Enhanced Clopidogrel Responsiveness in Smokers

Investigation of smoking on the antiplatelet response to clopidogrel: Unravelling the smoker's paradox

The intricate relationship between smoking and the effects of the antiplatelet drug clopidogrel has been termed the "smoker's paradox". This paradox details the enhanced efficacy of clopidogrel in smokers compared to non-smokers. This review begins with an exploration of the proposed mechanisms of the smoker's paradox, particularly drawing attention to the induction of cytochrome P450 (CYP) isoenzymes via tobacco smoke, specifically the enzymes CYP1A2 and CYP2C19. Moreover, an investigation of the effects of genetic variability on the smoker's paradox was undertaken from both clinical and molecular perspectives, delving into the effects of ethnicity and genetic polymorphisms. The intriguing role of CYP1A2 genotypes and the response to clopidogrel in smoking and non-smoking populations was examined conferring insight into the individuality rather than universality of the smoker's paradox. CYP1A2 induction is hypothesised to elucidate the potency of smoking in exerting a counteracting effect in those taking clopidogrel who possess CYP2C19 loss of function polymorphisms. Furthermore, we assess the comparative efficacies of clopidogrel and other antiplatelet agents, namely prasugrel and ticagrelor. Studies indicated that prasugrel and ticagrelor provided a more consistent effect and further reduced platelet reactivity compared to clopidogrel within both smoking and non-smoking populations. Personalised dosing was another focus of the review considering patient comorbidities, genetic makeup, and smoking status with the objective of improving the antiplatelet response of those taking clopidogrel. In summation, this review provides insight into multiple areas of research concerning clopidogrel and the smoker's paradox taking into account proposed mechanisms, genetics, other antiplatelet agents, and personalised dosing.

Impact of smoking on one year functional outcomes after thrombectomy for young stroke patients

BACKGROUND

The incidence of stroke in young patients (20-50 years old) has increased in recent decades. Unlike the use of good functional outcomes to evaluate prognosis, excellent functional outcomes are a better indicator of return to work among younger patients. The rate of return to work increases with time after stroke. This study investigated the short term (3 months) and long term (1 year) predictors of excellent functional outcomes in young patients after endovascular thrombectomy (EVT).

METHODS

We included young patients who underwent EVT for acute ischemic stroke (AIS) due to large vessel occlusion within 6 hours after stroke onset between 2015 and 2021. Patients with intracerebral hemorrhage on pretreatment CT were excluded. The associations between clinical, imaging, and procedure variables, and excellent functional outcomes were analyzed using univariate and multivariable logistic regression analyses. An excellent functional outcome was defined as a modified Rankin Scale score of ≤1.

RESULTS

Of the 361 patients with AIS eligible for EVT, 55 young patients (aged 24-50 years) were included. Of these, 36.4% and 41.8% achieved excellent functional outcomes at 3 and 12 months, respectively. Multivariate analysis revealed that smoking was the independent negative predictor of both 3 month (adjusted OR (aOR) 0.232, 95% CI 0.058 to 0.928; p=0.039) and 12 month (aOR 0.180, 95% CI 0.044 to 0.741; p=0.018) excellent functional outcomes.

CONCLUSIONS

Current or former smoking habit was an independent negative predictor of both short term and long term excellent functional outcomes in young adults with AIS.

Live to die another day: novel insights may explain the pathophysiology behind smoker's paradox in SARS-CoV-2 infection

The severe acute respiratory coronavirus 2 (SARS-CoV-2) infection demonstrates a highly variable and unpredictable course. Several reports have claimed a smoker's paradox in coronavirus disease 2019 (COVID-19), in line with previous suggestions that smoking is associated with better survival after acute myocardial infarction and appears protective in preeclampsia. Several plausible physiological explanations exist accounting for the paradoxical observation of smoking engendering protection against SARS-CoV-2 infection. In this review, we delineate novel mechanisms whereby smoking habits and smokers' genetic polymorphism status affecting various nitric oxide (NO) pathways (endothelial NO synthase, cytochrome P450 (CYP450), erythropoietin receptor (EPOR); β-common receptor (βcR)), along with tobacco smoke modulation of microRNA-155 and aryl-hydrocarbon receptor (AHR) effects, may be important determinators of SARS-CoV-2 infection and COVID-19 course. While transient NO bioavailability increase and beneficial immunoregulatory modulations through the above-mentioned pathways using exogenous, endogenous, genetic and/or therapeutic modalities may have direct and specific, viricidal SARS-CoV-2 effects, employing tobacco smoke inhalation to achieve protection equals self-harm. Tobacco smoking remains the leading cause of death, illness, and impoverishment.

Unfolding the reality of the smoking paradox in a South Asian cohort of patients presenting with ST-elevation acute coronary syndrome undergoing primary percutaneous coronary intervention

Objectives

Smoking is a potent risk factor for coronary artery disease, but there is controversy about its protective nature in terms of prognosis in ST-elevation acute coronary syndrome patients undergoing primary percutaneous coronary intervention. So, the main objective of this study is to unfold this controversy in a South Asian population in terms of clinical angiographic parameters and its in-hospital outcomes.

Methods

In this study, we included 1756 consecutive patients diagnosed with ST-elevation acute coronary syndrome undergoing primary percutaneous coronary intervention. Patients were classified into smokers and non-smokers, and the in-hospital mortality rate was compared. Multivariable logistic regression analysis was performed to evaluate the paradoxical role of smoking.

Results

Smokers were younger (53.78 ± 11.16 years vs 56.43 ± 11.17 years; p < 0.001) and more frequently men (98.7% vs 69.9%; p < 0.001) and had less diabetes (19.6% vs 44.8%; p < 0.001) and hypertension (38.5% vs 64.9%; p < 0.001). Smokers presented less frequently in Killip III (5.6% vs 8.1%; p < 0.001) and Killip IV (2.5% vs 4.8%; p < 0.001). Smokers mostly had single vessel disease (41.7% vs 34.4%; p = 0.013), whereas non-smokers had the multi-vessel disease and frequently presented with total occlusion of the culprit vessel (64.6% vs 58.8%; p = 0.040). Smokers have significantly lesser mortality (1.8% vs 4.3%; p = 0.009) compared to non-smokers with an odds ratio of 0.41 (95% confidence interval (CI): 0.21-0.82, p = 0.011); however, adjusted odds ratio on multivariable analysis was 0.67 (95% CI: 0.31-1.41, p = 0.290).

Conclusions

The paradoxical protective role of smoking is the confounding effect of mainly younger age, less coronary artery disease burden, lower prevalence of diabetes and hypertension, and lower Killip III/IV at presentation.

Smoking, immunity, and cardiovascular prognosis: a study of plasma IgE concentration in patients with acute myocardial infarction

Background

Immunoglobulin E (IgE) is implicated in the pathogenesis of acute myocardial infarction (AMI), and smokers often exhibit elevated plasma IgE levels. However, it remains uncertain whether the role of smoking in the development and prognosis of AMI is influenced by IgE levels. This study aimed to investigate the potential contribution of IgE in mediating the association between smoking and AMI.

