Slow response to clopidogrel predicts low response

Influence of CYP450 Enzymes and ABCB1 Polymorphisms on Clopidogrel Response in Moroccan Patients with Acute Coronary Syndromes

Introduction

Clopidogrel is an antiplatelet prodrug primarily prescribed to prevent or treat acute coronary syndrome (ACS) or acute ischemic stroke (IS), polymorphisms of genes encoding cytochrome P-450 (CYP) and P-glycoprotein transporter, could affect the efficiency of clopidogrel absorption and biotransformation, especially during the first critical hours following its administration.

Methods

The present study was designed to investigate the potential association of clopidogrel responsiveness and 14 polymorphisms in the genes encoding the CYPs (CYP2C9, 2C19, 3A4, 3A5, 1A2, and 2B6), the ATP binding cassette subfamily B member 1 (ABCB1). Platelet aggregation activity was measured after 8h of 300mg clopidogrel administration for fifty-five ACS patients.

Results

There was no significant association between polymorphism of the studied CYPs and clopidogrel responsiveness (P>0.05). The frequency of the ABCB1 3435 T allele in clopidogrel non-responders was higher (78.9%) compared to responders (52.8%), but this difference was not significant (P=0.057). Demographic characteristics, comorbidities, concomitant treatments were not associated with clopidogrel response.

Discussion

There was no effect of the studied genetic variations and demographic factors on the platelet activity of clopidogrel in Moroccan ACS patients.

The association of body mass index with long-term clinical outcomes after ticagrelor monotherapy following abbreviated dual antiplatelet therapy in patients undergoing percutaneous coronary intervention: a prespecified sub-analysis of the GLOBAL LEADERS Trial

Background

The efficacy of antiplatelet therapies following percutaneous coronary intervention (PCI) may be affected by body mass index (BMI).

Methods and results

This is a prespecified subgroup analysis of the GLOBAL LEADERS trial, a prospective, multicenter, open-label, randomized controlled trial in an all-comer population undergoing PCI, comparing the experimental strategy (23-month ticagrelor monotherapy following 1-month dual antiplatelet therapy [DAPT]) with a reference regimen (12-month aspirin monotherapy following 12-month DAPT). A total of 15,968 patients were stratified by baseline BMI with prespecified threshold of 27 kg/m². Of those, 6973 (43.7%) patients with a BMI < 27 kg/m² had a higher risk of all-cause mortality at 2 years than those with BMI ≥ 27 kg/m² (adjusted HR 1.24, 95% CI 1.02–1.49). At 2 years, the rates of the primary endpoint (all-cause mortality or new Q-wave myocardial infarction) were similar between treatment strategies in either BMI group (p_interaction = 0.51). In acute coronary syndrome, however, the experimental strategy was associated with significant reduction of the primary endpoint compared to the reference strategy in patients with BMI < 27 kg/m² (HR 0.69, 95% CI 0.51–0.94), but not in the ones with BMI ≥ 27 kg/m² (p_interaction = 0.047). In chronic coronary syndrome, there was no between-group difference in the efficacy and safety of the two antiplatelet strategies.

Conclusions

Overall, BMI did not influence the treatment effect seen with ticagrelor monotherapy; however, a beneficial effect of ticagrelor monotherapy was seen in ACS patients with BMI < 27 kg/m².

Trial registration

The trial has been registered with ClinicalTrials.gov, Number NCT01813435.

Graphic abstract

Electronic supplementary material

The online version of this article (10.1007/s00392-020-01604-1) contains supplementary material, which is available to authorized users.

Smoking and outcomes following guided de-escalation of antiplatelet treatment in acute coronary syndrome patients: a substudy from the randomized TROPICAL-ACS trial

Aims

Prior analyses disclosed variations in antiplatelet drug response and clinical outcomes between smokers and non-smokers, thus the safety and efficacy of any dual antiplatelet therapy (DAPT) de-escalation strategy may differ in relation to smoking status. Hence, we assessed the impact of smoking on clinical outcomes and adenosine diphosphate-induced platelet aggregation following guided de-escalation of DAPT in invasively managed acute coronary syndrome (ACS) patients.

