Interaction between clopidogrel and proton-pump inhibitors and management strategies in patients with cardiovascular diseases

Dual antiplatelet therapy (DAPT) with clopidogrel and aspirin has been successful in reducing ischemic events in a wide range of patients with cardiovascular diseases. However, the anti-ischemic effects of DAPT may also be associated with gastrointestinal (GI) complications including ulceration and bleeding particularly in ‘high risk’ and elderly patients. Current guidelines recommend the use of proton-pump inhibitors (PPIs) to reduce the risk of GI bleeding in patients treated with DAPT. However, pharmacodynamic studies suggest an effect of PPIs on clopidogrel metabolism with a resultant reduction in platelet inhibitory effects. Similarly, several observational studies have demonstrated reduced clopidogrel benefit in patients who coadministered PPIs. Although recent US Food and Drug Administration and European Medicines Agency statements discourage PPI (particularly omeprazole) and clopidogrel coadministration, the 2009 AHA/ACC/SCAI PCI guidelines do not support a change in current practice in the absence of adequately powered prospective randomized clinical trial data. The data regarding pharmacologic and clinical interactions between PPI and clopidogrel therapies are herein examined and treatment strategies are provided

High platelet reactivity in patients with acute coronary syndromes undergoing percutaneous coronary intervention: Randomised controlled trial comparing prasugrel and clopidogrel

Background: Prasugrel is more effective than clopidogrel in reducing platelet aggregation in acute coronary syndromes. Data available on prasugrel reloading in clopidogrel treated patients with high residual platelet reactivity (HRPR) i.e. poor responders, is limited. Objectives: To determine the effects of prasugrel loading on platelet function in patients on clopidogrel and high platelet reactivity undergoing percutaneous coronary intervention for acute coronary syndrome (ACS). Patients: Patients with ACS on clopidogrel who were scheduled for PCI found to have a platelet reactivity ≥40 AUC with the Multiplate Analyzer, i.e. “poor responders” were randomised to prasugrel (60 mg loading and 10 mg maintenance dose) or clopidogrel (600 mg reloading and 150 mg maintenance dose). The primary outcome measure was proportion of patients with platelet reactivity <40 AUC 4 hours after loading with study medication, and also at one hour (secondary outcome). 44 patients were enrolled and the study was terminated early as clopidogrel use decreased sharply due to introduction of newer P2Y12 inhibitors. Results: At 4 hours after study medication 100% of patients treated with prasugrel compared to 91% of those treated with clopidogrel had platelet reactivity <40 AUC (p = 0.49), while at 1 hour the proportions were 95% and 64% respectively (p = 0.02). Mean platelet reactivity at 4 and 1 hours after study medication in prasugrel and clopidogrel groups respectively were 12 versus 22 (p = 0.005) and 19 versus 34 (p = 0.01) respectively. Conclusions: Routine platelet function testing identifies patients with high residual platelet reactivity (“poor responders”) on clopidogrel. A strategy of prasugrel rather than clopidogrel reloading results in earlier and more sustained suppression of platelet reactivity. Future trials need to identify if this translates into clinical benefit

International Expert Consensus on Switching Platelet P2Y(12) Receptor-Inhibiting Therapies

Dual antiplatelet therapy with aspirin and a P2Y(12) inhibitor is the treatment of choice for the prevention of atherothrombotic events in patients with acute coronary syndromes and for those undergoing percutaneous coronary interventions. The availability of different oral P2Y(12) inhibitors (clopidogrel, prasugrel, ticagrelor) has enabled physicians to contemplate switching among therapies because of specific clinical scenarios. The recent introduction of an intravenous P2Y(12) inhibitor (cangrelor) further adds to the multitude of modalities and settings in which switching therapies may occur. In clinical practice, it is not uncommon to switch P2Y(12) inhibitor, and switching may be attributed to a variety of factors. However, concerns about the safety of switching between these agents have emerged. Practice guidelines have not fully elaborated on how to switch therapies, leaving clinicians with limited guidance on when and how to switch therapies when needed. This prompted the development of this expert consensus document by key leaders from North America and Europe with expertise in basic, translational, and clinical sciences in the field of antiplatelet therapy. This expert consensus provides an overview of the pharmacology of P2Y(12) inhibitors, different modalities and definitions of switching, and available literature and recommendations for switching between P2Y(12) inhibitors

'Aspirin resistance' or treatment non-compliance: Which is to blame for cardiovascular complications?