Methods

We conducted a prospective study involving 348 consecutive patients with chest discomfort who underwent coronary angiography. Plasma cotinine, an alkaloid present in tobacco, and IgE levels were measured. The patients were followed up for mean 39-months to assess their long-term prognosis based on major adverse cardiac and cerebrovascular events (MACCE).

Results

Our findings indicate that patients with AMI had higher plasma levels of cotinine and IgE. Univariate analyses demonstrated a positive association between plasma cotinine (OR = 1.7, 95% CI: 1.27-2.26, P < 0.001) and IgE (OR = 2.8, 95% CI: 1.75-4.39, P < 0.001) with AMI. Receiver operating characteristics analyses showed that the combined use of cotinine and IgE (AUC: 0.677) had a larger predictive performance compared to cotinine alone (AUC: 0.639) or IgE alone (AUC: 0.657), although the improvement did not reach statistical significance. Multivariable logistic regression revealed a positive association between plasma cotinine and AMI (OR = 1.70, 95% CI: 1.04-2.78, P = 0.036). Furthermore, the inclusion of plasma IgE in the regression model led to a decrease in the OR and 95% CI of plasma cotinine (OR = 1.66, 95% CI: 1.01-2.73, P = 0.048). Process mediation analyses showed a significant indirect effect of plasma cotinine on AMI mediated through increased plasma IgE. Kaplan-Meier analysis during a mean 39-months follow-up revealed that higher plasma levels of IgE were associated with an increased risk of MACCE following AMI (P = 0.047). However, in the context of the COX regression analysis, no significant correlation was observed between IgE, cotinine and AMI.

Conclusion

Cotinine exhibits a positive association with AMI, wherein IgE plays a mediating role. Elevated plasma levels of IgE was positively associated with AMI and poor prognosis, which further confirms the adverse role of smoking on the incidence of AMI and prognosis. (Clinical trial registration: ChiCTR2100053000).

Altered platelet reactivity, coagulation, endothelial and inflammatory markers early after smoking cessation verified with cotinine plasma concentration

BACKGROUND/INTRODUCTION

Cigarette smoking is a potent modifiable risk factor for coronary artery disease (CAD). However, little is known about alterations to prothrombotic state and platelet reactivity early after smoking cessation following percutaneous coronary interventions (PCI).

PURPOSE

We investigated alterations to platelet reactivity, coagulation and markers of platelet, endothelial, inflammatory and coagulation activation in clopidogrel-treated patients with CAD after PCI before and after smoking cessation.

METHODS

Smoking patients aged 18 years or older at least 30 days after PCI were recruited and encouraged to quit the habit. At baseline and at 30 days, we measured platelet reactivity with VerifyNow system, thrombomodulin, P-selectin, platelet factor 4 (CXCL4/PF4), citrullinated histone H3 (H3cit) and cotinine level.

RESULTS

Among 117 patients, 84 patients (72%) at a median age of 60.5 years (40 [interquartile range 30-47] pack-years) completed a 30-day follow-up. At day 30, 30 (35.7%) patients stopped smoking with cotinine level < 50 ng/ml. Baseline characteristics were similar in both groups. In smoking quitters a change in platelet reactivity was larger (Δ platelet reactivity units (PRU) 19 [2, 43] vs. -6 [-32, 37], p = 0.018), along with a change in P-selectin concentration (-11.82 [-23.62, 1.34] vs. 7.19 [-14.24, 17.19] ng/ml, p = 0.005). Positive correlations was noticed between cotinine and both P-selectin ( r = 0.23, p = 0.045) and CXCL4 (r = 0.27, p = 0.02).

CONCLUSION

After smoking cessation in CAD patients following PCI an increase in platelet reactivity and a decrease in P-selectin levels were observed. The risk of thrombotic complications post PCI might be paradoxically enhanced among patients who stopped smoking.

Pharmacokinetics and Pharmacodynamics of Approved and Investigational P2Y12 Receptor Antagonists

Coronary artery disease remains the major cause of mortality worldwide. Antiplatelet drugs such as acetylsalicylic acid and P2Y12 receptor antagonists are cornerstone treatments for the prevention of thrombotic events in patients with coronary artery disease. Clopidogrel has long been the gold standard but has major pharmacological limitations such as a slow onset and long duration of effect, as well as weak platelet inhibition with high inter-individual pharmacokinetic and pharmacodynamic variability. There has been a strong need to develop potent P2Y12 receptor antagonists with more favorable pharmacological properties. Prasugrel and ticagrelor are more potent and have a faster onset of action; however, they have shown an increased bleeding risk compared with clopidogrel. Cangrelor is highly potent and has a very rapid onset and offset of effect; however, its indication is limited to P2Y12 antagonist-naïve patients undergoing percutaneous coronary intervention. Two novel P2Y12 receptor antagonists are currently in clinical development, namely vicagrel and selatogrel. Vicagrel is an analog of clopidogrel with enhanced and more efficient formation of its active metabolite. Selatogrel is characterized by a rapid onset of action following subcutaneous administration and developed for early treatment of a suspected acute myocardial infarction. This review article describes the clinical pharmacology profile of marketed P2Y12 receptor antagonists and those under development focusing on pharmacokinetic, pharmacodynamic, and drug-drug interaction liability.

Safety and Efficacy of Stent-Assisted Coiling of Unruptured Intracranial Aneurysms Using Low-Profile Stents in Small Parent Arteries

BACKGROUND AND PURPOSE

Stent-assisted coiling of intracranial aneurysms arising from small vessels (≤ 2.0 mm) is a common procedure. However, data regarding its treatment outcomes are scarce. This study evaluated the clinical and radiologic outcomes of stent-assisted coiling using low-profile stents for aneurysms of small parent arteries.

MATERIALS AND METHODS

From November 2015 to October 2020, sixty-four patients with 66 aneurysms arising from parent arteries of ≤2.0 mm were treated with stent-assisted coiling using a Low-Profile Visualized Intraluminal Support Junior (LVIS Jr) or the Neuroform Atlas stent in a single institution. The clinical and radiologic data were retrospectively reviewed, and the risk factors for procedure-related complications were evaluated.

RESULTS

The LVIS Jr and Neuroform Atlas stents were used in 22 (33.3%) and 44 (66.7%) cases, respectively. Technical success was achieved in 66 cases (100%). Immediate postprocedural aneurysm occlusion grades assessed by the Raymond-Roy occlusion classification were I (57.6%), II (19.7%), and III (22.7%), respectively. Procedure-related complications occurred in 10 cases (15.2%), with 8 thromboembolic complications (12.1%) and 2 hemorrhagic complications (3.0%). Procedure-related morbidity was 4.5% without mortality. On multivariate analysis, current smoking (odds ratio = 7.1, P = .021) had a statistically significant effect on procedure-related complications.

CONCLUSIONS

Stent-assisted coiling of intracranial aneurysms with low-profile stents in small vessels (≤ 2.0 mm) had a 100% success rate and a 15.2% overall complication rate with 4.5% morbidity. Current smoking was a significant risk factor associated with procedure-related complications.

