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Clinical importance of aspirin and clopidogrel resistance  [cached]
Gergely Feher,Andrea Feher,Gabriella Pusch,Katalin Koltai
World Journal of Cardiology , 2010,
Abstract: Aspirin and clopidogrel are important components of medical therapy for patients with acute coronary syndromes, for those who received coronary artery stents and in the secondary prevention of ischaemic stroke. Despite their use, a significant number of patients experience recurrent adverse ischaemic events. Interindividual variability of platelet aggregation in response to these antiplatelet agents may be an explanation for some of these recurrent events, and small trials have linked “aspirin and/or clopidogrel resistance”, as measured by platelet function tests, to adverse events. We systematically reviewed all available evidence on the prevalence of aspirin/clopidogrel resistance, their possible risk factors and their association with clinical outcomes. We also identified articles showing possible treatments. After analyzing the data on different laboratory methods, we found that aspirin/clopidogrel resistance seems to be associated with poor clinical outcomes and there is currently no standardized or widely accepted definition of clopidogrel resistance. Therefore, we conclude that specific treatment recommendations are not established for patients who exhibit high platelet reactivity during aspirin/clopidogrel therapy or who have poor platelet inhibition by clopidogrel.
Aspirin and clopidogrel resistance: methodological challenges and opportunities  [cached]
Armen Yuri Gasparyan
Vascular Health and Risk Management , 2010,
Abstract: Armen Yuri GasparyanClinical Research Unit, Russell’s Hall Hospital, Dudley Group of Hospitals NHS Foundation Trust, West Midlands, UKAbstract: Antiplatelet drug resistance is one of the urgent issues in current cardiovascular medicine. Many platelet function tests have been used to define responsiveness of patients with cardiovascular disease to aspirin and clopidogrel. In most studies, cut-off values of platelet function tests for defining responsiveness to antiplatelets were chosen arbitrarily. Different tests provided wide-ranging figures of the prevalence of aspirin and clopidogrel resistance, suggesting poor correlation between currently available platelet function tests. Measurement of platelet size seems to be a promising approach for monitoring antiplatelet drug therapy. This commentary highlights some limitations of studies on aspirin and clopidogrel resistance in patients undergoing coronary interventions.Keywords: aspirin, clopidogrel, resistance, cardiovascular disease, platelet function tests
Effects of Combined Aspirin and Clopidogrel Therapy on Cardiovascular Outcomes: A Systematic Review and Meta-Analysis  [PDF]
Yu-Hao Zhou, Xin Wei, Jian Lu, Xiao-Fei Ye, Mei-Jing Wu, Jin-Fang Xu, Ying-Yi Qin, Jia He
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031642
Abstract: Background Aspirin and clopidogrel monotherapies are effective treatments for preventing vascular disease. However, new evidence has emerged regarding the use of combined aspirin and clopidogrel therapy to prevent cardiovascular events. We therefore performed a comprehensive systematic review and meta-analysis to evaluate the benefits and harms of combined aspirin and clopidogrel therapy on major cardiovascular outcomes. Methodology/Principal Findings We systematically searched Medline, Embase, the Cochrane Central Register of Controlled Trials, reference lists of articles, and proceedings of major meetings to identify studies to fit our analysis. Eligible studies were randomized controlled trials assessing the effect of combined aspirin and clopidogrel therapy compared with aspirin or clopidogrel monotherapy. We identified 7 trials providing data with a total of 48248 patients. These studies reported 5134 major cardiovascular events, 1626 myocardial infarctions, 1927 strokes, and 1147 major bleeding events. Overall, the addition of aspirin to clopidogrel therapy as compared to single drug therapy resulted in a 9% RR reduction (95%CI, 2 to 17) in major cardiovascular events, 14% RR reduction (95%CI, 3 to 24) in myocardial infarction, 16% RR reduction (95%CI, 1 to 28) in stroke, and 62% RR increase (95%CI, 26 to 108) in major bleeding events. We also present the data as ARR to explore net value as the reduction in cardiovascular events. Overall, we observed that combined therapy yielded 1.06% decrease (95%CI, 0.23% to 1.99%) in major cardiovascular events and 1.23% increase (95%CI, 0.52% to 2.14%) in major bleeding events. Conclusion/Significance Although the addition of aspirin to clopidogrel resulted in small relative reductions in major cardiovascular events, myocardial infarction, and stroke, it also resulted in a relative increase in major bleeding events. In absolute terms the benefits of combined therapy, a 1.06% reduction in major cardiovascular events, does not outweigh the harms, a 1.23% increase in major bleeding events.
