Comparison Between Aspirin and Clopidogrel in Secondary Stroke Prevention Based on Real-World Data

Current and potentially novel antithrombotic treatment in acute ischemic stroke

Acute ischemic stroke (AIS) is the most common type of stroke and requires immediate reperfusion. Current acute reperfusion therapies comprise the administration of intravenous thrombolysis and/or endovascular thrombectomy. Although these acute reperfusion therapies are increasingly successful, optimized secondary antithrombotic treatment remains warranted, specifically to reduce the risk of major bleeding complications. In the development of AIS, coagulation and platelet activation play crucial roles by driving occlusive clot formation. Recent studies implicated that the intrinsic route of coagulation plays a more prominent role in this development, however, this is not fully understood yet. Next to the acute treatments, antithrombotic therapy, consisting of anticoagulants and/or antiplatelet therapy, is successfully used for primary and secondary prevention of AIS but at the cost of increased bleeding complications. Therefore, better understanding the interplay between the different pathways involved in the pathophysiology of AIS might provide new insights that could lead to novel treatment strategies. This narrative review focuses on the processes of platelet activation and coagulation in AIS, and the most common antithrombotic agents in primary and secondary prevention of AIS. Furthermore, we provide an overview of promising novel antithrombotic agents that could be used to improve in both acute treatment and stroke prevention.

[Secondary prophylaxis of ischemic stroke]

The secondary prophylaxis of ischemic stroke provides an enormous therapeutic potential due to the high frequency of recurrent thrombembolic events and the exceptional importance of modifiable cardiovascular risk factors for the individual risk of stroke. In this respect, anti-thrombotic, interventional and surgical treatment options must be selected based on the respective etiology. Furthermore, meticulous optimization of risk factors is essential for effective long-term care. Close interdisciplinary and intersectoral collaboration is crucial, especially in the long-term treatment.

Antiplatelet Treatment Patterns and Outcomes for Secondary Stroke Prevention in the United Kingdom

INTRODUCTION

Stroke is a leading cause of death and disability worldwide. Antiplatelet therapies are recommended to reduce the risk of recurrent stroke in patients with ischemic stroke/transient ischemic attack (IS/TIA). This study evaluated outpatient antiplatelet treatment patterns and outcomes for secondary stroke prevention (SSP) among UK adults without atrial fibrillation who were hospitalized for IS/TIA.

METHODS

This retrospective observational study utilized data from the UK Clinical Practice Research Datalink linked with Hospital Episode Statistics data (01/01/2011-30/06/2019). Treatment patterns included type and duration of treatments. Treatment outcomes included IS, myocardial infarction, major bleeding, and cardiovascular-related and all-cause mortality. Descriptive statistics were reported.

RESULTS

Of 9270 patients, 13.9% (1292) might not receive antithrombotic therapy within 90 days of hospital discharge. Of 7978 patients who received antiplatelet therapies, most used clopidogrel (74.8%) or aspirin (16.7%) single antiplatelet therapy and clopidogrel + aspirin dual antiplatelet therapy (DAPT, 5.9%). At 1-year post-hospitalization, 36.9, 43.3, and 35.1% of those receiving these treatments discontinued them, respectively, and of the patients initiating DAPT, 62.3% switched to single antiplatelet therapy. At 1-year post-discharge, the incidence rate (per 100 person-years) of IS, myocardial infarction, major bleeding, cardiovascular-related mortality, and all-cause mortality among the treated were 6.5, 0.7, 4.1, 5.0, and 7.3, respectively, and among the untreated were 14.9, 0.7, 8.6, 28.1, and 39.8, respectively.

CONCLUSIONS

In the United Kingdom, 13.9% of patients hospitalized for stroke might not have any antiplatelet treatment to prevent secondary stroke; among the treated, clopidogrel, aspirin, and DAPT were commonly used. These study findings suggest that improved anti-thrombotic therapies for long-term SSP treatment are needed, which may lead to higher treatment and persistence rates and, therefore, improved outcomes in this population.

Antiplatelet treatment patterns and outcomes of secondary stroke prevention in the United States

Objective

Patients who have an ischemic stroke (IS) or transient ischemic attack (TIA) are at risk of having a secondary stroke. Single antiplatelet therapy (SAPT) or dual antiplatelet therapy (DAPT) may be recommended for secondary stroke prevention (SSP), depending on severity and etiology. This study evaluated outpatient antiplatelet treatment patterns for SSP and outcomes after first hospitalization for IS/TIA among adults without atrial fibrillation in the United States.