Comparison of effectiveness and safety between ticagrelor and clopidogrel in patients with acute coronary syndrome and on dialysis in Taiwan

AIMS

This study aimed to evaluate and compare the effectiveness and safety between clopidogrel and ticagrelor in acute coronary syndrome (ACS) with renal dysfunction.

METHODS

We conducted a retrospective cohort study on patients on chronic dialysis and whose admission diagnosis between 1 July 2013 and 31 December 2016 included ACS. The primary effectiveness endpoint was a major adverse cardiovascular event (MACE), and the primary safety endpoint was a major bleeding event. The application of propensity scores through the inverse probability of treatment weighting (IPTW) was applied to the study groups. Cox regression was used to estimate hazard ratios (aHRs) of study endpoints. In addition, the competing risk was adjusted using the Fine and Gray competing risk model.

RESULTS

There were 1915 patients in the clopidogrel group and 270 patients in the ticagrelor group. At 12 months, the ticagrelor group had higher risks for MACE (aHR with IPTW: 1.29; 95% CI 1.16-1.44); death (aHR with IPTW: 1.65; 95% CI 1.47-1.86) and cardiac death (subdistribution HR [SHR] with IPTW: 1.64; 95% CI 1.41-1.91), compared with those in the clopidogrel group. For major bleeding event, the risk was significantly higher with ticagrelor than with clopidogrel (SHR with IPTW: 1.49; 95% CI 1.34-1.65). In terms of the risk for any bleeding event, there was no significant difference between the two groups (SHR with IPTW: 1.05; 95% CI 0.95-1.17).

CONCLUSIONS

Compared with clopidogrel, ticagrelor was associated with higher MACE, death, cardiac death and major bleeding risk within 12 months in patients with ACS and on dialysis.

Polymorphisms of genes related to phase-I metabolic enzymes affecting the clinical efficacy and safety of clopidogrel treatment

Introduction: Clopidogrel is an antiplatelet medication described as a prodrug, which cannot exert the antiplatelet effect until being biotransformed to the active metabolite. It is commonly used to reduce the risk of blood coagulation in patients diagnosed with acute coronary syndrome, or ischemic stroke.Area covered: We reviewed published articles in PubMed and Google Scholar that focused on the mutations of CYP2C19, CYP3A4, CYP2C9, CYP2B6, and CYP1A2 genes related to clopidogrel clinical efficacy and safety.Expert opinion: Based on current pharmacogenetic studies, patients carrying CYP2C19*2, CYP2C19*3, CYP2C9*3, and CYP2B6*5 alleles may not respond to clopidogrel due to poor platelet inhibition efficacy revealed among them. In contrast, carriers of CYP2C19*17, CYP3A4*1G, and CYP1A2*1C alleles showed a more significant antiplatelet effect in clopidogrel users and expected to have a protective role as a genetic factor against cardiovascular events. Genotyping for either CYP2C19, CYP3A4, CYP2C9, CYP2B6, or CYP1A2 variants is not recommended when considering clopidogrel treatment for patients, as some trials showed specific non-genetic factors (e.g. age and diabetes) that could affect clopidogrel responsiveness. Instead, platelets inhibition tests could be used as predictors of the clinical efficacy of clopidogrel treatment. Other P2Y12 receptor inhibitors should be considered as alternative medications.

Impact of genetic variants of selected cytochrome P450 isoenzymes on pharmacokinetics and pharmacodynamics of clopidogrel in patients co-treated with atorvastatin or rosuvastatin

PURPOSE

Impaired antiplatelet effect of clopidogrel (CLP) can result from drug-drug interactions and genetic polymorphisms of drug-metabolizing enzymes. The aim of the study was to evaluate the effect of genetic polymorphisms of ABCB1 and the selected cytochrome P450 isoenzymes on the pharmacodynamics and pharmacokinetics of CLP and its metabolites in patients co-treated with atorvastatin or rosuvastatin.

METHODS

The study involved 50 patients after coronary angiography/angioplasty treated with CLP and atorvastatin (n = 25) or rosuvastatin (n = 25) for at least 6 months. Plasma concentrations of CLP, diastereoisomers of thiol metabolite (inactive H3 and active H4), and inactive CLP carboxylic acid metabolite were measured by UPLC-MS/MS method. Identification of the CYP2C19*2, CYP2C19*17, CYP3A4*1G, CYP1A2*1F, and ABCB1 C3435T genetic polymorphisms was performed by PCR-RFLP, while platelet reactivity units (PRU) were tested using the VerifyNow P2Y12 assay.

RESULTS

There were significant differences in the pharmacokinetic parameters of the H4 active metabolite of CLP in the atorvastatin and rosuvastatin group divided according to their CYP2C19 genotype. There were no significant associations between CYP3A4, CYP1A2, and ABCB1 genotypes and pharmacokinetic parameters in either statin groups. In the multivariate analysis, CYP2C19*2 genotype and non-genetic factors including BMI, age, and diabetes significantly affected platelet reactivity in the studied groups of patients (P < 0.01). In the atorvastatin group, CYP2C19*2, CYP3A4*1G, and ABCB1 C3435T TT genotypes were independent determinants of PRU values (P < 0.01).

CONCLUSION

The CYP2C19*2 allele is the primary determinant of the exposition to the H4 active metabolite of clopidogrel and platelet reactivity in patients co-treated with atorvastatin or rosuvastatin.

Impact of Smoking on Platelet Reactivity and Clinical Outcomes After Percutaneous Coronary Intervention

Background:

Smoking is a potent risk factor for coronary artery disease; however, prior studies describe increased platelet inhibition with clopidogrel among smokers, and some studies report improved outcomes among smokers, a finding described as the smoker’s paradox. This study assessed the relationship between platelet reactivity and clinical outcomes after percutaneous coronary interventions among current smokers and nonsmokers.

Methods:

ADAPT-DES (Assessment of Dual Antiplatelet Therapy With Drug-Eluting Stents) was a prospective, multicenter registry of patients treated with coronary drug-eluting stents. Platelet reactivity was assessed by the VerifyNow point-of-care assay; high on-treatment platelet reactivity (HPR) was defined as P2Y12 reaction units >208. A propensity-adjusted multivariable analysis was performed to determine the relationship between current smoking, platelet reactivity, and subsequent adverse events.

Results:

Among 8582 patients, 22.6% were active smokers at the time of their percutaneous coronary intervention procedure. Current smokers were younger and had fewer comorbidities compared with nonsmokers. Current smokers had lower mean P2Y12 reaction units and lower rates of HPR compared with nonsmokers. Current smokers had similar rates of adverse events compared with nonsmokers. HPR was associated with higher rates of adverse events for both smokers and nonsmokers; however, there was evidence of interaction between smoking status and the effect of HPR. Smokers with HPR had significantly higher rates of stent thrombosis. Adverse event rates were highest among current smokers with HPR.

Conclusions:

Current smoking was associated with lower P2Y12 reaction units and lower rates of HPR on average; however, the combination of current smoking and HPR was associated with high rates of stent thrombosis.

Clinical Trial Registration:

URL: https://www.clinicaltrials.gov . Unique identifier: NCT00638794.