Methods and results

The multicentre TROPICAL-ACS trial randomized 2610 biomarker-positive ACS patients 1:1 to standard treatment with prasugrel for 12 months (control group) or a platelet function testing guided de-escalation of DAPT. Current smokers (n = 1182) showed comparable event rates between study groups [6.6% vs. 6.6%; hazard ratio (HR) 1.0, 95% confidence interval (CI) 0.64–1.56, P &gt; 0.99]. In non-smokers (n = 1428), a guided DAPT de-escalation was associated with a lower 1-year incidence of the primary endpoint [cardiovascular death, myocardial infarction, stroke, or bleeding ≥ Grade 2 according to Bleeding Academic Research Consortium (BARC) criteria] compared with control group patients (7.9% vs. 11.0%; HR 0.71, 95% CI 0.50–0.99, P = 0.048). This reduction was mainly driven by a lower rate of BARC ≥ Grade 2 bleedings (5.2% vs. 7.7%; HR 0.68, 95% CI 0.45–1.03, P = 0.066). There was no significant interaction of smoking status with treatment effects of guided DAPT de-escalation (Pint = 0.23). Adenosine diphosphate-induced platelet aggregation values were higher in current smokers [median 28 U, interquartile range (IQR: 20–40)] vs. non-smoker [median 24 U (16–25), P &lt; 0.0001] in the control group and in current smokers [median 42 U, IQR (27–68)] vs. non-smoker [median 37 U, IQR (25–55), P &lt; 0.001] in the monitoring group.

Conclusion

Guided DAPT de-escalation appears to be equally safe and effective in smokers and non-smokers. Regardless of smoking status and especially for those patients deemed unsuitable for 1 year of potent platelet inhibition this DAPT strategy might be used as an alternative antiplatelet treatment regimen.

Platelet reactivity inhibition following ticagrelor loading dose in patients undergoing percutaneous coronary intervention for acute coronary syndrome

BACKGROUND

Ticagrelor induces more potent platelet reactivity (PR) inhibition with reduced interindividual variability compared to clopidogrel. Although on-clopidogrel PR was shown to correlate with ischemia and bleeding events, no study has investigated the relationship between on-ticagrelor PR and outcome.

OBJECTIVES

We aimed to evaluate the relationship between on-ticagrelor PR, assessed by the vasodilator-stimulated phosphoprotein index (VASP), and thrombotic and bleeding events in patients with acute coronary syndrome (ACS) treated by percutaneous coronary intervention (PCI).

METHODS

We performed a prospective, multicenter observational study on patients treated with PCI for ACS. The VASP index was used to assess PR after ticagrelor loading dose (LD). The primary endpoint was the link between major adverse cardiovascular events (MACE) and PR.

RESULTS

Among the 530 patients with ACS included, 183 (34.5%) were admitted for ST elevation myocardial infarction. We observed high potency and limited interindividual variability after the ticagrelor LD (VASP 19.1% ± 16.6%). At 1 month, 21 (3.8%) MACE and 29 (5.5%) bleedings ≥ 2 according to the Bleedings Academic Research Consortium (BARC) scale were recorded. Neither MACE nor bleeding was associated with PR (P = .34 and P = .78, respectively). However, there was a strong association between PR and the occurrence of definite acute stent thrombosis (P = .03). Platelet reactivity was the only factor associated with acute definite stent thrombosis.

CONCLUSION

In patients receiving a ticagrelor LD while undergoing PCI for ACS, PR using the VASP did not predict MACE or bleeding, but it was significantly associated with the occurrence of definite acute stent thrombosis.

