Background: Clopidogrel is widely used in coronary intervention. However, due to the delayed onset and variable responsiveness to this drug, European guideline had recommended to use prasugrel or ticagrelor in stead of clopidogrel in patients with acute coronary syndrome. There is little data about pharmacokinetic and phamacodynamic effect of prasugrel in Korean population. Objective: We sought to determine pharmacokinetic and phamacodynamic effect in Korean normal volunteer after the loading dose (LD) of 30 mg prasugrel and 600 mg clopidogrel. Methods: We randomly assigned either prasugrel group (pra-G) and clopidogrel group (clo-G) in 12 patients (6 in each group) and switched to the other group in 2 weeks later. We had serially measured active metabolites of both drugs for 24 hours (baseline, 0.5, 1, 2, 4, 6, 12, 24 hr after taking single LD of each drug. We also measured platelet function (light transmission aggregometry, VeryfyNow and multiple electrode aggregometry) at baseline and 0.5, 2, 6 and 24 hour after LD. Results: All volunteers are male and mean age was 24.9짹1.6 yrs. Baseline mean maximal platelet aggregation (MPA) on ADP 10 關M was not different (pra-G 82% vs clo-G 74 %, p>0.05), but was significantly different from half an hour after taken each drug (pra-G 21% vs clo-G 59%, p<0.05), 2 hr (5% vs 19%, p<0.05), 6 hr (7% vs 22%, p<0.05) as well as 24 hr (13% vs 26%, p<0.05). Baseline PRU values of VeryfyNow was similar in both groups (pra-G 365 vs clo-G 348, p>0.05) and was significantly different after 0.5, 2, 6 and 24 hr after single LD medication (135 vs 307, 47 vs 164, 51 vs 172, 40 vs 158, all p<0.05 ). Similar results were observed with multiple electrode aggregometry. Inhibition of platelet activity (IPA) and VeryfyNow data was shown in fig. 1a and 1b. Conclusion: Prasugrel 30 mg LD resulted in more rapid and potent inhibition of platelet function than clopidogrel 600 mg LD. Active metabolite concentration of both drugs and their relationships of platelet inhibition will be presented.