Cardiovascular Pharmacogenomics: Does It Matter If You're Black or White?

Race and ancestry have long been associated with differential risk and outcomes to disease as well as responses to medications. These differences in drug response are multifactorial with some portion associated with genomic variation. The field of pharmacogenomics aims to predict drug response in patients prior to medication administration and to uncover the biological underpinnings of drug response. The field of human genetics has long recognized that genetic variation differs in frequency between ancestral populations, with some single nucleotide polymorphisms found solely in one population. Thus far, most pharmacogenomic studies have focused on individuals of European and East Asian ancestry, resulting in a substantial disparity in the clinical utility of genetic prediction for drug response in US minority populations. In this review, we discuss the genetic factors that underlie variability to drug response and known pharmacogenomic associations and how these differ between populations, with an emphasis on the current knowledge in cardiovascular pharmacogenomics.

Prevalence of poor biological response to clopidogrel

The existence of poor biological response to clopidogrel has been shown in some patients. Despite the increasing number of studies, this phenomenon remains difficult to quantify. We performed a systematic review to estimate the prevalence of poor biological response to clopidogrel and investigate the factors known to modulate this. An exhaustive search was performed. Altogether 171 publications were identified, providing data for a total of 45,664 subjects. The estimated prevalence of poor biological response to clopidogrel ranged from 15.9% to 49.5% according to the platelet function assay employed. The assays most frequently used were light transmittance aggregometry (LTA), the vasodilator-stimulated phosphoprotein (VASP) assay and the Verify -now® assay. For all these assays, higher cut-off values were associated with a lower prevalence of poor biological response to clopidogrel. However, when choosing a fixed cut-off point for each assay, the prevalence of poor biological response to clopidogrel was highly variable suggesting that other factors could modulate poor biological response to clopidogrel. Finally, none of the studied factors could apparently explain the variability of poor biological response to clopidogrel. This meta-analysis shows that the prevalence of poor biological response depends on the assay employed, the cut-off value and on various unidentified additional factors.

Clopidogrel non-responsiveness in patients undergoing percutaneous coronary intervention using the VerifyNow test: frequency and predictors

Objectives

Stent thrombosis and death after percutaneous coronary intervention (PCI) can be caused by a phenomenon known as clopidogrel non-responsiveness which has been shown to occur in approximately 5%–44% of patients. We investigated the responsiveness of clopidogrel in an Iraqi series of cases. Our aim was to determine for the first time the frequency and predictors of clopidogrel non-responsiveness among Iraqi patients with ischaemic heart disease undergoing PCI.

Methods

The study was conducted at the Cardiac Catheterization Center, Baghdad Teaching Hospital, Medical City, from January to May 2014, and included patients who presented for PCI. A platelet aggregation test was performed for those patients using the VerifyNow system.

Results

A total of 115 patients (mean age: 58.3±10.1 years; male sex: 73.9%) were included in the study. 18.3% of the study population were clopidogrel non-responders, which was comparable with the results of a Chinese study (20.28%, P=0.796) but contrasted with other reports from Jordan, Brazil and Thailand. The major independent predictive factor for non-responsiveness in our report was diabetes mellitus (OR 5.96, 95% CI 2.23 to 13.71; P=0.001), followed by hypertension (OR 4.135, P=0.035), obesity (OR 3.44, P=0.037) and male sex (OR 3.039, P=0.045). Previous use of clopidogrel (OR 0.17, P=0.02) and younger age (OR 0.72, P=0.026) were identified as protective factors.

Conclusions

In this study, 18.3% of patients were non-responders to clopidogrel and the major independent predictive factors for non-responsiveness were diabetes mellitus, hypertension, obesity and male sex.

Cigarette Smoking Does Not Enhance Clopidogrel Responsiveness After Adjusting VerifyNow P2Y12 Reaction Unit for the Influence of Hemoglobin Level

OBJECTIVES

The authors performed this analysis to examine whether the enhanced clopidogrel responsiveness in current smokers is maintained after adjusting the influence of hemoglobin on VerifyNow P2Y12 reaction unit (PRU).

BACKGROUND

PRU is consistently reported to be lower in current smokers. However, PRU has a significant inverse relationship with hemoglobin level, and smokers have higher hemoglobin levels. Because the association between PRU and hemoglobin is likely to be an in vitro phenomenon, we hypothesized that the observed difference in PRU between nonsmokers and current smokers is the result of confounding effect of hemoglobin rather than true difference in platelet reactivity.

METHODS

Three cohorts were combined for the analysis (SNUBH [Seoul National University Bundang Hospital], n = 459; CILON-T [influence of CILostazol-based triple antiplatelet therapy ON ischemic complication after drug-eluting stenT implantation], n = 715; HOST-ASSURE [Harmonizing Optimal Strategy for Treatment of coronary artery stenosis - sAfety & effectiveneSS of drug-elUting stents & antiplatelet REgimen], n = 1,357). The final combined cohort consisted of 1,314 patients who underwent percutaneous coronary intervention and had VerifyNow P2Y12 assay results. General linear model (analysis of covariance) was used to control the effect of hemoglobin on PRU.

RESULTS

A significant inverse correlation was observed between PRU and hemoglobin (r = -0.389; p < 0.001). Current smokers showed a significantly higher hemoglobin level (13.5 ± 1.6 vs. 14.4 ± 1.5; p < 0.001) but lower PRU level (230.1 ± 90.7 vs. 212.2 ± 83.6; p < 0.001). After adjusting the influence of hemoglobin on PRU, there was no difference in PRU between nonsmokers and current smokers (224.1 [95% confidence interval: 218.7 to 229.5] vs. 225.3 [95% confidence interval: 217.2 to 233.3]; p = 0.813).

CONCLUSIONS

The observed difference in PRU between nonsmokers and current smokers is largely attributable to the difference in hemoglobin level. Enhanced clopidogrel responsiveness in cigarette smokers is not confirmed in this study and the concept of the smokers' paradox needs further validation.

Clinical characteristics and prognosis of acute myocardial infarction in young smokers and non-smokers (≤ 45 years): a systematic review and meta-analysis

The effect of smoking on the prognosis of young patients with acute myocardial infarction (AMI) is inconclusive. We enrolled 2188 young AMI patients (≤ 45 years) from the cardiac center of the Chinese PLA General Hospital and Anzhen Hospital and analyzed their clinical characteristics and prognosis. We also searched the PubMed, EMBASE, and Cochrane Central Register of Controlled Trials electronic databases for January 2001 to March 2017 and considered for inclusion in a meta-analysis those clinical trials that compared prognoses of young smokers and non-smokers with AMI. The proportion of males and alcohol users was higher in young AMI smokers than in non-smokers; the proportion of hypertension was slightly lower. There was no difference in medical treatment between smokers and non-smokers. No differences were evident between smokers and non-smokers regarding in-hospital cardiac events and major adverse cardiovascular events on follow-up, including incidence of stroke. For young AMI patients, smoking did not lead to poorer prognosisin comparison with not smoking. This “smoker's paradox” needs to be confirmed by more randomized controlled multicenter prospective clinical trials.

