RESUMO
OBJECTIVE: There is a paucity of data regarding the early effectiveness of the proposed 600 mg clopidogrel loading dose (LD) on platelet reactivity (PR) in ST elevation myocardial infarction (STEMI) patients. If high on-treatment platelet reactivity (HTPR) is present, prasugrel reloading and subsequent maintenance dose (MD), might offer faster and stronger platelet inhibition than high clopidogrel MD. METHODS: In 93 STEMI patients treated by primary percutaneous coronary intervention we assessed PR using the VerifyNow P2Y12 platelet function test, 2 h following 600 mg LD of clopidogrel. All the 60 (64.5 %) patients exhibiting HTPR (defined as PR ≥ 235 P2Y12 reaction units), were randomized to 1 of 2 therapeutic strategies: reloading with prasugrel 60 mg/10 mg MD or high (150 mg) clopidogrel MD. RESULTS: The primary endpoint of PR at 24 h post randomization was lower in the prasugrel compared to the clopidogrel group (51.3, 25.7-77.0 versus 242.4, 215.8-268.9 P2Y12 reaction units, least square estimates, 95 % confidence intervals, p < 0.001). PR at 2 h and 5 days post randomization was lower in the prasugrel compared to the clopidogrel group (117.2, 70.9-163.4 and 101.6, 70.1-133.2 least square mean difference, 95 % confidence intervals, p < 0.001 for both). At all the time points of PR assessment, HTPR rates were lower in prasugrel than in clopidogrel group. CONCLUSIONS: HTPR is commonly observed early post 600 mg clopidogrel LD in STEMI patients. In this case, prasugrel 60 mg LD/10 mg MD provides faster and stronger platelet inhibition than a high clopidogrel MD regimen.