Comparison of a New P2Y12 Receptor Specific Platelet Aggregation Test with Other Laboratory Methods in Stroke Patients on Clopidogrel Monotherapy  [PDF]
Zsuzsa Bagoly, Ferenc Sarkady, Tünde Magyar, János Kappelmayer, Endre Pongrácz, László Csiba, László Muszbek
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0069417
Abstract: Background Clinical studies suggest that 10-50% of patients are resistant to clopidogrel therapy. ADP induced platelet aggregation, a widely used test to monitor clopidogrel therapy, is affected by aspirin and is not specific for the P2Y12 receptor inhibited by clopidogrel. Objectives To develop a P2Y12-specific platelet aggregation test and to compare it with other methods used for monitoring clopidogrel therapy. Patients/Methods Study population included 111 patients with the history of ischemic stroke being on clopidogrel monotherapy and 140 controls. The effect of clopidogrel was tested by a newly developed ADP(PGE1) aggregation test in which prostaglandin E1 treated platelets are used. Results of conventional ADP induced platelet aggregation, VerifyNow P2Y12 assay and ADP(PGE1) aggregation were compared to those obtained by flow cytometric analysis of vasodilator stimulated phosphoprotein (VASP) phosphorylation. Reference intervals for all assays were determined according to the guidelines of Clinical Laboratory Standards Institute. Results The P2Y12-specificity of ADP(PGE1) test was proven by comparing it with ADP aggregation in the presence of P2Y1 antagonist, adenosine 3’, 5’-diphosphate. The method was not influenced by aspirin treatment. Approximately 50% of patients were clopidogrel resistant by conventional ADP aggregation and VerifyNow tests. The ADP(PGE1) method and the VASP phosphorylation assay identified 25.9% and 11.7% of patients as non-responders, respectively. ADP(PGE1) aggregation showed good correlation with VASP phosphorylation and had high diagnostic efficiency. Conclusion The new ADP(PGE1) method is a reliable test for monitoring P2Y12 receptor inhibition by platelet aggregation. As a subset of patients are non-responders, monitoring clopidogrel therapy by adequate methods is essential.
Aspirin and clopidogrel resistance: methodological challenges and opportunities
Armen Yuri Gasparyan
Vascular Health and Risk Management , 2010, DOI: http://dx.doi.org/10.2147/VHRM.S9087
Abstract: spirin and clopidogrel resistance: methodological challenges and opportunities Commentary (5935) Total Article Views Authors: Armen Yuri Gasparyan Published Date March 2010 Volume 2010:6 Pages 109 - 112 DOI: http://dx.doi.org/10.2147/VHRM.S9087 Armen Yuri Gasparyan Clinical Research Unit, Russell’s Hall Hospital, Dudley Group of Hospitals NHS Foundation Trust, West Midlands, UK Abstract: Antiplatelet drug resistance is one of the urgent issues in current cardiovascular medicine. Many platelet function tests have been used to define responsiveness of patients with cardiovascular disease to aspirin and clopidogrel. In most studies, cut-off values of platelet function tests for defining responsiveness to antiplatelets were chosen arbitrarily. Different tests provided wide-ranging figures of the prevalence of aspirin and clopidogrel resistance, suggesting poor correlation between currently available platelet function tests. Measurement of platelet size seems to be a promising approach for monitoring antiplatelet drug therapy. This commentary highlights some limitations of studies on aspirin and clopidogrel resistance in patients undergoing coronary interventions.
Is clopidogrel superior to aspirin in secondary prevention of vascular disease?