A laboratory association between hemoglobin and VerifyNow P2Y12 reaction unit: A systematic review and meta-analysis

BACKGROUND

VerifyNow P2Y12 assay is used widely to evaluate residual platelet reactivity in patients taking P2Y12 receptor antagonists. However, a laboratory association between VerifyNow P2Y12 reaction unit (PRU) and hemoglobin, which might lead to wrong interpretation of the data, is reported. We performed these systematic review and meta-analysis to clearly define the relationship between PRU and hemoglobin and to elucidate whether the relationship, if any, is a true biological association or is just a laboratory error.

METHODS

Through a comprehensive electronic and manual search, 10 studies were selected for the cohort level meta-analysis. Among 10 studies, we were able to retrieve the raw data of 5 studies, and a patient-level meta-analysis was performed. Potential publication bias was searched by funnel plot analysis and was actively adjusted, if present, by trim and fill method.

RESULTS

The pooled analysis revealed a significant inverse correlation between PRU and hemoglobin (r=-0.349; P<.001; 10 studies with 4,793 patients). VerifyNow P2Y12 base unit, which reflects off-drug platelet reactivity, was also inversely correlated with hemoglobin (r=-0.526; P<.001; 8 studies with 4,395 patients). % Inhibition (r=0.081; P=.059; 6 studies with 3,832 patients) and ΔPRU (r=-0.037; P=.188; 5 studies with 3,521 patients) were not associated with hemoglobin. A significant inverse association between PRU and hemoglobin was also observed in the patient-level meta-analysis (3,533 patients pooled from 5 studies; r=-0.335; P<.001). Light transmission aggregometry (r=0.160; P=.072; 4 studies with 1,144 patients) and multiple electrode platelet aggregometry (r=-0.029; P=.394; 3 studies with 7,645 patients) showed no significant association with hemoglobin.

CONCLUSIONS

A significant inverse association was observed between PRU and hemoglobin which is likely to be a laboratory error. Clinicians should be aware that this association might lead to wrong interpretation of the data.

Pharmacokinetic and Pharmacodynamic Responses to Clopidogrel: Evidences and Perspectives

Clopidogrel has significantly reduced the incidence of recurrent atherothrombotic events in patients with acute coronary syndrome (ACS) and in those undergoing percutaneous coronary intervention (PCI). However, recurrence events still remain, which may be partly due to inadequate platelet inhibition by standard clopidogrel therapy. Genetic polymorphisms involved in clopidogrel’s absorption, metabolism, and the P2Y12 receptor may interfere with its antiplatelet activity. Recent evidence indicated that epigenetic modification may also affect clopidogrel response. In addition, non-genetic factors such as demographics, disease complications, and drug-drug interactions can impair the antiplatelet effect of clopidogrel. The identification of factors contributing to the variation in clopidogrel response is needed to improve platelet inhibition and to reduce risk for cardiovascular events. This review encompasses the most recent updates on factors influencing pharmacokinetic and pharmacodynamic responses to clopidogrel.

Potential Usefulness of Clopidogrel Pharmacogenetics in Cerebral Endovascular Procedures and Carotid Artery Stenting

BACKGROUND

Previous reports have shown inadequate response to dual antiplatelet therapy (DAPT) with aspirin and clopidogrel in 5-30% of patients undergoing percutaneous coronary interventions (PCI), due mostly to clopidogrel resistance. This prevalence increases up to 66% in patients undergoing neurointerventional procedures. However, clinical significance of CYP2C19 genotypes in neurointerventional procedures or carotid artery stenting (CAS) is unknown.

OBJECTIVE

The purpose of this review is to update our current knowledge and understanding of the pharmacogenetic basis for poor clopidogrel responsiveness in patients undergoing CAS and endovascular interventions as well as to explore usefulness of genotyping to reduce the rate of procedure-related thrombosis that results in ischemic complications.

METHOD

A literature search for pharmacogenetic studies in cerebral endovascular interventions and CAS was conducted on three databases using a list of the most relevant pharmacogenetic biomarkers.

RESULTS

The review included 7 papers involving 3 genetic polymorphisms on CYP2C19 and 442 subjects. Patients harboring at least one loss-of-function CYP2C19 polymorphism (e.g., CYP2C19*2 and *3) are at an increased risk of thromboembolic complications such as stent thrombosis following neurointerventional procedures. Notably, patients who carry the gain-of-function CYP2C19*17 allele may have increased risk of ischemic events following endovascular treatment, independent of clopidogrel responsiveness.

CONCLUSION

Studies assessing the influence of CYP2C19 polymorphisms on high on-treatment platelet reactivity in CAS and cerebrovascular disease patients are still limited and need further validation in large multicenter studies. This review covers an important topic in the field of antiplatelet therapy for cerebral endovascular procedures and CAS.

Does "smoker's paradox" exist in clopidogrel-treated Turkish patients with acute coronary syndrome

Previously conducted studies revealed that smoking enhanced the efficacy of clopidogrel by increasing formation of the active metabolite (AM) from the prodrug through induction of the cytochrome CYP1A2. The expression of cytochrome enzymes depends on genotype and no data exists in literature conducted in Turkish patients comparing the clopidogrel responsiveness between active smokers and non-active smokers treated with clopidogrel. In this study, our aim was to investigate the clopidogrel responsiveness in clopidogrel-treated Turkish acute coronary syndrome (ACS) patients according to their smoking status. We retrospectively enrolled 258 patients who were hospitalized due to ACS. Clinical variables of the patients, especially smoking status were recorded. Clopidogrel resistance was evaluated by using adenosine diphosphate (ADP) induced platelet aggregometry. Clopidogrel resistance was detected as a change in maximal aggregation ≤20% from baseline. A total of 139 patients were active smokers while 12 were former smokers. 107 patients did not have a history of smoking. Ten of the smokers were hyporesponsive to clopidogrel, whereas 36 of non-smokers were hyporesponsive to clopidogrel (p < 0.001). Receiver-operating characteristic curve analysis demonstrated that Au-min value >612.5 predicted the clopidogrel resistance with a sensitivity of 60% (OR: 100.65, %95 CI = 19.996-506.615 p < 0.001). Results of this study demonstrated that ADP responses were lower in smokers receiving clopidogrel and aspirin than in non-smokers receiving the same drug regimen. This finding indicates that smoking was related to an enhanced clopidogrel responsiveness in Turkish patients hospitalized due to ACS, suggesting that "smoker's paradox" probably exists in Turkish ACS patients.

The pharmacogenetic control of antiplatelet response: candidate genes and CYP2C19

INTRODUCTION

Aspirin, clopidogrel, prasugrel and ticagrelor are antiplatelet agents for the prevention of ischemic events in patients with acute coronary syndromes (ACS), percutaneous coronary intervention (PCI) and other indications. Variability in response is observed to different degrees with these agents, which can translate to increased risks for adverse cardiovascular events. As such, potential pharmacogenetic determinants of antiplatelet pharmacokinetics, pharmacodynamics and clinical outcomes have been actively studied.

