definitely verified. We conducted this study to compare decreased response to clopidogrel according to carriage of CYP2C19*2 vs. *3 allele.

Materials and methods

The study included 190 consecutive Korean patients undergoing elective percutaneous coronary intervention. Light transmittance aggregometry and the VerifyNow P2Y₁₂ assay were used to assess platelet reactivity (PR) at least 12 hours after 300-mg loading of clopidogrel. The cutoff of high on-treatment PR (HPR) was defined as 5 μmol/L ADP-induced PR > 50%. CYP2C19 genotype was analyzed by the SNaPshot method.

Results

Carriers of at least one CYP2C19 variant allele were 115 patients (60.5%), and allelic frequency of CYP2C19*2 and *3 was 30.3% and 6.8%, respectively. PR and the rate of HPR increased proportionally according to the number of CYP2C19 variant allele. Carriage of CYP2C19 variant allele was an only independent predictor of HPR in multivariate analysis. When we compare the effect of allelic carriage, there were no significant differences in platelet measures and the rate of HPR between carriers of CYP2C19*2 and/or *3 allele(s) whether they were intermediate or poor metabolizers.

Conclusion

Carriage of CYP2C19*3 allele is associated with diminished antiplatelet effect of clopidogrel, which may be as potent as the loss-of-function effect of CYP2C19*2 allele.     

Impact of the proton pump inhibitors and CYP2C19*2 polymorphism on platelet response to clopidogrel as assessed by four platelet function assays

Background

Previous studies suggested a possible negative interference of proton pump inhibitors (PPIs) on clopidogrel’s antiplatelet effect because of the competitive inhibition of the CYP 2C19 isoenzyme. Moreover, carriers of the loss-of-function allele of CYP2C19 polymorphism (CYP2C19*2) display significantly lower responses to clopidogrel. In this study, we investigated the association between CYP2C19*2 genotype, PPI intake and clopidogrel resistance in patients with coronary artery disease (CAD) and their effect on clinical outcome.

Methods

We recruited 95 patients with CAD receiving chronic clopidogrel therapy in combination with aspirin. Platelet reactivity was simultaneously assessed by INNOVANCE PFA-100 P2Y, ADP-induced light transmission aggregometry (LTA), flow-cytometric vasodilator-stimulated phosphoprotein (VASP)-phosphorylation assay and multiple electrode aggregometry (Multiplate). Cardiovascular outcomes were recorded during 1-year follow-up period.

Results

Only platelet reactivity assessed by measuring platelet phosphorylated-VASP demonstrated a significant higher platelet reactivity in carriers of CYP2C19*2 (p = 0.023). The other methods displayed higher - but not statistically significant - platelet reactivity in patients carrying the CYP2C19*2 variant as compared with non-carriers. Patients on PPIs demonstrated almost similar suppression of platelet reactivity in comparison with those not treated with PPIs by all platelet function assays. In logistic regression analysis none of the platelet function assays measurements were related with clinical outcomes. Similarly neither CYP2C19*2 genetic variant nor PPI treatment were associated with adverse clinical events.

Conclusions

PPI co-administration did not influence clopidogrel’s antiplatelet effect on laboratory testing by all platelet function assays used. On the contrary, patients carrying CYP2C19*2 genotype had significantly higher residual platelet reactivity as estimated by VASP-phosphorylation assay.     

Platelet reactivity evaluated with the VASP assay following ticagrelor loading dose in acute coronary syndrome patients undergoing percutaneous coronary intervention

Background

The level of platelet reactivity (PR) inhibition obtained after P2Y12-ADP receptor antagonist loading dose (LD) is associated with the ischemic and bleeding risk following percutaneous coronary intervention (PCI) in acute coronary syndromes (ACS).

Objective

We aimed to evaluate the level of PR inhibition achieved by a 180 mg LD of ticagrelor and the rate of high on-treatment platelet reactivity (HTPR) in ACS patients undergoing PCI.

