Why does ticagrelor induce dyspnea?
Marco Cattaneo, MD, Medicina 3, Dipartimento di Scienze della Salute, Università degli Studi di Milano, Via A. di Rudinì 8, 20142 Milano, Italy, Tel.: +39 02 503 23095, Fax: +39 02 503 23089, E-mail: . Thrombosis and Haemostasis
(Impact Factor: 4.98).
10/2012; 108(6). DOI: 10.1160/TH12-08-0547
In studies that compared the reversible P2Y12 inhibitor ticagrelor with the irreversible inhibitor clopidogrel, dyspnea was observed more frequently among ticagrelor-treated patients than among clopidogrel-treated patients. Because dyspnea was not associated with acidosis, pulmonary or cardiac dysfunction, alterations in the mechanisms and pathways of the sensation of dyspnea may be involved in its pathogenesis. It has been hypothesised that the sensation of dyspnea in ticagrelor-treated patients is triggered by adenosine, because ticagrelor inhibits its clearance, thereby increasing its concentration in the circulation. However, dipyridamole, a much stronger inhibitor of adenosine clearance than ticagrelor, usually does not cause dyspnea. We hypothesise that inhibition of P2Y12 on sensory neurons increases the sensation of dyspnea, particularly when reversible inhibitors are used. We base our hypothesis on the following considerations: 1) cangrelor and elinogrel, which, like ticagrelor, are reversible P2Y12 inhibitors, also increase the incidence of dyspnea; 2) it is biologically plausible that inhibition of P2Y12 on sensory neurons increases the sensation of dyspnea; 3) inhibition of P2Y12 on platelets (which do not have a nucleus) by clopidogrel is permanent, despite the once daily administration and the short plasma half-life of the inhibitor; 4) in contrast, inhibition of P2Y12 on neurons by clopidogrel may be temporary and transient, because neurons have a nucleus and can therefore rapidly replace the inhibited receptors with newly synthetised ones; 5) inhibition of P2Y12 on neurons by reversible inhibitors is permanent, because the plasma drug concentration is maintained high by repeated dosing, in order to ensure permanent inhibition of platelet P2Y12.
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ABSTRACT: Platelets play a key role in the pathogenesis of atherothrombosis, involved in both the development and progression of atherosclerotic heart disease, and the attendant acute thrombotic complications. Antiplatelet therapy constitutes a mainstay therapy for patients with acute coronary syndromes and generally high-risk patients with atherothrombosis. Until recently, dual antiplatelet therapy (DAPT) for the treatment and prevention of the complications of atherothrombotic disease was traditionally limited to aspirin plus clopidogrel. However, a most important pertaining issue emerged, that of the occurrence of drug-resistance or tolerance observed in some patients for both these antithrombotic agents, which limited the efficacy and applicability of this combined therapy. The availability of the newer thienopyridine, prasugrel, and the cyclopentyl-triazolopyrimidine, ticagrelor, represents an important addition to the physician's armamentarium. Dual antiplatelet therapy (DAPT) with aspirin and clopidogrel or one of the newer agents interferes with platelet activation in complementary, but separate pathways. Aspirin irreversibly inhibits cyclooxygenase, thus preventing the production of thromboxane A2, which is a prothrombotic and vasoconstrictive substance. Thienopyridines (clopidogrel/prasugrel) irreversibly and ticagrelor reversibly prevent and inhibit platelet activation by blocking one of the three known adenosine 5'-diphosphate (ADP) receptors (the P2Y12 receptor) on the platelet surface, thus interfering with platelet activation, degranulation and aggregation. Each of these antiplatelet agents has a protective effect against adverse vascular events; classical DAPT with aspirin and clopidogrel has an even stronger antiplatelet effect compared with either agent alone, however DAPT combining aspirin with one of the newer more potent agents translates into superior antithrombotic protection in atherothrobotic vascular disease, albeit at an increased, though not inordinately, risk for bleeding complications. A number of randomized clinical trials have demonstrated and confirmed the incremental benefit and efficacy of DAPT with use of either classical or newer agents, above and beyond that of each antiplatelet agent alone. Data have also been obtained from studies where indications for the use of DAPT continue to expand into other patient groups, rendering and maintaining DAPT a sweeping combination in Cardiology. This article is a comprehensive review of all these data and the landmark trials on the two classical and also the newer antiplatelet agents, the issues involved and the current recommendations for their use in patients with atherosclerotic heart disease and other cardiovascular disorders and procedures.
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ABSTRACT: The considerable progress in P2Y12-platelet blockers has important perioperative implications due to a family of novel agents beyond clopidogrel. Although prasugrel is more potent than clopidogrel due to more efficient hepatic metabolism, it is limited clinically by its irreversibility and bleeding risks. Ticagrelor, as the first approved direct and reversible oral P2Y12 blocker, still is limited clinically by its novel side-effect profile. Intravenous reversible P2Y12 blockade is possible now with both cangrelor and elinogrel, although both agents are still in clinical development. Furthermore, elinogrel offers the possibility of both oral and parenteral P2Y12 blockade with a single agent. Future trials likely will continue to evaluate and compare the safety and efficacy of these agents in multiple clinical settings, including the perioperative period.
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