AREAS COVERED

This article provides an overview of the available antiplatelet pharmacogenetics literature. Evidence supporting the significance of candidate genes and their potential influence on antiplatelet response and clinical outcomes are summarized and evaluated. Additional focus is directed at CYP2C19 and clopidogrel response, including the availability of clinical testing and genotype-directed antiplatelet therapy.

EXPERT OPINION

The reported aspirin response candidate genes have not been adequately replicated and few candidate genes have thus far been implicated in prasugrel or ticagrelor response. However, abundant data support the clinical validity of CYP2C19 and clopidogrel response variability among ACS/PCI patients. Although limited prospective trial data are available to support the utility of routine CYP2C19 testing, the increased risks for reduced clopidogrel efficacy among ACS/PCI patients that carry CYP2C19 loss-of-function alleles should be considered when genotype results are available.

Pharmacokinetic drug interactions with clopidogrel: updated review and risk management in combination therapy

Background

Coprescribing of clopidogrel and other drugs is common. Available reviews have addressed the drug–drug interactions (DDIs) when clopidogrel is as an object drug, or focused on combination use of clopidogrel and a special class of drugs. Clinicians may still be ignorant of those DDIs when clopidogrel is a precipitant drug, the factors determining the degree of DDIs, and corresponding risk management.

Methods

A literature search was performed using PubMed, MEDLINE, Web of Science, and the Cochrane Library to analyze the pharmacokinetic DDIs of clopidogrel and new P2Y₁₂ receptor inhibitors.

Results

Clopidogrel affects the pharmacokinetics of cerivastatin, repaglinide, ferulic acid, sibutramine, efavirenz, and omeprazole. Low efficacy of clopidogrel is anticipated in the presence of omeprazole, esomeprazole, morphine, grapefruit juice, scutellarin, fluoxetine, azole antifungals, calcium channel blockers, sulfonylureas, and ritonavir. Augmented antiplatelet effects are anticipated when clopidogrel is coprescribed with aspirin, curcumin, cyclosporin, St John’s wort, rifampicin, and angiotensin-converting enzyme inhibitors. The factors determining the degree of DDIs with clopidogrel include genetic status (eg, cytochrome P540 [CYP]2B6*6, CYP2C19 polymorphism, CYP3A5*3, CYP3A4*1G, and CYP1A2-163C.A), species differences, and dose strength. The DDI risk does not exhibit a class effect, eg, the effects of clopidogrel on cerivastatin versus other statins, the effects of proton pump inhibitors on clopidogrel (omeprazole, esomeprazole versus pantoprazole, rabeprazole), the effects of rifampicin on clopidogrel versus ticagrelor and prasugrel, and the effects of calcium channel blockers on clopidogrel (amlodipine versus P-glycoprotein-inhibiting calcium channel blockers). The mechanism of the DDIs with clopidogrel involves modulating CYP enzymes (eg, CYP2B6, CYP2C8, CYP2C19, and CYP3A4), paraoxonase-1, hepatic carboxylesterase 1, P-glycoprotein, and organic anion transporter family member 1B1.

Conclusion

Effective and safe clopidogrel combination therapy can be achieved by increasing the awareness of potential changes in efficacy and toxicity, rationally selecting alternatives, tailoring drug therapy based on genotype, checking the appropriateness of physician orders, and performing therapeutic monitoring.

Personalized antiplatelet and anticoagulation therapy: applications and significance of pharmacogenomics

In recent years, substantial effort has been made to better understand the influence of genetic factors on the efficacy and safety of numerous medications. These investigations suggest that the use of pharmacogenetic data to inform physician decision-making has great potential to enhance patient care by reducing on-treatment clinical events, adverse drug reactions, and health care-related costs. In fact, integration of such information into the clinical setting may be particularly applicable for antiplatelet and anticoagulation therapeutics, given the increasing body of evidence implicating genetic variation in variable drug response. In this review, we summarize currently available pharmacogenetic information for the most commonly used antiplatelet (ie, clopidogrel and aspirin) and anticoagulation (ie, warfarin) medications. Furthermore, we highlight the currently known role of genetic variability in response to next-generation antiplatelet (prasugrel and ticagrelor) and anticoagulant (dabigatran) agents. While compelling evidence suggests that genetic variants are important determinants of antiplatelet and anticoagulation therapy response, significant barriers to clinical implementation of pharmacogenetic testing exist and are described herein. In addition, we briefly discuss development of new diagnostic targets and therapeutic strategies as well as implications for enhanced patient care. In conclusion, pharmacogenetic testing can provide important information to assist clinicians with prescribing the most personalized and effective antiplatelet and anticoagulation therapy. However, several factors may limit its usefulness and should be considered.

Genetic polymorphisms in promoter and intronic regions of CYP1A2 gene in Roma and Hungarian population samples

The purpose of this study was to determine the interethnic differences of four CYP1A2 drug metabolizing enzyme variants. A total of 404 Roma and 396 Hungarian healthy subjects were genotyped for -163C>A, -729C>T, -2467delT and -3860G>A variants of CYP1A2 by RT-PCR and PCR-RFLP technique. The -3860A and -729T allele were not detectable in Roma samples, while in Hungarian samples were present with 2.02% and 0.25% prevalence, respectively. There was a 1.5-fold difference in presence of homozygous -163AA genotype between Hungarian and Roma samples (49.5% vs. 31.9%, p<0.001). The -163A allele frequency was 68.6% in Hungarians and 56.9% in Romas (p=0.025). The -2467delT allele frequency was 6.81% in Roma group and 5.81% in Hungarians. The most frequent allelic constellation was -3860G/-2467T/-729C/-163A in both populations. In conclusion, Hungarians have markedly elevated chance for rapid metabolism of CYP1A2 substrates, intensified procarcinogen activation and increased risk for cancers.

Impact of smoking status on platelet function and clinical outcomes with prasugrel vs. clopidogrel in patients with acute coronary syndromes managed without revascularization: Insights from the TRILOGY ACS trial

BACKGROUND

To further explore the impact of smoking on antiplatelet activity and treatment response, we evaluated time-dependent relationships between smoking status with on-treatment platelet reactivity and clinical outcomes for prasugrel vs. clopidogrel in patients with acute coronary syndromes managed medically without revascularization.

METHODS AND RESULTS

A total of 7062 patients aged <75 years from the primary TRILOGY ACS cohort randomized to prasugrel vs. clopidogrel were evaluated through 30 months by baseline and time-dependent smoking status with adjusted proportional-hazards models. A total of 1994 participants (28%) [corrected] were included in a platelet function sub-study evaluating serial P2Y12 reaction unit (PRU) measurements. Current smokers (n = 1566 [22%]) at baseline had fewer comorbidities compared with non-smokers; nearly half quit smoking during follow-up. Although median on-treatment PRU values were lower with prasugrel vs. clopidogrel, persistent smokers had lower serial PRU values in both treatment groups compared with non-smokers, with no differential interaction of treatment response by smoking status. The frequency of cardiovascular death, myocardial infarction, or stroke in current smokers was significantly lower with prasugrel (11.7%) vs. clopidogrel (18.6%), but there was no difference in non-smokers (13.8% vs. 13.7%), with significant interaction between treatment and baseline smoking status (P = .0002). Bleeding events occurred more frequently in prasugrel-treated patients with no significant interaction between treatment and baseline smoking status.