Methods

We performed a multicentre prospective observational study enrolling ACS patients undergoing PCI. Patients were included if they were admitted for ST-elevation myocardial infarction or non ST-elevation ACS. To assess PR, a VASP index was measured at least 6 and within 24 hours following a 180 mg LD of ticagrelor. HTPR was defined as a VASP index ≥ 50%.

Results

One hundred and fifteen patients were included: 31.3% of STEMI, 49.6% of NSTEMI and 19.1% of unstable angina. Following ticagrelor LD the mean VASP index was 17 ± 14%. However the response to ticagrelor was not uniform with a small inter-individual variability: inter quartile range: 7.6–22.8% and a rate of HTPR of 3.5%. A high number of patients, 65.6%, had a VASP index < 16%. None of the baseline characteristics of the study population was associated with PR. In addition, PR was similar in STEMI, NSTEMI and unstable angina (p = 0.9).

Conclusion

In ACS patients the level of PR inhibition achieved by a 180 mg loading dose of ticagrelor is not uniform and the rate of HTPR is 3.5%. A high proportion of patients exhibited a VASP index < 16%.     

Sustained enhancement of residual platelet reactivity after coronary stenting in patients with myocardial infarction compared to elective patients

Introduction

Elevated platelet reactivity despite antiplatelet therapy is associated with an increased cardiovascular risk after percutaneous coronary interventions. Current guidelines recommend uniform antiplatelet maintenance regimen after percutaneous coronary interventions for patients with myocardial infarction and elective patients. We sought to demonstrate that there is a persistent enhancement of residual platelet reactivity after myocardial infarction, requiring an intensified antiplatelet maintenance therapy.

Materials and Methods

A total of 66 patients after coronary stenting for myocardial infarction (n = 36) or elective coronary stenting (n = 30) were included in this prospective, controlled study. Platelet reactivity to adenosine-5-diphosphate and arachidonic acid under treatment with clopidogrel (75 mg) and acetyl salicylic acid (100 mg) were assessed 48 hours and 30 days after coronary stenting using light transmission aggregometry and multiple electrode platelet aggregometry (Multiplate analyzer) simultaneously.

Results

Fourty-eight hours after coronary stenting all measures of residual platelet reactivity were significantly elevated in the infarction group. After a mean follow up of 37 days, residual platelet reactivity to adenosine-5-diphosphate was still consistently elevated, albeit statistically not significant. Contrarily, residual platelet reactivity to arachidonic acid significantly decreased and returned to normal by the time of follow up. Regression analyses revealed myocardial infarction, C-reactive protein and fibrinogen as predictors of enhanced platelet reactivity 48 hours after coronary stenting.

Conclusions

Patients undergoing coronary stenting for acute myocardial infarction exhibit an enhancement of residual platelet reactivity sustaining for at least 48 hours following coronary stenting. This finding provides a rationale for a continued intensified antiplatelet therapy after myocardial infarction.     

The influencing factors for clopidogrel-mediated platelet inhibition are assay-dependent

Background

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.

Patients and methods

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.

Results

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.

Conclusion

The influencing factors for platelet reactivity during clopidogrel therapy are assay-dependent.     

Influence of platelet reactivity and response to clopidogrel on myocardial damage following percutaneous coronary intervention in patients with non-st-segment elevation acute coronary syndrome

Introduction

A wide variability in the response to clopidogrel and magnitude of post-treatment platelet reactivity has been described. However, this has been demonstrated by light transmittance aggregometry, a method too laborious for daily practice. Point-of-care devices may overcome this limitation, but little is known on the predictive value of such measurements. Our objective was to determine the relationship between platelet reactivity and the incidence of myocardial damage following percutaneous coronary intervention (PCI) in patients with Non-ST-segment Elevation Acute Coronary Syndrome (NSTEACS).

