Effect of 450-mg loading dose of clopidogrel on platelet function in Japanese patients undergoing coronary stent placement.

Usefulness of higher (>300 mg) loading doses of clopidogrel has been demonstrated in studies from the United States and Europe. The present study evaluated platelet aggregation after the administration of a 450-mg loading dose of clopidogrel in Japanese patients undergoing coronary stenting. Platelet aggregation was serially measured at baseline, and 2, 4, 6, and 8 h after 450-mg clopidogrel loading in 25 patients undergoing coronary stenting. Platelets were stimulated with 5 and 20 micromol/l adenosine diphosphate (ADP) and aggregation was assessed by optical aggregometry. Platelet aggregation (5 micromol/l ADP 42.8% +/- 13.5% and 20 micromol/l ADP 51.2% +/- 11.6%) was significantly suppressed <or=4 h after 450-mg clopidogrel loading. There were no adverse events except one minor nasal bleed. The present study shows that platelet inhibition is achieved <or=4 h after the administration of a 450-mg clopidogrel loading dose in Japanese patients.