P2Y 12 receptor inhibition with prasugrel and ticagrelor in STEMI patients after fibrinolytic therapy: Analysis from the SAMPA randomized trial.

BACKGROUND: A pharmacodynamic comparison between ticagrelor and prasugrel after fibrinolytic therapy has not yet been performed.

METHODS: In the single-center SAMPA trial, 50 consecutive STEMI patients previously treated with clopidogrel and undergoing a pharmacoinvasive strategy were randomized to either a ticagrelor (n=25) 180mg loading dose followed by 90mg bid, or a prasugrel (n=25) 60mg loading dose followed by 10mg/day, initiated after fibrinolytic therapy but before angiography. Platelet reactivity was assessed with the VerifyNow P2Y12 assay at 0, 2, 6, and 24h after randomization.

RESULTS: Mean times from fibrinolysis to prasugrel or ticagrelor administration were 11.1±6.9 and 13.3±6.3h, respectively (p=0.24). The values of PRU decreased significantly from baseline to 2h (all p<0.001) and from 2h to 6h (all p<0.001) in both groups. There was no difference in PRU values between 6h and 24h. The mean PRU values at 0, 2, 6, and 24h were 234.9, 127.8, 45.4, and 48.0 in the prasugrel group and 233.1, 135.1, 67.7, and 56.9 in the ticagrelor group, respectively. PRU values did not significantly differ between groups at any time period of the study.

CONCLUSIONS: In patients with STEMI treated with fibrinolytic therapy, platelet inhibition after clopidogrel is suboptimal and can be further increased with more potent agents. Ticagrelor and prasugrel demonstrated a similar extent of P2Y12 receptor inhibition within 24h, although maximal platelet inhibition after these potent agents was not achieved for 6h.