Materials and Methods

This prospective study included 93 patients with NSTEACS and PCI. All patients received a loading dose of 300 mg of clopidogrel and 250 mg of aspirin. Myocardial damage was defined as any elevation above upper limit of normal or previous levels of troponin T, assessed every 6 h for at least 24 h following PCI. Platelet reactivity not related to clopidogrel (BASE reactivity), related to P2Y12 inhibition (P2Y12 reactivity) and inhibition of platelet aggregation (IPA) were assessed immediately pre-PCI with the VerifyNow® device.

Results

Myocardial damage was detected in 60 patients (64.5%). Higher BASE reactivity was associated with myocardial damage (287.8 ± 62.6 vs. 260 ± 55.9 units, p = 0.043) while a trend was found for P2Y12 reactivity (173.4 ± 70.3 vs. 149.2 ± 58.4 units, p = 0.109). No relationship was detected for IPA. Multivariate logistic regression analysis confirmed that BASE reactivity (p = 0.04) and P2Y12 reactivity (p = 0.03) were independent predictors of myocardial damage.

Conclusions

Platelet reactivity before PCI appears to be better predictor of myocardial damage than does response to clopidogrel.     

Paraoxonase-1 activity affects the clopidogrel response in CYP2C19 loss-of-function carriers

Background

The impact of paraoxonase-1 (PON1) activity on the response to clopidogrel may differ in patients treated with drug-eluting stents (DES) in association with CYP2C19 loss-of-function (LOF) polymorphisms.

Methods

This study included 112 Japanese patients receiving clopidogrel (75 mg/day) and aspirin (100 mg/day) who underwent optical coherence tomography (OCT) examination 9 months after DES implantation. The CYP2C19 genotype was analyzed and LOF carriers (*1/*2, *1/*3, *2/*2, *3/*3, *2/*3) were identified. At the 9-month follow-up, platelet reactivity was determined by measuring the P2Y12 reactivity unit (PRU) using a VerifyNow P2Y12 assay, PON1 activity was evaluated and intra-stent thrombus was evaluated by OCT.

Results

Of the 112 Japanese patients, 75 were LOF carriers (67.0%). The patients were divided into tertiles according to the PON1 activity (tertile 1; < 230 U/L, tertile 2; 230–283 U/L, tertile 3; > 283 U/L). In the VerifyNowP2Y12 analysis, tertile 1 had a higher PRU than tertiles 2 and 3 in LOF carriers, and there was no difference among tertiles in non-carriers. The highest incidence of intra-stent thrombus was observed in tertile 1 followed by tertiles 2 and 3 in LOF carriers, whereas there was no such difference in non-carriers. Multivariate analysis revealed that LOF carriers and PON1 activity tertile 1 were independent predictors of intra-stent thrombus in all patients. In LOF carriers, tertile 1 was the only independent predictor for intra-stent thrombus.

Conclusion

Low PON1 activity is associated with a low response to clopidogrel and a high frequency of intra-stent thrombus only in LOF carriers.     

Genetic and non-genetic factors responsible for antiplatelet effects of clopidogrel in Japanese patients undergoing coronary stent implantation: An algorithm to predict on-clopidogrel platelet reactivity

Introduction

Antiplatelet effects of clopidogrel appear to be affected by various factors including genetic polymorphism. So far, there has been little information about the response of clopidogrel in Asians, whose prevalence of a CYP2C19 loss-of-function (LOF) allele is high.

Methods and Results

We investigated background and clinical factors affecting on-clopidogrel platelet reactivity in Japanese patients undergoing coronary stent implantation (n = 114). In univariate analysis, antiplatelet effects of clopidogrel in a steady state were associated with not only CYP2C19 genotypes but also several factors including dyslipidemia. In addition, we developed an algorithm that can estimate P2Y12 Reaction Units (PRU) in a steady state by multiple regression analysis and evaluated the adequacy of the algorithm by the Akaike Information Criterion.

Conclusions

We revealed several factors influencing on-clopidogrel platelet reactivity in Japanese patients. We also succeeded in developing an algorithm that estimates PRU in a steady state, although it is uncertain whether the algorithm can be applied to other populations.     

