[The effect of different loading doses of clopidogrel on platelet aggregation]

To compare the short-term efficacy and safety of high loading dose (600 mg) clopidogrel treatment with those of routine loading dose (300 mg) in patients with acute coronary syndrome and provide evidence for planning clopidogrel treatment.

60 patients were randomized into two groups, One group received 300 mg loading dose clopidogrel, while the other received 600 mg and both were followed by 75 mg daily thereafter. Adenosine diphosphate (ADP) (5 micromol/L and 20 micromol/L) induced platelet aggregation was examined at baseline (before administration), 2 hours and 6 hours after administration and the count of white blood cell and platelet 3 days after loading dose. The primary end points were hemorrhagic events, granulocytopenia and thrombocytopenia within 3 days after administration.

With a high-dose agonist (20 micromol/L ADP), loading doses of clopidogrel at 300 mg and 600 mg both produced greater inhibition of baseline ADP (20 micromol/L) induced aggregation 6 hours after administration than 2 hours [group of 300 mg: (29.75+/-12.11)% vs (43.63+/-14.31)%, P<0.05. Group of 600 mg: (28.86+/-10.24)% vs (34.86+/-10.84)%, P<0.05]. Treatment with clopidogrel at 600 mg loading dose had a marked earlier effect on platelet aggregation 2 hours after administration than that of 300 mg [(34.86+/-10.84)% vs (43.63+/-14.31)%, P<0.05]. The platelet aggregation of the two groups tended towards similar at 6 hours after the procedure [(28.86+/-10.24)% vs (29.75+/-12.11)%, P>0.05]. There were no episodes of hemorrhagic events, granulocytopenia and thrombocytopenia within 3 days after the procedure.

In Chinese patients with acute coronary syndrome platelet aggregation can be inhibited more rapidly and more effectively with clopidogrel at 600 mg loading dose when compared with that at 300 mg loading dose and the safety aspect between the two different loading doses is equivalent.