Materials and methods

This retrospective observational study utilized data from an adjudicated administrative health claims database. Eligible patients had an imputed National Institutes of Health Stroke Scale index event score ≤7. Over-the-counter medication use (eg, aspirin) was not captured.

Results

Of 154,273 patients, 41,622 (27%) were prescribed antiplatelet therapy within 90 days of the event; 93.8% received SAPT, 6.1% received DAPT. The first line of antiplatelet therapy after discharge was started a mean of 17.0 days after the event; mean treatment duration was 61.9 days. The incidence rate for secondary IS was 5.53, 2.03, and 1.17 per person-year 90-days, 1-year, and 3-years following treatment initiation, respectively. Among patients matched for demographic and clinical characteristics, the risk of secondary IS was increased with DAPT versus SAPT (hazard ratio [95% CI]: 1.27 [1.20-1.34]; p < 0.0001).

Conclusions

Many patients were not prescribed or discontinued antiplatelet therapy within 90 days of hospitalization for IS/TIA and, in most cases, prescriptions were not compliant with SSP consensus guidelines. Patients remained at risk for IS, which was highest within 90 days. More effective strategies for SSP are needed to improve outcomes in this patient population.

Clopidogrel Monotherapy versus Aspirin Monotherapy in Patients with Established Cardiovascular Disease: Systematic Review and Meta-Analysis

BACKGROUND

 There is no clear consensus on whether aspirin offers better outcomes in terms of secondary cardiovascular disease prevention compared with clopidogrel.

OBJECTIVE

 The aim of the study was to compare the safety and efficacy of clopidogrel versus aspirin in patients with established cardiovascular disease.

METHODS

 A systematic review of MEDLINE (via PubMed), Scopus, and Cochrane Library databases (last search date: August 28, 2021) was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) statement for randomized control trials (RCTs) of clopidogrel versus aspirin as monotherapy in patients with established cardiovascular disease. Random-effects meta-analyses were performed.

RESULTS

 Five RCTs incorporating 26,855 patients (clopidogrel: 13,426; aspirin: 13,429) were included. No statistically significant difference was observed between clopidogrel and aspirin in terms of all-cause mortality (odds ratio [OR]: 1.01 [95% confidence interval, CI: 0.91-1.13]; p = 0.83), ischemic stroke (OR: 0.87 [95% CI: 0.71-1.06]; p = 0.16), and major bleeding rates (OR: 0.77 [95% CI: 0.56-1.06]; p = 0.11). Patients receiving clopidogrel had borderline lower risk for major adverse cardiovascular events (MACE) (OR: 0.84 [95% CI: 0.71-1.00]; p = 0.05) and lower risk for nonfatal myocardial infarction (OR: 0.83 [95% CI: 0.71-0.97]; p = 0.02, relative risk reduction = 16.9%, absolute risk reduction = 0.5%, number needed to treat = 217 for a mean period of 20 months) compared with patients receiving aspirin.

CONCLUSION

 In patients with established cardiovascular disease, clopidogrel was associated with a 17% relative-risk reduction for nonfatal MI, borderline decreased risk for MACE, and similar risk for all-cause mortality, stroke, and major bleeding compared with aspirin.

PROTOCOL REGISTRATION

 PROSPERO CRD42021283866.

Outcomes of a multi-ethnic Asian population on combined treatment with clopidogrel and omeprazole in 12,440 patients

Omeprazole is commonly co-prescribed with clopidogrel. Clopidogrel requires bio-activation by cytochrome P450 CYP2C19. Omeprazole may reduce clopidogrel's antithrombotic efficacy by inhibiting CYP2C19. Studies in Caucasians receiving omeprazole with clopidogrel showed no significant increase in death and myocardial infarction with this drug-drug interaction. There are limited large-scale studies in Asians, who may have a greater prevalence of CYP2C19 loss-of-function polymorphisms. A single centre retrospective cohort study was undertaken based on a review of medication records and prescription data. Patients prescribed clopidogrel from 2009 to 2012 were followed-up with until December 2012 (median:29 months). The primary outcome was all-cause mortality and secondary outcomes were myocardial infarction (MI), cerebrovascular accidents, and subsequent coronary interventions. Of 12,440 patients prescribed clopidogrel, 62%(n = 7714) were on omeprazole (63.8% Chinese, 13.9% Malay, 12.4% Indian, 10.0% others), and 38%(n = 4726) were not on omeprazole or other proton pump inhibitors (62.6% Chinese, 13.5% Malay, 10.7% Indian, 13.2% others). Mortality after co-prescription occurred in 14.3%(n = 1101) of patients, compared to 6.3%(n = 300) of patients prescribed clopidogrel only. Multivariate analysis using propensity score adjusted analysis showed no significant increase in all-cause mortality with co-prescription (adjusted hazards ratio [AHR] 1.13, [95%CI 0.95-1.35]). Patients on co-prescription had a higher risk of subsequent MI (16% vs 3.8%; AHR 2.03 [95%CI 1.70-2.44]), but not of cerebrovascular accidents (5.0% vs 2.0%; AHR 0.98 [95%CI 0.76-1.27]) or coronary interventions (1.7% vs 0.7%; AHR 1.28 [95%CI 0.83-1.96]). The risk of a subsequent MI was higher in the Malay (AHR 2.43 [95%CI 1.68-3.52]) and Chinese (AHR 2.06 [95%CI 1.63-2.60]) population as compared to the Indian (AHR 1.56 [95%CI 1.06-2.31]) population. In conclusion, the use of clopidogrel with omeprazole is associated with an increased risk of MI, but not mortality or stroke, in this multi-ethnic Asian population. These risks appear to vary among different ethnic groups.