Pharmacodynamics and pharmacokinetics of the platelet GPIIb/IIIa inhibitor tirofiban in patients undergoing percutaneous coronary intervention: implications for adjustment of tirofiban and clopidogrel dosage

INTRODUCTION: Despite extensive data supporting the use of platelet glycoprotein (GP) IIb/IIIa (GPIIb/IIIa) inhibitors in the therapy of patients with acute coronary syndromes (ACS), there is considerable debate as to the optimal choice of antiplatelet regimen. The objective of this study was to conduct a detailed time-resolved analysis of the effects of the GPIIb/IIIa inhibitor tirofiban with concomitant clopidogrel in ACS patients undergoing percutaneous coronary intervention (PCI) to improve the dosing regimen of these two commonly used antiplatelet drugs. METHODS: The study was performed in 14 patients with non-ST-segment elevation (NSTE) ACS who underwent PCI while being treated with the current typically utilized regimen of tirofiban (10 microg/kg bolus, 0.15 microg/kg/min infusion) and clopidogrel (300 mg). Platelet function was assessed before, during, and after tirofiban infusion using a panel of agonists for ADP receptors, PAR1 and PAR4 thrombin receptors, and collagen receptors. RESULTS: Measurements of circulating tirofiban levels demonstrated a trough, which paralleled a reduction in platelet inhibition for all platelet agonists during the time when PCI was being performed. Interestingly, younger ACS patients (<55 years) exhibited less inhibition of platelet function both during the PCI procedure and after termination of the tirofiban infusion. These apparent age differences were primarily attributed to a decreased responsiveness of the younger patients to clopidogrel. CONCLUSIONS: This study shows that the currently utilized tirofiban dosage is suboptimal and suggests that patients may benefit from a higher dose regimen.     

Variable responsiveness to clopidogrel and aspirin among patients with acute coronary syndrome as assessed by platelet function tests

Unresponsiveness to clopidogrel or aspirin has been reported in patients with acute coronary syndrome (ACS). Platelet aggregometry (PA) and the Impact-R [Cone and Plate(let) Analyzer (CPA) technology, measuring whole blood platelet adhesion under flow conditions] were compared in detecting laboratory unresponsiveness to clopidogrel and aspirin among ACS patients. Platelet-rich plasma (PRP) samples were evaluated in 404 patients by PA using adenosine diphosphate (ADP) and arachidonic acid (AA) and whole blood samples by the Impact-R ADP- and AA-response tests. The first cohort (n=114) was assayed by PA on days 1 and 4 of the onset of ACS. A patient with relative decrease of /=70%. A patient with an absolute value of AA-induced maximal aggregation >/=60% was defined as laboratory NR patient to aspirin. The second cohort (n=290) was tested on day 4 by both systems and results analyzed by receiver operating characteristic curve. The following cut-off values of the Impact-R surface coverage were obtained: 相似文献   

Response to antiplatelet therapy is independent of endogenous thrombin generation potential

Background

Thrombin is the most potent platelet activator, and achieves rapid platelet activation even in the presence of antiplatelet therapy. Since activated platelets respond stronger to additional stimuli, the extent of endogenous thrombin generation may in part be responsible for the reported response variability to aspirin and clopidogrel therapy.

Patients and methods

Thrombin generation potential was measured with a commercially available assay, and platelet reactivity was assessed with the vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, light transmission aggregometry (LTA), the VerifyNow aspirin and P2Y12 assays, and multiple electrode aggregometry (MEA) in 316 patients on dual antiplatelet therapy undergoing angioplasty and stenting.

Results

Peak thrombin, the lag phase and the area under the curve of thrombin generation correlated poorly with on-treatment platelet reactivity by all test systems. High on-treatment residual platelet reactivity (HRPR) in response to arachidonic acid was seen in 33 (10.5%), 41 (13%), and 79 (25.7%) patients by LTA, the VerifyNow aspirin assay, and MEA, respectively. HRPR in response to adenosine diphosphate was seen in 150 (48.1%), 48 (15.3%), 106 (33.7%), and 118 (38.3%) patients by the VASP assay, LTA, the VerifyNow P2Y12 assay, and MEA, respectively. Peak thrombin generation did not differ between patients without and with HRPR by the VASP assay, LTA, the VerifyNow P2Y12 assay and MEA. In the VerifyNow aspirin assay, patients without HRPR had higher peak thrombin generation than patients with HRPR (p = 0.01). Finally, patients without and with high peak thrombin generation exhibited similar on-treatment platelet reactivity by all test systems, and high peak thrombin generation occurred to a similar extent in patients without and with HRPR.

