Platelets
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Ticagrelor is a novel direct-acting P2Y12 receptor antagonist used for preventing atherothrombotic events in patients with acute coronary syndromes (ACS). The current recommended dose is 90 mg bid, but a low dose of ticagrelor has not been previously studied in Chinese ACS patients. Therefore, we performed this study to observe the different effects of half- and standard-dose ticagrelor on platelet aggregation in Chinese patients with NSTE-ACS. ⋯ There were no significant differences in PRU and IPA between the two ticagrelor groups (P = 0.3085 and 0.4028, respectively). HPR rates were significantly lower in the two ticagrelor groups (0% for both) than those in the clopidogrel group (35%). In conclusion, half-dose ticagrelor had a similar inhibitory effect on platelet aggregation as standard-dose ticagrelor in Chinese patients with NSTE-ACS, which was significantly stronger than that of clopidogrel.
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Cangrelor is a rapid-acting, direct-binding, and reversible P2Y12 antagonist which has been studied for use during percutaneous coronary intervention (PCI) in patients with or without pretreatment with an oral P2Y12 antagonist. As cangrelor is administered intravenously, it is necessary to switch to an oral P2Y12 antagonist following PCI, such as the thienopyridines clopidogrel, and prasugrel or the non-pyridine ticagrelor. Previous studies have suggested a negative pharmacodynamic interaction between cangrelor and thienopyridines. ⋯ The thienopyridine AMs had limited ability to compete with cangrelor for binding to P2Y12 (% P2Y12 receptor blockade after co-incubation with cangrelor 1000 nmol/L: 11.7% for clopidogrel AM 3 µmol/L; 34.1% for prasugrel AM 3 µmol/L). In conclusion, in vitro cangrelor strongly inhibits the binding of clopidogrel and prasugrel AMs to the P2Y12 receptor, consistent with the previous observation of a negative pharmacodynamic interaction. Care may need to be taken to not overlap exposure to thienopyridine AMs and cangrelor in order to reduce the risk of thrombotic complications following PCI.
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Platelet function tests are suggested to assess platelet reactivity before cardiac and major non-cardiac surgery. Different point-of-care platelet function tests are available. Among these, electric impedance platelet aggregometry (EIPA) (Multiplate®, MP) is one of the most widely used techniques. ⋯ Platelet function assessment with RP greatly differs from the equivalent MP measure, and no correction value can be applied due to the low level of precision. This applies both to ADPtest and TRAPtest. The MP ADPtest is more reliable for platelet reactivity after discontinuation of P2Y12 receptor inhibitors.
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Platelets of patients with sickle cell disease (SCD) show evidence of mild activation in the non-crisis steady state and greater activation during vaso-occlusive crises (VOC). Prasugrel, a potent inhibitor of ADP-mediated platelet activation and aggregation, may be useful in attenuating VOC. We compared platelet responses to ADP stimulation in patients with SCD and healthy subjects before and after treatment with prasugrel. ⋯ Furthermore, prasugrel decreases ex vivo ADP-stimulated platelet aggregation with monocytes and neutrophils as measured by the monocyte-platelet and neutrophil-platelet aggregate MFI. This implies that in the presence of prasugrel, fewer platelets adhere to monocytes and neutrophils, which may result in reducing cell-platelet aggregate size. Therefore, reduced platelet reactivity and decreased size of leukocyte-platelet aggregates suggest additional mechanisms by which prasugrel may provide benefit to patients with SCD and support further investigation of possible therapeutic benefits of prasugrel in this population.
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Primary immune thrombocytopenia (ITP) is an autoimmune disease characterized by chronically low peripheral blood platelet counts. Eltrombopag is an oral, non-peptide, thrombopoietin-receptor agonist that increases platelet production. This report examines peri-procedural platelet counts and bleeding complications among chronic ITP patients requiring dental procedures while participating in clinical studies with eltrombopag. ⋯ Among patients with chronic ITP who required a dental procedure during clinical studies of eltrombopag, supplemental ITP treatment was required for both patients who received placebo but was not required for most patients who received eltrombopag. No bleeding complications were reported. These data imply that patients with chronic ITP who receive eltrombopag and experience increases in platelet counts fulfill current pre-procedural platelet count recommendations to undergo invasive dental procedures, and may have a lower risk of bleeding complications and a reduced need for supplemental ITP treatment.