Cost Effectiveness of Genotype-Guided Antiplatelet Therapy in Asian Ischemic Stroke Patients: Ticagrelor as an Alternative to Clopidogrel in Patients with CYP2C19 Loss of Function Mutations

BACKGROUND

Patients with ischemic stroke are often treated with clopidogrel monotherapy as part of secondary stroke prevention. The prevalence of loss of function (LOF) mutations in the CYP2C19 gene is higher in Asians than in Western populations. Patients with loss of function (LOF) mutations are at risk for poorer secondary outcomes when prescribed clopidogrel.

OBJECTIVE

We aimed to determine the cost effectiveness of genotype-guided antiplatelet therapy in an Asian population with the aim of prescribing ticagrelor as an alternative to patients with LOF mutations.

METHODS

Markov models were developed to look at the cost effectiveness of genetic testing of CYP2C19, with patients who screened positive for LOF alleles being switched to ticagrelor compared to universal clopidogrel treatment. Effect ratios were obtained from the literature and incidence rates and costs were obtained from the national data published by the Singapore Ministry of Health. Lifetime costs and quality-adjusted life-years (QALYs) were calculated. The primary endpoints were the incremental cost-effectiveness ratios (ICERs).

RESULTS

The prevalence of the LOF mutations was 61% in the population, with 65% of ethnic Chinese, 60% of ethnic Indian, and 53% of ethnic Malay patients having LOF mutations. Based on this prevalence, the overall ICER of genetic testing was S$33,839/QALY with ICERS of S$30,755/QALY, S$33,177/QALY, and S$41,470/QALY for Chinese, Indians, and Malays, respectively.

CONCLUSION

This study suggests that it is cost effective to screen for LOF mutations in the CYP2C19 gene in ischemic stroke populations, with ticagrelor as a substitute for clopidogrel in those with LOF mutations.

Body weight, CYP2C19, and P2Y12 receptor polymorphisms relate to clopidogrel resistance in a cohort of Chinese ischemic stroke patients with aspirin intolerance

PURPOSE

Dual antiplatelet therapy (DAT) with clopidogrel and aspirin is not suitable for clopidogrel resistance (CR) patients with aspirin intolerance. To investigate the prevalence of CR in patients with aspirin intolerance after ischemic stroke (IS) and to assess the relationship between CR and CYP2C19, P2Y12 receptor genotypes in patients with aspirin intolerance after IS.

METHODS

We enrolled 126 IS patients with aspirin intolerance from Han Chinese in Shangqiu from January 2016 to November 2018. All IS patients with aspirin intolerance were treated with clopidogrel for 7 days. Adenosine diphosphate-induced platelet inhibition rate was measured by thrombelastography (TEG) mapping assay. The SNPs CYP2C19*2, CYP2C19*3, and P2Y12 receptor (52 G >T) were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Binary logistic regression analyses were performed using SPSS version 20.0.

RESULTS

The prevalence of CR in patients with aspirin intolerance after IS was approximately 31.0%. Multivariate regression analysis showed that body weight (OR 1.091 (95% CI 1.031-1.155), p = 0.003), CYP2C19 phenotype intermediate metabolizer (IM) (OR 3.820 (95% CI 1.021-14.288), p = 0.046), and CYP2C19 phenotype poor metabolizer (PM) (OR 14.481 (95% CI 2.791-75.129), p = 0.001) significantly increased the risk of CR and P2Y12 receptors (52 G >T) (OR 3.498 [95% CI 1.251-9.784], p = 0.017) increased the risk of CR.