Conclusion

Response to antiplatelet therapy with aspirin and clopidogrel is not associated with thrombin generation potential.     

Pharmacogenomics of clopidogrel: evidence and perspectives

Clopidogrel has become the mainstay oral antiplatelet regimen to prevent recurrent ischemic events after acute coronary syndromes or stent placement. However, there is marked interindividual variability in the antiplatelet effects of clopidogrel, and a reduced response to this drug may be a risk factor for ischemic complications. Pharmacogenomic analyses, including candidate-gene and genome-wide association studies, have confirmed that genetic polymorphisms in the hepatic cytochrome P450 (CYP) 2C19 dominantly affect the antiplatelet effects of clopidogrel. CYP2C19 reduced-function alleles have been associated with a significant decrease in clopidogrel responsiveness and a higher risk of adverse cardiac events including stent thrombosis, myocardial infarction, and death in several prospective studies, although these effects were not reproduced in a recent large randomized study that included a randomized control group. The US Food and Drug Administration addressed this issue by adding a boxed warning to the clopidogrel label and suggesting that adjusting the clopidogrel dose or using alternative antiplatelet agents should be potentially implemented for high-risk individuals who are identified based on the CYP2C19 genotype. Although it is promising that CYP2C19 genotyping could be used to guide personalized antiplatelet clopidogrel therapy, currently there is insufficient evidence to recommend routine genetic testing. Prospective randomized clinical trials are necessary to validate this pharmacogenomic approach to clopidogrel therapy. In the most recent trial, paraoxonase-1 (PON1) was identified as a crucial new enzyme for clopidogrel bioactivation, with its common Q192R polymorphism determining the rate of active metabolite and the clinical activity of clopidogrel. Further studies are needed to investigate the comprehensive influence of a number of different polymorphisms of CYP2C19 and PON1 variant alleles or other genetic variants on clopidogrel in various ethnic populations.     

The effect of clopidogrel besylate and clopidogrel hydrogensulfate on platelet aggregation in patients with coronary artery disease: a retrospective study

Background

Recently several alternative forms of the original clopidogrel hydrogensulfate (CHS) were spread worldwide. A large amount of such drugs turned out to be clopidogrel besylate (CB). Only three studies, involving healthy volunteers, investigated the antiplatelet effect of CB, whereas its attribute remained unexplored in the case of patients with cardiovascular diseases. This retrospective study aimed to evaluate the difference between the antiplatelet effects of two clopidogrel formulas, CHS and CB, on patients with coronary artery diseases.

Methods

Data of 150 patients with previous CHS treatment were investigated. According to the documentations, the CHS therapy was shifted to CB. 94 patients of the selected population received dual antiplatelet therapy, clopidogrel and aspirin. The antiplatelet effects of CHS and CB were compared by ADP induced platelet aggregation measurements using light transmission aggregometry.

Results

Irrespective of the therapeutic combinations the performed statistical investigations failed to show significant difference (p = 0.30) between the effect of CB (AGGmax_CB: 27.6 ± 13.7%) or CHS (AGGmax_CHS: 29.0 ± 15.3%) on the ADP induced platelet aggregation. Insignificant deviations were found in both forms of clopidogrel salts, either in the lack (AGGmax_CB : 32.5 ± 14,2%; AGGmax_CHS: 34,0 ± 16,1%; p = 0,29) or in the presence of aspirin (AGGmax_CB: 24.7 ± 12,5%; AGGmax_CHS: 26,0 ± 14,1%; p = 0,31).

