For patients undergoing ad hoc PCI, the ticagrelor loading dose provides more effective platelet inhibition and lower high on-treatment platelet reactivity (HPR) than the clopidogrel loading dose, according to research published in the Journal of the American College of Cardiology.
Many patients who have a low risk of acute coronary syndrome (ACS) are not pre-treated with a P2Y12 receptor inhibitor, although many patients in this population undergo ad hoc PCI. Therefore, researchers compared the effects of ticagrelor with clopidogrel on platelet reactivity in the post-interventional period among troponin-negative ACS patients.
“In low-risk ACS patients undergoing ad hoc PCI and receiving the P2Y12 antagonist immediately after coronary angiography, platelet reactivity was decreased to a greater extent 2 h after ticagrelor [loading dose], compared with clopidogrel [loading dose], and was maintained up to the 8-h point,” the authors wrote. “The number of patients with HPR was significantly lower with ticagrelor than with clopidogrel.”
The study included 100 P2Y12 inhibitor-naïve patients with biomarker-negative ACS who underwent ad hoc PCI. Patients were randomly assigned to receive either ticagrelor 180 mg loading dose or clopidogrel 600 mg loading dose.
Researchers measured platelet reactivity, defined by P2Y12 reaction units (PRU), before the loading dose was administered, at 0.5, 2, and 8 hours after the loading dose, and at the end of PCI. The primary end point was PRU levels 2 hours after the loading dose was administered, and secondary end points included the other time points and inhibition of platelet aggression. An exploratory analysis was conducted to evaluate the rates of HPR.
When researchers compared ticagrelor and clopidgrel, the PRU levels diverged as early as 0.5 hours. At 2 hours, ticagrelor lowered PRU levels significantly compared with clopidogrel (98.4 ± 95.4 vs 257.5 ± 74.5; P<.001). Researchers also observed differences by the end of PCI, with a mean of 0.6 hours after the loading dose, which was maintained up to 8 hours after the loading dose.
HPR rates were also significantly reduced with ticagrelor compared with clopidogrel at the end of PCI (P=.030), at 2 hours after loading dose (P<.001), and at 8 hours after loading dose (P<.001).
The authors noted that their findings confirmed the observation made in previous investigations under different clinical settings: the superior potency of ticagrelor’s superior potency over clopidogrel.
“Prospective studies are needed to establish the optimal time to administer P2Y12 receptor antagonists in patients with unstable angina, once the results of diagnostic coronary angiography prompt a decision to perform PCI,” they concluded.
Angiolillo DJ, Franchi F, Waksman R, et al. Effects of ticagrelor versus clopidogrel in troponin-negative patients with low-risk ACS undergoing ad hoc PCI. J Am Coll Cardiol. 2016; 67(6):603-613. doi: 10.1016/j.jacc.2015.11.044.