Aspirin is one of the 'cornerstone' drugs in our current management of cardiovascular disorders. However, despite the prescription of aspirin recurrent vascular events still occur in 10–20% of patients. These, data together with the observations of diminished antiaggregatory response to aspirin in some subjects have provided the basis of the current debate on the existence of so-called "aspirin resistance". Unfortunately, many of the tests employed to define 'aspirin resistance' lack sufficient sensitivity, specificity, and reproducibility. The prevalence of 'aspirin resistance' as defined by each test varies widely, and furthermore, the value of a single point estimate measure of aspirin resistance is questionable. The rate of 'aspirin resistance' is law if patients observed to ingest aspirin, with large proportion of patients to be pseudo-'aspirin resistant', due to non-compliance. What are the implications for clinical practice? Possible non-adherence to aspirin prescription should also be carefully considered before changing to higher aspirin doses, other antiplatelet drugs (e.g. clopidogrel) or even combination antiplatelet drug therapy. Given the multifactorial nature of atherothrombotic disease, it is not surprising that only about 25% of all cardiovascular complications can usually be prevented by any single medication. We would advocate against routine testing of platelet sensitivity to aspirin (as an attempt to look for 'aspirin resistance') but rather, to highlight the importance of clinicians and public attention to the problem of treatment non-compliance

Platelet inhibition with ticagrelor 60 mg versus 90 mg twice daily in the PEGASUS-TIMI 54 trial

Background The PEGASUS-TIMI 54 (Prevention of Cardiovascular Events in Patients with Prior Heart Attack Using Ticagrelor Compared to Placebo on a Background of Aspirin–Thrombolysis In Myocardial Infarction 54) trial studied 2 doses of ticagrelor, 90 mg twice a day (bid) and 60 mg bid, for long-term prevention of ischemic events in patients with prior myocardial infarction. Both doses similarly reduced the rate of ischemic events versus placebo. The pharmacokinetics and pharmacodynamics of ticagrelor 60 mg bid have not been studied. Objectives In this study, the authors sought to study the pharmacokinetics and pharmacodynamics for ticagrelor 60 mg compared with 90 mg bid. Methods A total of 180 patients who received >4 weeks of study medication had blood sampling in the morning pre-maintenance dose and again 2 h post-dose. All patients received aspirin. Plasma levels of ticagrelor and its active metabolite AR-C124910XX were determined. P2Y12 inhibition was assessed by the VerifyNow P2Y12 assay (Accumetrics, Inc., San Diego, California) (P2Y12 reaction units [PRU]), light transmittance aggregometry (adenosine diphosphate 5 and 20 μmol/l and arachidonic acid), and vasodilator-stimulated phosphoprotein phosphorylation assays. VerifyNow Aspirin assays and serum thromboxane B2 measurements were performed. Results Mean pre- and post-dose plasma levels of ticagrelor were 35% and 38% lower, respectively, with 60 mg versus 90 mg. Both doses achieved high levels of platelet inhibition pre- and post-dose, with numerically slightly more variability with 60 mg: mean (SD) pre-dose PRU values were 59 ± 63 and 47 ± 43 for ticagrelor 60 and 90 mg, respectively (p = 0.34). High platelet reactivity, determined as PRU >208, was rare with the 60-mg pre-dose and was absent post-dose. Platelet reactivity pre- and post-dose, as measured by light transmittance aggregometry or vasodilator-stimulated phosphoprotein assays, was numerically but not significantly lower with 90 mg than with 60 mg. Aspirin response was not affected by either dose. Conclusions Ticagrelor 60 mg bid achieved high levels of peak and trough platelet inhibition in nearly all patients, similar to that with 90 mg bid, helping to explain the efficacy of the lower ticagrelor dose in PEGASUS-TIMI 54

Development of selective agonists and antagonists of P2Y receptors

Although elucidation of the medicinal chemistry of agonists and antagonists of the P2Y receptors has lagged behind that of many other members of group A G protein-coupled receptors, detailed qualitative and quantitative structure–activity relationships (SARs) were recently constructed for several of the subtypes. Agonists selective for P2Y1, P2Y2, and P2Y6 receptors and nucleotide antagonists selective for P2Y1 and P2Y12 receptors are now known. Selective nonnucleotide antagonists were reported for P2Y1, P2Y2, P2Y6, P2Y11, P2Y12, and P2Y13 receptors. At the P2Y1 and P2Y12 receptors, nucleotide agonists (5′-diphosphate derivatives) were converted into antagonists of nanomolar affinity by altering the phosphate moieties, with a focus particularly on the ribose conformation and substitution pattern. Nucleotide analogues with conformationally constrained ribose-like rings were introduced as selective receptor probes for P2Y1 and P2Y6 receptors. Screening chemically diverse compound libraries has begun to yield new lead compounds for the development of P2Y receptor antagonists, such as competitive P2Y12 receptor antagonists with antithrombotic activity. Selective agonists for the P2Y4, P2Y11, and P2Y13 receptors and selective antagonists for P2Y4 and P2Y14 receptors have not yet been identified. The P2Y14 receptor appears to be the most restrictive of the class with respect to modification of the nucleobase, ribose, and phosphate moieties. The continuing process of ligand design for the P2Y receptors will aid in the identification of new clinical targets

Prolonged antithrombotic therapy in patients after acute coronary syndrome: A critical appraisal of current European Society of Cardiology guidelines

