Administration of a Loading Dose Has No Additive Effect on Platelet Aggregation During the Switch From Ongoing Clopidogrel Treatment to Ticagrelor in Patients With Acute Coronary Syndrome

Study Questions:

What is the effect of a ticagrelor loading dose on further platelet inhibition during the switch from clopidogrel to ticagrelor in patients with acute coronary syndrome (ACS) receiving ongoing antiplatelet treatment?


Fifty patients with ACS receiving aspirin and clopidogrel treatment were randomly assigned to a starting dose of ticagrelor (group 1, 90 mg; group 2, 180 mg). Platelet aggregation was measured using multiple electrode aggregometry and standard light transmission aggregometry (LTA) just before the switch and at 2, 6, 24, and 72 hours.


No relevant difference in platelet aggregation was observed between the two study arms at baseline (p = 0.256). Residual platelet aggregation was significantly reduced in both arms 2 hours after the first administration of ticagrelor (p < 0.001 for both), with no difference in aggregation between groups (multiple electrode aggregometry, 17.6 ± 7.2 vs. 18.1 ± 6 U; p = 0.281). Similar results were observed with LTA.


The authors concluded that switching from clopidogrel to ticagrelor without a reloading dose is feasible, and it does not hinder platelet aggregation inhibition in patients with ACS.


This study reports that the therapeutic switch from ongoing clopidogrel to ticagrelor treatment without the administration of a loading dose of ticagrelor seems to be safe and yields a similar level of residual platelet aggregation when compared with patients who received a ticagrelor loading dose. These findings would suggest that avoiding the loading dose of ticagrelor when switching the P2Y12 antiplatelet agent in clopidogrel-treated patients could be associated with a reduction in the incidence of bleeding complications, without affecting the efficacy profile of ticagrelor. If confirmed in future studies using clinical endpoints, this strategy of avoiding loading dose may improve patient safety while maintaining the significant efficacy of ticagrelor for reduction of cardiovascular events.

Clinical Topics: Acute Coronary Syndromes

Keywords: Acute Coronary Syndrome, Electrodes, Platelet Aggregation Inhibitors, Platelet Function Tests, Platelet Aggregation, Ticlopidine, Purinergic P2Y Receptor Antagonists

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