Conclusion

Our results indicated that both CB and CHS had an identical inhibitory effect on ADP induced platelet aggregation in patients with cardiovascular diseases. Moreover their efficiency showed no overall significant difference in the case of dual antiplatelet therapy with aspirin as well. However there might be an inter- and intraindividual variability between the two clopidogrel formulas.     

Effects of additional treatment of sarpogrelate to aspirin therapy on platelet aggregation and plasma plasminogen activator inhibitor activity in patients with stable effort angina

Introduction

Serotonin is secreted from platelets at sites of endothelial injury, where it promotes thrombogenic reactions. Serotonin is reported to be associated with not only coronary artery disease but also cardiac events.

Materials and Methods

We studied 33 patients with stable effort angina (SEA) (11 patients with multivessel disease (MVD) and 22 patients with singlevessel disease (SVD)) and 25 patients with chest pain syndrome (CPS). Sarpogrelate was administered to 22 of 33 patients with SEA in addition to aspirin therapy, and platelet aggregation, plasma serotonin concentration, and plasma plasminogen activator inhibitor (PAI) activity were measured before and 1 week after administration.

Results and Conclusions

Serotonin level was higher in patients with MVD than in those with SVD (p < 0.05) and in those with CPS (p < 0.001). The formation of small-sized platelet aggregates was significantly higher in the high serotonin group than in the low serotonin group of SEA patients. The formation of large-sized platelet aggregates was significantly decreased by administration of sarpogrelate (P < 0.05). The formation of small- or medium-sized aggregates was not significantly decreased. Plasma PAI activity decreased significantly (P < 0.05) although the plasma serotonin concentration did not show significant change by administration of sarpogrelate. Plasma serotonin level is increased in relation to severity of coronary artery disease and plasma serotonin level is associated with increased platelet aggregation. Administration of sarpogrelate in addition to aspirin therapy reduces the increased platelet aggregation and PAI activity, and it may indicate that additional administration of sarpogrelate is useful for patients with SEA.     

Impact of CYP2C19 Polymorphism and Proton Pump Inhibitors on Platelet Reactivity to Clopidogrel and Clinical Outcomes Following Stent Implantation

Background

The response to clopidogrel, and some kind of the drug interaction are multifactorial.

Methods and Results

We enrolled 174 consecutive patients and determined CYP2C19 genotypes, measured platelet aggregation, and assessed the relationship between CYP2C19 genotype and platelet reactivity 24 hours after clopidogrel administration, and the risk of cardiovascular events over 18 months follow-up. A sub analysis examined the impact of rabeprazole, a proton pump inhibitor (PPI) less affected by CYP2C19.The CYP2C19 genotype was extensive metabolizer (EM) in 36%, intermediate metabolizer (IM) in 45%, and poor metabolizer (PM) in 19%. Platelet reactivity was significantly lower in the EM group than in the IM and PM groups (EM, IM, PM: 3560 ± 1404, 4203 ± 1302, 5084 ± 1007 AU•min, P < 0.05). The cardiovascular event rate was higher in the IM and PM groups than in the EM group (12.7% and 12.5% vs 1.6%; Hazard ratio for IM 10.6, P = 0.029; for PM 11.3, P = 0.040). No differences were seen between patients taking (N = 50) and not taking (N = 124) rabeprazole in residual platelet aggregation (4407 ± 1360 vs 4048 ± 1394, AU•min, P = 0.2782), or in cardiovascular events (10.0% vs 8.1%, HR 0.97, P = 0.97).

Conclusions

CYP2C19 genotype is associated with an increased risk of cardiovascular events following stent implantation in Japanese patients.     

High on clopidogrel treatment platelet reactivity is frequent in acute and rare in elective stenting and can be functionally overcome by switch of therapy

The benefit of adjusted antiplatelet therapy in patients with myocardial infarction after primary percutaneous coronary intervention is not well elucidated. We aimed to identify patients with high on treatment platelet reactivity and to gradually adjust antiplatelet therapy.