Purpose: High on-treatment platelet reactivity (HTPR) after clopidogrel administration in patients with acute coronary syndrome (ACS) has been associated with an increased risk of adverse events. Our previous studies reported that half-dose ticagrelor provides a similar inhibitory effect on adenosine diphosphate (ADP)-induced platelet aggregation as standard-dose ticagrelor, but half-dose of ticagrelor has not been studied in Chinese ACS patients with HTPR. This study aimed to compare the antiplatelet action of half-dose ticagrelor with high-dose clopidogrel in ACS patients with HTPR.
Methods: In this single-center randomized controlled trial, 80 (of 418 screened, 19.13%) ACS patients with HTPR while on clopidogrel were randomized to either half-dose ticagrelor (90 mg LD, then 45 mg twice daily) or high-dose clopidogrel (150 mg once daily). Platelet function was assessed by thromboelastography (TEG) and light transmission aggregometry (LTA), and adverse events were monitored throughout the study for 30 days.
Results: The ADP-induced platelet inhibition rate (IR) as measured by TEG was significantly higher for half-dose ticagrelor compared with high-dose clopidogrel (70.40% [61.10%-91.70%] vs. 44.25% [34.67%-79.07%], p = 0.001). The repeated HTPR rate was dramatically higher for high-dose clopidogrel compared with half-dose ticagrelor (6 of 32, 18.75% vs. 1 of 35, 2.85%; p = 0.04). No patients in either treatment group exhibited a major bleeding event or other adverse events.
Conclusions: In ACS patients with HTPR, half-dose ticagrelor is more effective than high-dose clopidogrel in reducing platelet reactivity (NCT03062462).
Keywords: ACS; Clopidogrel; HTPR; Ticagrelor.