CONCLUSIONS

The patients with high body weight, the CYP2C19 phenotypes, and P2Y12 receptor (52 G >T) variant alleles are at risk of CR during clopidogrel treatment in Chinese IS patients with aspirin intolerance. The higher body weight and relevant polymorphisms may help to predict CR in Chinese IS patients with aspirin intolerance.

Efficacy and safety of clopidogrel and aspirin do not differ in patients with stable ischemic stroke

BACKGROUND

The current study compared the efficacy and safety of clopidogrel vs aspirin in the secondary prevention of ischemic stroke (IS).

METHODS

We included patients from the Taiwan National Health Insurance Research Database who were aged between 20 and 80 years, had their first ever IS, had no diagnosis of atrial fibrillation, and had not used an oral anticoagulant before the index IS between 2002 and 2010. We excluded patients who died or were admitted to a hospital due to acute myocardial infarction, recurrent IS, or major bleeding within 3 months of IS. Patients were then classified into clopidogrel as aspirin users. Propensity score matching was adopted to select clopidogrel and aspirin groups with similar baseline characteristics (n = 8457 vs 16,914, mean follow-up period of 2.1 years and 1.9 years, respectively). Conditional Cox proportional hazard regression was used to compare risks of all-cause death, cardiovascular death, recurrent stroke, acute myocardial infarction, and major bleeding in clopidogrel users and aspirin users.

RESULTS

The risks of all-cause death, cardiovascular death, recurrent stroke, and acute myocardial infarction did not differ between clopidogrel and aspirin users. Subgroup analyses revealed that the results were consistent regardless of age, disease severity, or comorbidity.

CONCLUSION

According to real-world data, the efficacy and safety of clopidogrel and aspirin for secondary prevention of stable IS did not differ.

Aspirin Versus Clopidogrel Monotherapy for the Secondary Prevention of Recurrent Cerebrovascular Attack Following Previous Ischemic Stroke in Patients with Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis

INTRODUCTION

Type 2 diabetes mellitus (T2DM) and stroke are two different diseases, but have many aspects in common. Aspirin is recommended as an initial treatment for the secondary prevention of recurrent ischemic stroke in patients with T2DM. However, clopidogrel is an oral antiplatelet drug that might be another choice in case of aspirin intolerance. In this analysis, we aimed to systematically compare aspirin versus clopidogrel monotherapy for the secondary prevention of recurrent cerebrovascular attack following previous ischemic stroke in patients with T2DM.

METHODS

Online medical databases including Web of Science, MEDLINE, Cochrane central, EMBASE and http://www.ClinicalTrials.com were searched for published articles that satisfied the inclusion and exclusion criteria of this study. Recurrent stroke, fatal stroke, cerebral hemorrhage, myocardial infarction and mortality were considered the main end points in these patients with T2DM. RevMan 5.3 software was used to statistically analyze the data representing each subgroup. Risk ratios (RRs) with 95% confidence intervals (CIs) were used to represent the results following analysis.

RESULTS

A total of 9218 participants with T2DM who were previously affected by ischemic stroke were included in this analysis, whereby 4917 were assigned to aspirin and 4301 to clopidogrel. This current analysis showed that there was no significant difference in recurrent stroke rate (RR: 0.79, 95% CI: 0.61-1.02; P = 0.07) observed with aspirin versus clopidogrel in these patients with T2DM. The risk of fatal stroke (RR: 0.88, 95% CI: 0.39-1.98; P = 0.76), cerebral hemorrhage (RR: 0.65, 95% CI: 0.38-1.11; P = 0.12), myocardial infarction (RR: 0.88, 95% CI: 0.43-1.79; P = 0.71) and mortality (RR: 1.07, 95% CI: 0.90-1.27; P = 0.44) were also similarly manifested.

CONCLUSION

Clopidogrel monotherapy was neither inferior nor superior to aspirin monotherapy for the secondary prevention of recurrent cerebrovascular attack following previous ischemic stroke in patients with T2DM. Hence, clopidogrel or aspirin monotherapy is equally safe and effective in these patients with T2DM.

Benefits and Risks of Clopidogrel vs. Aspirin Monotherapy after Recent Ischemic Stroke: A Systematic Review and Meta-Analysis

Aim

Though combination of clopidogrel added to aspirin has been compared to aspirin alone in patients with stroke or transient ischemic attack, limited data exists on the relative efficacy and safety between clopidogrel and aspirin monotherapy in patients with a recent ischemic stroke. We aimed to compare clopidogrel versus aspirin monotherapy in this population.

Methods

PubMed, Embase, and CENTRAL databases were searched from inception to May 2018 to identify clinical trials and observational studies comparing clopidogrel versus aspirin for secondary prevention in patients with recent ischemic stroke within 12 months. Pooled effect estimates were calculated using a random effects model and were reported as risk ratios with 95% confidence intervals.