The effect of smoking on residual platelet reactivity to clopidogrel: a systematic review and meta-analysis

Cigarette smoking is an important cardiovascular risk factor, causing morbidity and mortality. There are many original studies on the impact of smoking, but its influence on platelet ADP-P2Y12 receptor inhibitors lack consistency. Thus, we conducted a systematic review and meta-analysis of already existing data/studies to further explore this issue. PubMed, Web of science, EMBASE, Clinical Trials, and the Cochrane Library were searched from inception to March 2018. Studies investigating the residual platelet reactivity categorized by smoking status and patients treated with platelet ADP-P2Y12 receptor inhibitors qualified the inclusion criteria. The primary outcome was P2Y12 reaction unit (PRU) value measured by VerifyNow P2Y12 assay, compared with different smoking status in ADP-P2Y12 receptor inhibitors treatment groups. Secondary outcome was post-treatment with 5 μmol/L ADP-inhibition of platelet aggregation (ADP-IPA) measured by light transmittance aggregometry (LTA). Of the 4954 citations retrieved, 12 studies involving 16 296 patients with acute coronary syndrome and/or stent deployment using platelet ADP-P2Y12 receptor inhibitors were included for meta-analysis. Pooled analysis revealed that PRU values of current smokers were 25.70 lower than nonsmokers (95% CI -38.81 to -12.60, p = 0.0001), getting better effects of antiplatelet treatment. In the smoking extent subgroup analysis, patients smoking >10 cigarettes/day shown about 46.49 lower of PRU values than patients smoking <10 cigarettes/day (p < 0.00001). Racial subgroup analyses found that smokers had increased platelet inhibition in the Caucasian population. Further, pooled analysis of ADP-IPA values for 1658 patients from five studies showed a significantly lower residual platelet reactivity in current smokers compared to that in nonsmokers (MD = -4.19; 95% CI -6.55 to -1.83; p = 0.0005). This systematic review and meta-analysis suggested that smokers have increased platelet inhibition and lower aggregation in response to clopidogrel than nonsmokers. These residual platelet reactivity observations may help to explain differential clinical outcomes in smokers vs. nonsmokers in large scale clinical trials.

Genetic variability in response to clopidogrel therapy and its clinical implications

This article concentrates on individual genetic differences responsible for variations of action of clopidogrel, which have been found to be partially responsible for increased cardiovascular events in patients with coronary artery disease under dual antiplatelet therapy. According to these results, genotyping for the relevant gene polymorphisms, especially for the CYP2C19 loss-of-function alleles, has been discussed to be an effective method of individualising and optimising clopidogrel treatment. However, due to the facts that 1) there are no prospective studies demonstrating a clinical benefit of personalising antiplatelet therapy based on genotyping; 2) CYP2C19 polymorphisms account for only approximately 12% of variability in clopidogrel platelet response; 3) the positive predictive value of CYP2C19 loss-of-function polymorphisms for cardiovascular events in patients with acute coronary syndrome undergoing percutaneous coronary intervention is only approximately 12% – 20%; 4) it is likely that other clinical factors and risk constellations might be of greater clinical importance; and 5) it is unknown whether a specific genetic polymorphism is capable of influencing outcome for the individual patient; genetic profiling cannot be recommended for routine use at present but will remain of considerable scientific interest.

Identification of poor response to P2Y12 inhibitors in ACS patients with a new ELISA-based vasodilator-associated stimulated phosphoprotein (VASP) phosphorylation assay