The increased risk of non-cardiovascular death in patients receiving clopidogrel or prasugrel in comparison with the placebo group in the Dual Antiplatelet Therapy (DAPT) trial in contrast to the decreased risk of cardiovascular death and all-cause death seen in patients treated with low-dose ticagrelor in the EU label population of the PEGASUS-TIMI 54 trial, resulted in inclusion in the 2020 ESC NSTE-ACS guidelines the recommendation for use of clopidogrel or prasugrel only if the patient is not eligible for treatment with ticagrelor.The prevalence of the primary outcome composed of cardiovascular death, stroke, or myocardial infarction was lower in the low-dose rivaroxaban and acetylsalicylic acid (ASA) group than in the ASA-alone group in the COMPASS trial. Moreover, all-cause mortality and cardiovascular mortality rates were lower in the rivaroxaban-plus-ASA group.Comparison of the PEGASUS-TIMI 54 and COMPASS trial patient characteristics clearly shows that each of these treatment strategies should be addressed at different groups of patients. A greater benefit in post-acute coronary syndrome (ACS) patients with a high risk of ischemic events and without high bleeding risk may be expected with ASA and ticagrelor 60 mg b.i.d. when the therapy is continued without interruption or with short interruption only after ACS. On the other hand, ASA and rivaroxaban 2.5 mg b.i.d. seems to be a better option when indications for dual antithrombotic therapy (DATT) appear after a longer time from ACS (more than 2 years) and/or from cessation of DAPT (more than 1 year) and in patients with multiple vascular bed atherosclerosis. Thus, both options of DATTs complement each other rather than compete, as can be presumed from the recommendations. However, a direct comparison between these strategies should be tested in future clinical trials

Prolonged antithrombotic therapy in patients after acute coronary syndrome: A critical appraisal of current European Society of Cardiology guidelines

The increased risk of non-cardiovascular death in patients receiving clopidogrel or prasugrel in comparison with the placebo group in the dual antiplatelet therapy (DAPT) trial in contrast to the decreased risk of cardiovascular death and all-cause death seen in patients treated with low-dose ticagrelor in the EU label population of the PEGASUS-TIMI 54 trial, resulted in inclusion in the 2020 ESC NSTE-ACS guidelines the recommendation for use of clopidogrel or prasugrel only if the patient is not eligible for treatment with ticagrelor. The prevalence of the primary outcome composed of cardiovascular death, stroke, or myocardial infarction was lower in the low-dose rivaroxaban and acetylsalicylic acid (ASA) group than in the ASA-alone group in the COMPASS trial. Moreover, all-cause mortality and cardiovascular mortality rates were lower in the rivaroxaban-plus-ASA group. Comparison of the PEGASUS-TIMI 54 and COMPASS trial patient characteristics clearly shows that each of these treatment strategies should be addressed at different groups of patients. A greater benefit in postacute coronary syndrome (ACS) patients with a high risk of ischemic events and without high bleeding risk may be expected with ASA and ticagrelor 60 mg b.i.d. when the therapy is continued without interruption or with short interruption only after ACS. On the other hand, ASA and rivaroxaban 2.5 mg b.i.d. seems to be a better option when indications for dual antithrombotic treatment (DATT) appear after a longer time from ACS (more than two years) and/or from cessation of DAPT (more than one year) and in patients with multiple vascular bed atherosclerosis. Thus, both options of DATTs complement each other rather than compete, as can be presumed from the recommendations. However, a direct comparison between these strategies should be tested in future clinical trials

Platelet reactivity influences clot structure as assessed by fractal analysis of viscoelastic properties

<p>Despite the interwoven nature of platelet activation and the coagulation system in thrombosis, few studies relate both analysis of protein and cellular parts of coagulation in the same population. In the present study, we use matched ex vivo samples to determine the influences of standard antiplatelet therapies on platelet function and use advanced rheological analyses to assess clot formation. Healthy volunteers were recruited following fully informed consent then treated for 7 days with single antiplatelet therapy of aspirin (75 mg) or prasugrel (10 mg) or with dual antiplatelet therapy (DAPT) using aspirin (75 mg) plus prasugrel (10 mg) or aspirin (75 mg) plus ticagrelor (90 mg). Blood samples were taken at day 0 before treatment and at day 7 following treatment. We found that aspirin plus prasugrel or aspirin plus ticagrelor inhibited platelet responses to multiple agonists and reduced P-selectin expression. Significant platelet inhibition was coupled with a reduction in fractal dimension corresponding to reductions in mean relative mass both for aspirin plus prasugrel (−35 ± 16% change, p = 0.04) and for aspirin plus ticagrelor (−45 ± 14% change, p = 0.04). Aspirin alone had no effect upon measures of clot structure, whereas prasugrel reduced fractal dimension and mean relative mass. These data demonstrate that platelets are important determinants of clot structure as assessed by fractal dimension (d_<i>f</i>) and that effective platelet inhibition is associated with a weaker, more permeable fibrin network. This indicates a strong association between the therapeutic benefits of antiplatelet therapies and their abilities to reduce thrombus density that may be useful in individual patients to determine the functional relationship between platelet reactivity, eventual clot quality, and clinical outcome. d_<i>f</i> could represent a novel risk stratification biomarker useful in individualizing antiplatelet therapies.</p