CARDIOVASCULAR NEWS

600-mg Clopidogrel Loading Dose Reduces Non-Responsiveness and Post-Treatment Platelet Aggregation in Patients Undergoing Coronary Stenting

Nonresponsiveness (NR) to clopidogrel has been reported after a 300-mg loading dose, hence, the relation of clopidogrel dose, the incidence of NR, and high post-treatment platelet aggregation (PA) in patients undergoing coronary stenting was studied.

Clopidogrel responsiveness and post-PA were measured in patients undergoing stenting (n = 190) randomly treated with either a 300-mg or a 600-mg clopidogrel load. Nonresponsiveness was defined as <10% absolute change in platelet aggregation, and high post-PA was defined as >75th percentile aggregation after 300 mg clopidogrel.

Nonresponsiveness was lower after 600 mg compared to the 300-mg dose (8% vs. 28% and 8% vs. 32% with 5 and 20 µM ADP, respectively, p < 0.001). Among the patients with high post-PA after 300 mg clopidogrel, 62% to 65% had NR, whereas after the 600-mg dose, all of the patients with high post-PA had NR.

The study concluded that a 600-mg clopidogrel loading dose reduces the incidence of NR and high post-PA as compared to a 300-mg dose. Investigators suggest higher dosing strategies and methods to confirm platelet inhibition should be further investigated in order to optimally use clopidogrel in patients undergoing stenting.

J Am Coll Cardiol. 2005 45:1392-1396