A new ELISA technique has been developed to measure the vasodilator-associated stimulated phosphoprotein (VASP) platelet reactivity index (PRI) in clopidogrel-treated patients. This technique has not been evaluated in acute coronary syndrome (ACS) patients or in prasugrel-treated patients. We assessed the accuracy of ELISA-VASP to identify high on-treatment platelet reactivity (HPR) in ACS patients in comparison with established platelet function tests. Platelet reactivity was measured in 240 ACS patients treated with clopidogrel (75 or 150 mg) or prasugrel (5 or 10 mg) using flow cytometry (FC-VASP) and the ELISA-VASP technique, light transmission aggregometry (LTA) and VerifyNow-P2Y12 assay (VN-P2Y12). When using the ELISA-VASP PRI, the rate of patients with HPR in the overall ACS population was 15.5%, including a 27% rate in clopidogrel-treated patients and a 4% rate in prasugrel-treated patients. There was a strong correlation between ELISA-VASP PRI and FC-VASP PRI (r = 0.83, r2 = 0.68 p < 0.0001) with an area under the receiver-operating characteristics (ROC) curve to identify HPR (VASP-PRI >50% with FC-VASP) of 0.94, p<0.0001. The threshold of 60% for ELISA-VASP PRI provided the best accuracy (likelihood ratio= 23.67) to identify patients with HPR when compared to FC-VASP, LTA or VN-P2Y12 assays. In conclusion, ELISA-VASP is a fast, easy-to-use and specific test to identify HPR in ACS patients on thienopyridines. A 60% threshold value displays the best accuracy to identify HPR in these patients.

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.

Dual antiplatelet therapy: optimal timing, management, and duration

Platelet activation and aggregability play a key role in the genesis of arterial thrombus secondary to plaque rupture. For coronary patients, inhibition of platelet function is crucial to decrease the rate of major adverse cardiac events but may expose them to excess bleeding risk. Switching P2Y12 inhibitors is common, yet the clinical consequences are unknown. The aim of this review is to provide an overview of the evidence from randomized, clinical trials and epidemiological studies, with a focus on the optimal duration of dual antiplatelet therapy (DAPT) and appropriate agent and dose selection. The report discusses the latest evidence regarding switching therapies during DAPT, the potential benefits of a personalized strategy, management of the preoperative period, and other clinical perspectives in this complex and rapidly changing field. Ongoing trials will be useful to answer to some important unresolved questions.

Higher body weight patients on clopidogrel maintenance therapy have lower active metabolite concentrations, lower levels of platelet inhibition, and higher rates of poor responders than low body weight patients

Body weight is a predictor of clopidogrel response. However, no prospective studies have compared pharmacodynamic (PD) and pharmacokinetic (PK) data based on body weight. We compared PD and PK effects of clopidogrel 75 mg in low body weight (LBW, <60 kg) and higher body weight (HBW, ≥60 kg) patients with stable coronary artery disease. LBW (n = 34, 56.4 ± 3.7 kg) and HBW (n = 38, 84.7 ± 14.9 kg) aspirin-treated patients received clopidogrel 75 mg for 10-14 days. The area under the concentration-time curve of active metabolite (Clop-AM) calculated through the last quantifiable concentration up to 4 h postdose, AUC(0-tlast), was calculated by noncompartmental methods. Light transmission aggregometry (LTA) (maximum platelet aggregation and inhibition of platelet aggregation to 20 μM adenosine diphosphate (ADP), and residual platelet aggregation to 5 μM ADP), VerifyNow(®) P2Y12 reaction units (PRU), and vasodilator-associated stimulated phosphoprotein phosphorylation platelet reactivity index (VASP-PRI) were performed. Mean AUC(0-tlast) was lower in HBW than LBW patients: 12.8 versus 17.9 ng h/mL. HBW patients had higher platelet reactivity as measured by LTA (all p ≤ 0.01), PRU (207 ± 68 vs. 152 ± 57, p < 0.001), and VASP-PRI (56 ± 18 vs. 39 ± 17, p < 0.001). More HBW patients exhibited high on-treatment platelet reactivity (HPR) using PRU (35 vs. 9%) and VASP-PRI (65 vs. 27%). Body weight correlated with PRU and VASP-PRI (both p < 0.001), and inversely with log transformed AUC(0-tlast) (p < 0.001). In conclusion, HBW patients had lower levels of Clop-AM, and higher platelet reactivity and rates of HPR than LBW subjects, contributing to their suboptimal response to clopidogrel.

