Objectives To compare the short-term efficiency and safety of high loading dose (600 mg) clopidogrel pretreatment with that of routine loading dose (300 mg) before emergent percutaneous coronary intervention (PCI) in patients with acute myocardial infarction (AMI).

Methods 60 patients with AMI were divided into 600 mg group and 300 mg group randomly between January 2007 and December 2009. The two groups received 600 mg or 300 mg clopidogrel respectively before undergoing emergent PCI. The incidence of major cardiovascular events (including subacute in-stent thrombosis, death, myocardial infarction, urgent target vessel revascularisation) and hemorrhagic events were followed up to 28 days after the procedure.

Results The incidence of major cardiovascular events in 600 mg group was significantly less than that in 300 mg group (3.3% vs 20.0%, P < 0.05). The occurrence of bleeding events between the two groups had no significant difference (20.0% vs 13.3%,P > 0.05).

Conclusions Compared with the routine 300 mg loading dose, 600 mg high loading dose of clopidogrel as pretreatment before emergent PCI in patients with AMI is safe and more efficient in improving clinical outcomes in 28 days after stenting.