NorthPoint Domain

600-mg Loading Dose of Clopidogrel Reduces Infarct Size

The larger dose was also associated with fewer 30-day adverse events

A study published recently in the Journal of the American College of Cardiology found that pre-treating patients with ST-segment elevation myocardial infarction (STEMI) with a 600-mg loading dose of clopidogrel prior to percutaneous coronary intervention (PCI) was associated with a reduced infarct size compared to a 300-mg loading dose. In addition, the larger dose was associated with improvement of angiographic results, residual cardiac function, and 30-day major adverse cardiovascular events.

Although large randomized trials used a 300-mg loading dose of clopidogrel, there is still debate about the adequacy of platelet response to standard doses. Previous studies have suggested that a 600-mg loading dose of clopidogrel may be more effective than a 300-mg dose, but the evidence has been observational. Thus, the authors undertook the ARMYDA-6 MI randomized trial to evaluate a 600-mg loading dose of clopidogrel versus a 300-mg dose of clopidogrel in terms of efficacy and safety outcomes in urgent PCI for STEMI.

A total of 201 patients with STEMI undergoing primary PCI were randomly assigned to receive a 600-mg (103) or 300-mg (98) clopidogrel loading dose before the procedure. The primary endpoint was the evaluation of infarct size under the curve of cardiac markers. Infarct size was smaller in the 600-mg group. Thrombolysis in myocardial infarction (TIMI) flow grade of more than one at diagnostic coronary angiography before PCI was found in 21.4 percent of patients in the 600-mg group compared to 12.2 percent in the 300-mg group, whereas a lower incidence of TIMI flow grade of less than 3 was associated with the 600-mg group. Although left ventricular ejection fraction early after PCI was similar in the two groups, it was higher in the 600-mg group at discharge. The 600-mg group also had a reduced occurrence of 30-day major adverse cardiovascular events compared to the 300-mg group.

Source: Patti G, Barczi G, Orlic D, et al. 2011. Outcome comparison of 600- and 300-mg loading dose of clopidogrel in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: results from the ARMYDA-6 MI (Antiplatelet therapy for Reduction of MYocardial Damage during Angioplasty-Myocardial Infarction) randomized study. Journal of the American College of Cardiology 58(15):1592-1599.