Prasugrel has a faster onset of action and greater platelet inhibition with less inter-individual response variability than clopidogrel. Japan and Taiwan are the only two nations where adjusted/Asian dose of prasugrel (loading dose (LD)/maintenance (MD): 20/3.75 mg) was approved for clinical use. However, there is no data regarding the effectiveness of adjusted dose of prasugrel on platelet reactivity in Taiwanese patients with acute coronary syndrome (ACS). This study aim to evaluate the pharmacodynamic of the Asian dose prasugrel on the platelet reactivity after percutaneous coronary intervention (PCI) for patients with ACS.

Rationale and Background Prasugrel provides more potent and rapid platelet inhibition compared to Clopidogrel.

Rapid and effective inhibition of the platelet P2Y12 receptor is of pivotal importance in patients with AMI who undergo PCI.

Prasugrel (60 mg loading and 10 mg/day maintenance dose) is a new generation P2Y12 inhibitor that achieves greater and faster platelet inhibition comparing with clopidogrel in patients undergoing PCI.

As revealed by 2 head-to-head studies, reducing Prasugrel dosages to 20/3.75 LD/MD (mg) was still efficacious but led to less bleeding events than the original 60/10 LD/MD (mg).

In TRITON-TIMI 38 trial, prasugrel was associated with not only significantly less ischemic events but also more non-CABG TIMI major bleeding, as compared to Clopidogrel.

In the PRASFIT-ACS study from Japan (20 mg loading and 3.75 mg/day maintenance dose), prasugrel was associated with a 23% reduction of MACE and the incidence of non-CABG major bleeding was similar to clopidogrel.

There is NO data regarding the effectiveness of Japanese loading dose of prasugrel on platelet reactivity in Taiwanese patients with AMI.

This study use PRU for efficacy and ISTH major bleeding for safety evaluations; the anticipated results are prompt and effective platelet inhibition as well as comparably low bleeding rate.

Inclusion Criteria:

• Age>=20
• Mentally competent to provide an informed consent.
• A person being diagnosed with acute coronary syndrome and arranged for a percutaneous coronary intervention.

Exclusion Criteria:

• A history of hemorrhagic stroke at any time in the past.
• Active internal bleeding or has a history of a bleeding disorder (i.e. hemophilia).
• Severe liver disease; for example, cirrhosis.