Reappraisal of thienopyridine pretreatment in patients with non-ST elevation acute coronary syndrome: a systematic review and meta-analysis

OBJECTIVE

To investigate the effect of pretreatment with P2Y12 receptor inhibitors compared with no pretreatment on efficacy and safety of treatment of non-ST elevation acute coronary syndrome (ACS).

DATA SOURCES

Two reviewers independently searched Medline, Embase, Cochrane Controlled Trials, and BioMed Central databases for randomized placebo controlled trials and observational studies from August 2001 to March 2014.

STUDY ELIGIBILITY

Studies must have reported both all-cause mortality (primary efficacy endpoint) and major bleeding (safety endpoint) outcomes.

DATA EXTRACTION

Data on sample size, characteristics, drug dose and delay of administration, and outcomes were independently extracted and analyzed.

DATA SYNTHESIS

A random-effect model was applied. The analysis was performed (i) in all patients independently of the management strategy and (ii) only in patients undergoing percutaneous coronary intervention.

RESULTS

Of the 393 titles identified, seven (four randomized controlled trials, one observational analysis from a randomized controlled trial, and three observational studies) met the inclusion criteria. No study was identified for ticagrelor or cangrelor, and analyses were thus limited to thienopyridines. A total of 32,383 non-ST elevation ACS patients were included, 18,711 coming from randomized controlled trials. Of these, 55% underwent percutaneous coronary intervention (PCI). Pretreatment was not associated with a significant lower risk of mortality in all patients (odds ratio 0.90 (95% confidence interval 0.75 to 1.07), P=0.24), in particular when considering only the randomized controlled trials (odds ratio 0.90 (0.71 to 1.14), P=0.39). Similar results were observed in the cohort of patients undergoing PCI. A significant 30-45% excess of major bleeding was consistently observed in all patients (odds ratio 1.32 (1.16 to 1.49), P<0.0001) and in those undergoing PCI, as well as in the subset analyses of randomized controlled trials of these two cohorts of patients. There was a reduction in major adverse cardiovascular events in the analysis of all patients (odds ratio 0.84 (0.72 to 0.98), P=0.02), driven by the old clopidogrel studies (CURE and CREDO), but the difference was not significant for the cohort of patients undergoing PCI. Stent thrombosis, stroke, and urgent revascularization did not differ between groups (pretreatment v no pretreatment). The results were consistent for both thienopyridines and confirmed in sensitivity analyses.

LIMITATIONS

Analysis was not performed on individual patient's data.

CONCLUSION

In patients presenting with non-ST elevation ACS, pretreatment with thienopyridines is associated with no significant reduction of mortality but with a significant excess of major bleeding no matter the strategy adopted, invasive or not. Our results do not support a strategy of routine pretreatment in patients with non-ST elevation ACS.

Severe left ventricular systolic dysfunction is independently associated with high on-clopidogrel platelet reactivity

OBJECTIVE

The purpose of the present study was to investigate the association between left ventricular systolic function and the response to clopidogrel.

METHODS

The efficacy of clopidogrel was measured by the vasodilator-stimulated phosphoprotein phosphorylation 20 ± 4 h after 600 mg of clopidogrel. High on-clopidogrel platelet reactivity (HCPR) was defined as a platelet reactivity index (PRI) ≥50%. The 30-day combined incidence of death, non-fatal acute coronary syndrome, re-percutaneous coronary intervention (PCI), stent thrombosis, and stroke was also investigated.

RESULTS

The study group consisted of 519 patients undergoing PCI. The values (mean and 95% confidence interval) of the PRI were as follows: 40.4% (37.8-43.0) in patients with left ventricular ejection fraction (LVEF) >50%, 42.4% (39.3-45.6) in patients with LVEF 35-50%, and 46.7% (40.6-52.9) in patients with LVEF <35% (p = 0.013). The proportions of patients with HCPR were 35.9% in patients with LVEF ≥35 and 51.9% in patients with LVEF <35% (p = 0.022). After adjustment for variables that significantly influenced clopidogrel efficacy, LVEF <35% was found to be independently associated with HCPR (p = 0.039). The 30-day combined clinical endpoint occurred in 18% of patients with LVEF <35% and in 7.3% of patients with LVEF ≥35% (p = 0.026). The 30-day incidence of all-cause mortality was 14% in patients with LVEF <35 and 1.0% in patients with LVEF ≥35% (p < 0.001).