CONCLUSIONS

Among medically managed ACS patients <75 years of age, the risk of ischemic outcomes was significantly reduced with prasugrel vs. clopidogrel among smokers vs. non-smokers. No interaction between on-treatment platelet reactivity and smoking status was found.

Cilostazol eliminates adverse smoking outcome in patients with drug-eluting stent implantation

BACKGROUND

The present study investigated whether cilostazol can eliminate adverse smoking outcome after percutaneous coronary intervention (PCI).

METHODS AND RESULTS

A total of 914 patients with successful drug-eluting stent (DES) implantation were randomly assigned to dual antiplatelet therapy (DAT; aspirin and clopidogrel, n=457) or to triple antiplatelet therapy (TAT; DAT with cilostazol, n=457). The effect of smoking on 2-year major adverse cardio/cerebrovascular events (MACCE) in both the TAT and DAT groups was evaluated. Total MACCE were not significantly different between the 2 anti-platelet regimens (9.8% in TAT vs. 11.4% in DAT groups, P=0.45), but the adverse effects of smoking on clinical outcome were different between DAT vs. TAT. Current smokers had a higher prevalence of MACCE than non-smokers in the DAT group (16.7% vs. 9.5%, P=0.04). In the TAT group, however, the adverse effect of smoking was abolished (9.2% vs. 10.1%, P=0.85). Regarding the effects of smoking on the antiplatelet effects of DAT or TAT, post-treatment platelet reactivity (in P2Y12 reaction units; PRU) in current smokers was not significantly lower than that in non-smokers in the DAT group, whereas, in the TAT group, it was significantly lower than that of non-smokers (189±88 vs. 216±89 PRU, P=0.01).

CONCLUSIONS

Adverse clinical effects of smoking may be eliminated by the addition of cilostazol to DAT after DES implantation. This may be due to the stimulation of cilostazol's antiplatelet effects by smoking.

Impact of smoking on long-term outcomes in patients with atherosclerotic vascular disease treated with aspirin or clopidogrel: insights from the CAPRIE trial (Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events)

OBJECTIVES

The goal of this study was to investigate the differential efficacy of clopidogrel or aspirin monotherapy according to smoking status in patients with atherosclerotic vascular disease.

BACKGROUND

Smoking enhances clopidogrel-induced platelet inhibition, which may explain the higher relative benefit among smokers observed in trials evaluating dual antiplatelet therapy. Whether smoking has an impact on clinical outcomes in patients requiring a single antiplatelet agent remains unknown.

METHODS

This was a post-hoc analysis of the CAPRIE (Clopidogrel Versus Aspirin in Patients at Risk of Ischemic Events) trial that compared clopidogrel and aspirin monotherapy in patients (N = 19,184) with atherosclerotic vascular disease.

RESULTS

Current smokers (n = 5,688) had an increased risk of ischemic events compared with never smokers (n = 4,135; hazard ratio [HR]: 1.24 [95% confidence interval (CI): 1.08 to 1.42]) and ex-smokers (n = 9,381; HR: 1.32 [95% CI: 1.18 to 1.47]) (p < 0.001). Clopidogrel was associated with a reduction in ischemic events among current smokers (8.3% vs. 10.8%; HR: 0.76 [95% CI: 0.64 to 0.90]), whereas no benefit over aspirin was seen in the combined group of ex-smokers/never-smoked patients (10.4% vs. 10.6%; HR: 0.99 [95% CI: 0.89 to 1.10]; p = 0.01 for interaction). Among current smokers, clopidogrel also reduced myocardial infarction, vascular death, and death from any cause compared with aspirin. No interaction between smoking status and study treatment was observed for bleeding events.

CONCLUSIONS

In a post-hoc analysis of the CAPRIE population, current smokers appeared to have enhanced benefit with clopidogrel therapy for secondary prevention compared with aspirin. These results should be considered hypothesis generating for future prospective studies assessing the impact of specific platelet-inhibiting strategies according to smoking status.

Comparison of antiplatelet efficacy and tolerability of clopidogrel napadisilate with clopidogrel bisulfate in coronary artery disease patients after percutaneous coronary intervention: a prospective, multicenter, randomized, open-label, phase IV, noninferiority trial

BACKGROUND

Clopidogrel bisulfate, a potent antiplatelet agent, has a pivotal role in the prevention and treatment of atherothrombotic disease. Clopidogrel napadisilate, a different salt preparation of clopidogrel, has been developed and approved in Korea and several European countries. Recent studies have suggested that clopidogrel napadisilate might have improved stability and comparable bioequivalence to clopidogrel bisulfate. However, these 2 clopidogrel preparations have not been compared in terms of efficacy and tolerability in patients with coronary artery disease (CAD) who underwent percutaneous coronary intervention (PCI).

OBJECTIVE

We sought to investigate the antiplatelet efficacy and safety profile of clopidogrel napadisilate compared with clopidogrel bisulfate in CAD patients after PCI.

METHODS

This was a randomized, multicenter, open-label, Phase IV, noninferiority clinical trial. We prospectively recruited CAD patient in 6 institutions in Korea between October 2010 and November 2011. Patients who underwent PCI were randomly assigned to the test group (clopidogrel napadisilate plus aspirin) or control group (clopidogrel bisulfate plus aspirin). Antiplatelet efficacy and safety profile were assessed after 4 weeks of maintenance treatment. The primary end point was noninferiority of the percentage of P2Y(12) inhibition, measured by point-of-care assay. The rate of major adverse cardiovascular events (MACE), as a secondary end point, was compared between the 2 clopidogrel preparations. To assess tolerability, we evaluated the incidence, severity, and causal relation of adverse events (AEs) of 2 groups.

RESULTS

A total of 169 patients were screened, and 127 patients completed the study (64 in the test group and 63 in the control group; P = 0.296). The baseline characteristics of patients did not differ significantly between the treatment groups. The between-group difference in percentage of P2Y(12) inhibition did not exceed the prespecified limit for noninferiority (P for noninferiority = 0.032; 95% CI, -8.33 to 5.53). With respect to the risk of MACE, no significant difference was found in the incidence of myocardial infarction or stroke between the groups (1 in the test group and 2 in the control group; P > 0.99); no mortality was reported in either group. The tolerability of clopidogrel napadisilate was comparable with that of clopidogrel bisulfate in terms of all AEs, drug-related AEs, and serious AEs (all AEs: test group, 33.3%; control group, 32.9% [P > 0.99]; drug-related AEs: test group, 4.17%; control group, 0% [P = 0.113]; serious AEs: test group, 1.39%; control group, 5.26% [P=0.367]).

CONCLUSIONS

In this study of CAD Korean patients who have undergone PCI, the antiplatelet efficacy of clopidogrel napadisilate was noninferior to that of clopidogrel bisulfate after 4 weeks of maintenance treatment. No statistically significant difference was found in tolerability between the 2 treatment groups.