Results

Five studies meeting eligibility criteria were included in the analysis. A total of 29,357 adult patients who had recent ischemic stroke received either clopidogrel (n = 14, 293) or aspirin (n = 15, 064) for secondary prevention. Pairwise meta-analysis showed a statistically significant risk reduction in the occurrence of major adverse cardiovascular and cerebrovascular events (risk ratio 0.72 [95% CI, 0.53–0.97]), any ischemic or hemorrhagic stroke (0.76 [0.58, 0.99), and recurrent ischemic stroke (0.72 [0.55, 0.94]) in patients who received clopidogrel versus aspirin. The risk of bleeding was also lower for clopidogrel versus aspirin (0.57 [0.45, 0.74]). There was no difference in the rate of all-cause mortality between the two groups.

Conclusions

The analysis showed lower risks of major adverse cardiovascular or cerebrovascular events, recurrent stroke, and bleeding events for clopidogrel monotherapy compared to aspirin. These findings support clinical benefit for single antiplatelet therapy with clopidogrel over aspirin for secondary prevention in patients with recent ischemic stroke.

Comparison Between Aspirin and Clopidogrel in Secondary Stroke Prevention Based on Real-World Data

Background

Clopidogrel was thought to be superior to aspirin for secondary prevention of vascular diseases in clinical trials. In this study we assessed the safety and efficacy of clopidogrel versus aspirin in real‐world practice by using the Taiwan Stroke Registry.

Methods and Results

Patients with ischemic stroke (2006–2016) on aspirin or clopidogrel for secondary stroke prevention were identified in the Taiwan Stroke Registry. Stroke recurrence and mortality rates in patients receiving aspirin (N=34 679) were compared with those receiving clopidogrel (N=7611) during a 12‐month follow‐up period. Propensity score matching and conditional Cox proportional hazards regression model were applied to control confounding factors with 6443 patients in each group. After propensity score matching, stroke recurrence rates were comparable between groups, with 223 patients in the aspirin (3.46%) and 244 in the clopidogrel group (3.79%) (hazard ratio=1.13, 95% confidence interval=0.89–1.43, P=0.311). However, the mortality rate was significantly higher in the clopidogrel group (362 patients, 5.62%) than in the aspirin group (302 patients, 4.69%) (hazard ratio=1.30, 95% confidence interval=1.07–1.58, P=0.008). Results were consistent before and after propensity score matching.

Conclusions

Clopidogrel was as effective as aspirin for prevention of recurrent stroke in real‐world practice. However, the mortality rate was significantly higher in the clopidogrel than in the aspirin group.

Aspirin better than clopidogrel on major adverse cardiovascular events reduction after ischemic stroke: A retrospective nationwide cohort study

Background

Several clinical trials reported that clopidogrel was superior to aspirin in secondary stroke prevention by reducing the risk of major adverse cardiovascular events (MACE). We aimed to compare the efficacy of clopidogrel with aspirin in reducing one-year risk of MACE based on real-world evidence from Taiwan Health Insurance Database.

Methods

We identified ischemic stroke patients between 2000 and 2012 who took aspirin or clopidogrel within 7 days of stroke onset for 1-year follow-up. The primary outcome was one-year MACE including recurrent stroke, acute myocardial infarction, and death. Propensity score matching and conditional Cox proportional hazards regression were conducted to control the confounding factors.

Results

From 9,089 ischemic stroke patients, we found 654 patients on aspirin and 465 patients on clopidogrel who met the selective inclusion criteria. After propensity score matching, 379 patients were selected from each group. The clopidogrel group had a 1.78-fold MACE risk compared with the aspirin group at one-year follow-up (95% CI = 1.41–2.26, p<0.01). The MACE-free rate in the aspirin group was 15.74% higher than in the clopidogrel group at one-year follow-up. Sub-analysis of the three components of MACE showed that clopidogrel conferred higher risk of recurrent stroke (OR 1.43, 95% CI = 1.06–1.92, p 0.02) and acute myocardial infarction (OR 3.72, 95% CI = 1.04–13.3, p 0.04), but no different risk of death than that of aspirin.

Conclusions

Among first-ever ischemic stroke patients, secondary stroke prevention using clopidogrel was associated with higher rates of MACE than aspirin. Aspirin might have better efficacy in secondary stroke prevention and was associated with lower risk of MACE. The real-world evidence raises the need to re-assess the current therapeutic options in secondary stroke prevention applying aspirin vs. clopidogrel.