Effect of a high loading dose of clopidogrel on platelet function in patients undergoing coronary stent placement

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Abstract
Following coronary stent placement, platelet activation is a major determinant of the risk of subacute stent thrombosis.1 Combined antiplatelet treatment with ticlopidine and aspirin reduced platelet activation after coronary stenting1. Although combined antiplatelet treatment consisting of aspirin and ticlopidine has significantly reduced early ischaemic events following coronary stenting, stent thrombosis still occurs in up to 1% of treated patients, especially in the early days after the intervention, probably because of delayed onset of action of ticlopidine. Clopidogrel is a ticlopidine-like novel thienopyridine inhibitor of ADP induced platelet activation.2 Clopidogrel differs from ticlopidine in that it has a favourable safety profile compared to ticlopidine and reveals an accelerated antiplatelet activity after first administration. The present study sought to investigate the antiplatelet effect of various doses of clopidogrel in patients undergoing coronary stent placement; comparison was made with standard ticlopidine treatment. Thirty patients were randomised into three treatment arms: group I (n = 10), ticlopidine 2 × 500 g as loading dose and 2 × 250 mg daily thereafter; group II (n = 10), clopidogrel 1 × 300 mg loading dose and 1 × 75 mg per day; or group III (n = 10), clopidogrel 1 × 600 mg plus 2 × 75 mg daily thereafter. All patients received aspirin 2 × 100 mg per day concomitantly. Peripheral venous blood samples were taken with a loose tourniquet through a short venous catheter inserted into a forearm vein before and then 2, …