Randomized Assessment of Ticagrelor Versus Prasugrel Antiplatelet Effects in Patients With ST Elevation Myocardial Infarction
What is the relative pharmacological effect of ticagrelor and prasugrel in patients undergoing primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI)?
The authors randomized 55 patients undergoing primary PCI for STEMI to either ticagrelor 180 mg loading followed by 90 mg bid, or prasugrel 60 mg loading followed by 10 mg daily for 5 days. Platelet reactivity was assessed with the VerifyNow P2Y12 function assay and the Multiplate Analyzer at 0, 1, 2, 6, and 24 hours, and 5 days post-randomization.
There was no difference in the primary endpoint of platelet reactivity with VerifyNow assay at 1 hour between patients randomized to ticagrelor versus prasugrel (257.3 P2Y12 reaction unit [PRU] vs. 231.3 PRU; p = 0.2). Platelet reactivity did not differ with the two agents at 2, 6, and 24 hours, although it was lower with ticagrelor than prasugrel on day 5 (25.6 PRU, 95% confidence interval [CI], 12.3-38.9 vs. 50.3 PRU; 95% CI, 36.4-64.1; p = 0.01). At hour 2, high on-treatment platelet reactivity (defined as >208 PRU) was present in 46.2% of patients treated with ticagrelor and 34.6% of those treated with prasugrel.
The authors concluded that there is an initial delay in platelet inhibition with both ticagrelor and prasugrel, although both agents provide similar overall platelet inhibition.
Both prasugrel and ticagrelor provide more robust platelet inhibition compared with clopidogrel, but there are limited data comparing the two agents. This small trial suggests that both agents provide similar platelet inhibition in patients undergoing primary PCI for STEMI with somewhat delayed onset of action compared with what has been described in other clinical settings. It is not clear if this is something unique to STEMI patients or is specific to the study population. The small size of the study notwithstanding, the similar platelet inhibition in both arms suggests that both drugs may provide similar benefits in patients undergoing primary PCI.
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