The impact of smoking on clinical efficacy and pharmacodynamic effects of clopidogrel: a systematic review and meta-analysis

CONTEXT

Previous findings regarding the relationship between smoking and clopidogrel effects were considerably discrepant.

OBJECTIVE

To assess the impact of smoking on clinical and pharmacodynamic response to clopidogrel.

DATA SOURCES

Medline, EMBASE and the Cochrane Library through January 2013 were searched. Reference lists of pertinent literatures and abstracts of major cardiovascular conferences were screened.

STUDY SELECTION

Clinical and laboratory studies, which reported major adverse cardiovascular events and on-clopidogrel platelet reactivity categorised by smoking status respectively, were selected.

DATA EXTRACTION

Descriptive and quantitative data were extracted. The main analyses were performed under a random-effects model. For clinical studies, HR estimates were synthesised according to smoking status; for laboratory studies, standardised mean difference (SMD) of on-clopidogrel platelet reactivity and OR for high on-clopidogrel platelet reactivity were pooled. Heterogeneity was quantified by computing I(2) statistic.

RESULTS

Of the 1869 citations retrieved, seven clinical studies and 12 laboratory studies involving 111 132 patients with established cardiovascular disease and 6658 patients with acute coronary syndrome and/or stent deployment, respectively, were included for meta-analysis. Pooled clinical results showed that an intensified antiplatelet regimen involving clopidogrel was associated with 10% reduced risk for major adverse cardiovascular events among non-current smokers (HR 0.90; 95% CI 0.85 to 0.96), while this clinical benefit was enhanced by 2.9-fold among current smokers (HR 0.71; 95% CI 0.62 to 0.80). Pooled analysis of laboratory studies revealed that current smokers had significantly lower on-clopidogrel platelet reactivity (SMD -0.30; 95% CI -0.46 to -0.15) but, notably, there was considerable inter-study heterogeneity (I(2) 76.2%; p=0.000). The analysis based on four studies (n=1423) suggested a significantly lower odds of high on-clopidogrel platelet reactivity among current smokers than those among never smokers (OR 0.33; 95% CI 0.22 to 0.43).

CONCLUSIONS

Smoking appears to positively modify the relative clinical efficacy and pharmacodynamic effects of clopidogrel.

Thienopyridine efficacy and cigarette smoking status

Dual antiplatelet therapy with aspirin and a P2Y12 receptor blocker is an established regimen to reduce the risk of ischemic event occurrence in patients with high-risk cardiovascular (CV) disease. Cigarette smoking is an important cardiovascular risk factor. However, several investigators have reported what may be termed a "new" "smoker's paradox", whereby clopidogrel-treated nonsmokers appear to have either less or no CV-event reduction when compared to the substantial CV-event reduction in clopidogrel-treated smokers based on several large-scale trials. This "smoker's paradox" observed in multiple clinical outcome studies is also supported by emerging "real-world" data that also suggest clopidogrel nonsmokers do not fare as well as smokers treated with clopidogrel. In support of the new "smoker's paradox", pharmacodynamic studies have also shown that smoking status influences clopidogrel responsiveness in healthy volunteers, acute coronary syndrome patients, and patients treated with percutaneous coronary intervention. Finally, there is a substantial, albeit not entirely consistent, body of pharmacodynamic and clinical outcome data supporting a reduced antiplatelet effect of clopidogrel in non-smokers as compared to smokers. The clinical relevance of this interaction has never been demonstrated in a prospective trial. The focus of this review is to critically evaluate the reported interaction between cigarette smoking status and thienopyridine efficacy.

Genetic determinants of clopidogrel responsiveness in Koreans treated with drug-eluting stents

BACKGROUND

Variations of genes encoding cytochrome enzymes, drug transporters, and paraoxonase have recently been reported to be associated with clopidogrel response variability besides the well-known CYP2C19 loss-of-function (LOF) alleles. We determined whether newly reported genetic variations are associated with clopidogrel on-treatment platelet reactivity (OPR) in Korean patients.

METHODS

OPR was measured in 1264 consecutive patients who underwent percutaneous coronary intervention using the VerifyNowP2Y12 assay system and genotyping of PON-1 Q192R, ABCB1 C3435T, CYP1A2*1F, CYP2B6*6, CYP2C19*2, CYP2C19*3, CYP2C19*17, CYP3A4 (IVS10+12G>A), and CYP3A5*3 was performed. We applied two different cutoffs, i.e. 240 P2Y12 reaction units (PRU) and 253 PRU, to define high OPR.

RESULTS

Mean OPR of the entire population was 231±83 PRU. Genetic variations of ABCB1 and PON-1 genes as well as that of CYP1A2, 2B6, 3A4, and 3A5 were not associated with clopidogrel response variability. As for CYP2C19, patients were classified into 4 metabolism genotypes: 0.6% ultrarapid (UM), 40.3% extensive (EM), 48.8% intermediate (IM), and 10.3% poor metabolizers (PM). After adjustment for possible confounders, CYP2C19 metabolism genotype was associated with a significant increase in OPR: effect on OPR-difference: +27 PRU, p=0.015 for EM, +53 PRU, p<0.001 for IM, and +74 PRU, p=0.006 for PM compared with UM. In multivariable analysis, the CYP2C19 genotype was the only independent predictor of high-OPR among genetic variations using two different cutoffs.

CONCLUSIONS

Among genes postulated to be involved in clopidogrel metabolism, only the CYP2C19 genotype is associated with response variability and emerged as an independent predictor of high-OPR using two different cutoffs. PON-1 and ABCB1 genetic variants do not affect clopidogrel OPR in Korean patients.

Cigarette smoking is paradoxically associated with low mortality risk after acute myocardial infarction

BACKGROUND

Cigarette smoking has been shown to be associated with a decreased risk of death after acute myocardial infarction (AMI), which is also known as the "smokers' paradox." This study aimed to investigate the relationship between smoking and all-cause mortality after AMI.

METHODS

We extracted the data of patients who were hospitalized for AMI between November 2005 and September 2010 from nationwide multicenter prospective registries in Korea.

RESULTS

Among a total of 29,199 patients with AMI, 10,251 (42.3%) were current smokers, and 14,006 (57.7%) were nonsmokers. Current smokers were younger, more likely to be male, and had lower frequencies of hypertension, diabetes mellitus, dyslipidemia, and previous history of ischemic heart disease than nonsmokers. The initial presentation was less severe in terms of hemodynamic status, and angiography showed less complex coronary involvement in smokers. The overall mortality rate was 5.4% for current smokers and 9.9% for nonsmokers (hazard ratio [HR], 0.52; 95% confidence interval [CI], 0.47-0.58; p < .001). The gap in risk was attenuated after multivariable adjustment but remained statistically significant (HR, 0.85; 95% CI, 0.76-0.95; p = .005). Propensity score matching corroborated the results of reduced mortality among current smokers (6.7% vs. 7.6%; p = .005).

CONCLUSIONS

In this study, in which the patients received up-to-date treatment options, smoking was associated with a 48% decrease in the risk of all-cause mortality at 1 year after AMI.