Ale Algra, Jan van Gijn
Trials , 2000, DOI: 10.1186/cvm-1-3-143
Abstract: A nice bottle of Graves arrived at our offices in early August 2000. The Dutch branch of Sanofi-Synthelabo sent this wine to collaborators of the Clopidogrel versus Aspirin in Patients at Risk of Ischaemic Events (CAPRIE) trial [1] to celebrate the regulation of reimbursement for clopidogrel in the Netherlands on 26 July. The official indication for this novel antiplatelet drug reads: 'secondary prevention in patients with atherosclerotic disease and proven aspirin sensitivity'. Sanofi-Synthelabo appealed against the limitation to patients intolerant to aspirin, but lost the lawsuit [2].What is the background of this legal quarrel? The cornerstone is clinical evidence from the CAPRIE trial, a ran-domised, blinded, international study [1]. Clopidogrel (75 mg daily) and aspirin (325 mg daily) were compared in the prevention of the composite outcome event 'vascular death, nonfatal stroke or nonfatal myocardial infarction'. Clopidogrel reduced the annual risk of such a vascular event from 5.83 to 5.32% in comparison with aspirin, corresponding to a relative risk reduction (RRR) of 8.7%. The 95% confidence interval just kept clear of the neutral value and ranged from 0.3 to 16.5%. The design of the study was based on the paradigm prevalent in the early 1990s: all clinical presentations of atherosclerotic disease should be regarded as different manifestations of a single disorder of the arterial vascular tree. The data of the CAPRIE trial do not necessarily support this paradigm, because the RRR values of the three diagnostic strata (each with over 6000 patients) differed considerably: -3.7% for myocardial infarction, +7.3% for ischaemic stroke, and 23.8% for peripheral arterial disease (P = 0.042). A similar difference between different categories of atherosclerotic disease had been observed by the AntiPlatelet Trialists' Collaboration [3]. The RRR values achieved by aspirin (compared with placebo) ranged from 18% for cerebral ischaemia to 35% for unstable angina.Clopido
RP-HPLC analysis of aspirin and clopidogrel bisulphate in combination  [cached]
Anandakumar K,Ayyappan T,Raghu Raman V,Vetrichelvan T
Indian Journal of Pharmaceutical Sciences , 2007,
Abstract: A reverse phase high performance liquid chromatography method was developed for the simultaneous estimation of aspirin and clopidogrel bisulphate in formulation. The separation was achieved by octadecyl column (C 18 ) and acetonitrile:methanol:20 mM phosphate buffer at pH 3 (50:7:43 v/v) as eluent, at a flow rate of 1 ml/min. Detection was carried out at 240 nm. Quantitation was done by external standard calibration method. The retention time of aspirin and clopidogrel bisulphate was found to be 2.40 and 9.27 min, respectively. The method has been validated for linearity, accuracy and precision. Linearity for aspirin and clopidogrel bisulphate were in the range of 10-50 μg/ml for both the drugs. The mean recoveries obtained for aspirin and clopidogrel bisulphate were 100.86% and 100.20%, respectively. The developed method was found to be accurate, precise, selective and rapid for the simultaneous estimation of aspirin and clopidogrel bisulphate in capsules.
Simultaneous determination of clopidogrel and aspirin in pharmaceutical dosage forms  [cached]
Mishra P,Dolly Archana
Indian Journal of Pharmaceutical Sciences , 2006,
Abstract: Two simple spectrophotometric methods for the determination of aspirin and clopidogrel in pharmaceutical formulations have been developed. First method is based on the additivity of absorbances. Second method is based on the determination of graphical absorbance ratio at two selected wavelengths, one being the isoabsorptive point for the two drugs (225 nm) and the other being the absorption maximum of hydrolysed aspirin (235.7 nm). Beer Lambert′s law is obeyed for both the drugs in the concentration range 4-18 mg/ml. Both the methods were found to be simple, rapid, accurate and can be adopted in routine analysis of drugs in formulations. The accuracy and reproducibility of the proposed method was statistically validated by recovery studies.
Chemometric simultaneous estimation of clopidogrel bisulphate and aspirin from combined dosage form  [cached]
Rajput S,George R,Ruikar Deepti
Indian Journal of Pharmaceutical Sciences , 2008,
Abstract: Two chemometric methods, inverse least square and classical least square, were applied to simultaneous assay of clopidogrel bisulphate and aspirin in their combined dosage tablet formulation. Twelve mixed solutions were prepared for the chemometric calibration as training set and 10 mixed solutions were prepared as validation set. The absorbance data matrix was obtained by measuring the absorbance at 16 wavelength points, from 220 to 250 nm with the interval of 2 nm (Dl= 2 nm). The developed calibrations were successfully tested for laboratory mixtures as well as commercial tablet formulation for their clopidogrel bisulphate and aspirin concentration. Mean recoveries for clopidogrel bisulphate and aspirin were found to be in good agreement with the label claim.
High performance liquid chromatographic determination of aspirin and clopidogrel in tablets  [cached]
Gandhimathi M,Ravi T
Indian Journal of Pharmaceutical Sciences , 2007,
Abstract: A reverse phase high performance liquid chromatographic method to determine aspirin and clopidogrel in combined dosage form is proposed. The chromatographic resolution of aspirin and clopidogrel was obtained in a mobile phase consisting of 0.1% v/v triethylamine (pH 4.0):acetonitrile in the ratio 25:75% (v/v) in an isocratic elution. A detection wavelength of 225 nm and flow rate of 1 ml/min was used in the study. Nimesulide (20 μg/ml) was used as an internal standard. The system suitability procedures as precision, accuracy, LOD, LOQ, number of theoretical plates and tailing factor were studied.
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