CONCLUSION

An LVEF <35% was found to be independently associated with HCPR.

Faster, higher, stronger? Evidence for formulation and efficacy for ibuprofen in acute pain

A Cochrane review of ibuprofen in acute pain suggested that rapidly absorbed formulations of salts, or features to speed absorption, provided better analgesia than standard ibuprofen as the free acid. We examined several lines of evidence to investigate what benefit derived from fast-acting formulations. A systematic review of the kinetics of oral ibuprofen (30 studies, 1015 subjects) showed that median maximum plasma concentrations of fast-acting formulations occurred before 50 min (29-35 min for arginine, lysine, and sodium salts) compared with 90 min for standard formulations. An updated analysis of clinical trials (over 10,000 patients) showed that fast-acting formulations produced significantly better analgesia over 6h and fewer remedications than standard formulations in both indirect and direct comparisons. In dental studies, 200-mg fast-acting ibuprofen (number needed to treat 2.1; 95% confidence interval 1.9-2.4) was as effective as 400 mg standard ibuprofen (number needed to treat 2.4; 95% confidence interval 2.2-2.5), with faster onset of analgesia. Individual patient data analysis in dental pain demonstrated a strong correlation between more rapid reduction of pain intensity over 0-60 min and better pain relief over 0-6h. Rapid initial reduction of pain intensity was also linked with reduced need for remedication. Fast-acting formulations of ibuprofen demonstrated more rapid absorption, faster initial pain reduction, good overall analgesia in more patients at the same dose, and probably longer-lasting analgesia, but with no higher rate of patients reporting adverse events. Achieving a better analgesic effect with fast-acting nonsteroidal anti-inflammatory drug formulations has important implications for safety. Formulation chemistry is of potential importance for analgesics.

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.

Impact of smoking on antiplatelet effect of clopidogrel and prasugrel after loading dose and on maintenance therapy

BACKGROUND

Pharmacodynamic studies reported an amplified on-clopidogrel platelet inhibition in smokers potentially caused by an increased metabolic drug activation via induction of cytochrome P450 1A2. The aims of this analysis were to evaluate the impact of smoking on the antiplatelet effect of clopidogrel and prasugrel and to test the potential interaction of smoking with the treatment effect of these drugs.

METHODS

A variety of platelet function results was analyzed from 2 large cohorts of patients undergoing coronary intervention after loading with clopidogrel 600 mg (n = 2,533 and n = 1,996), a cohort of patients undergoing dose adaptation from 75 to 150 mg according to response to clopidogrel (n = 117) and a crossover trial comparing clopidogrel 150 mg with prasugrel 10 mg (n = 87). Linear regression analyses were used to test the impact of smoking on platelet function and to identify independent predictors of on-treatment platelet reactivity. The potential interaction of smoking with the clinical effect of clopidogrel versus prasugrel was analyzed in the TRITON-TIMI 38 cohort (n = 13,608).

RESULTS

No significant association of smoking with platelet reactivity on clopidogrel was seen in unadjusted and adjusted analyses. The variables most consistently associated with on-clopidogrel platelet function were age, sex, diabetes, and body mass index. There was no significant interaction of smoking status at presentation with the clinical efficacy of prasugrel versus clopidogrel (P for interaction = .39).

CONCLUSIONS

Smoking does not impact on platelet reactivity in patients after loading or on different maintenance doses of clopidogrel. The clinical treatment effect of clopidogrel versus prasugrel is not affected by smoking status at presentation.