Comparison of antiplatelet effect of loading dose of clopidogrel versus abciximab during coronary intervention

Randomized clinical trials have evidently shown that the addition of thienopyridines or abciximab to standard aspirin results in a significant reduction of ischaemic complications after coronary stent implantation. A head-to-head comparison of these antithrombotic drug regimens during coronary intervention is, however, lacking, and this was the main aim of the present study. Thirty-nine patients with angina pectoris who were scheduled for coronary stent implantation were assigned to either group 1 (160 mg aspirin + 500 mg ticlopidine post-stent), group 2 (160 mg aspirin + abciximab + 500 mg ticlopidine post-stent) or group 3 (160 mg aspirin + loading dose (375/450 mg) clopidogrel pre-stent and 75 mg clopidogrel post-stent). A loading dose of 450 mg clopidogrel was found to be more effective than the standard loading dose of 375 mg. Platelet aggregation induced by 4 mumol/l adenosine diphosphate (ADP) was assessed in samples collected before intervention and 10 min, 4 h and 20 h after intervention. Before intervention, a moderate antiplatelet effect because of aspirin intake was observed (ADP aggregation level, +/- 50%) in all study groups. After intervention, platelet aggregation tended to be enhanced in group I while it was strongly inhibited in the groups pre-treated with clopidogrel or abciximab: ADP induced an aggregation level early after intervention of 60 +/- 12% in group 1 (ticlopidine post-stenting) versus 30 +/- 10% in group 3 (loading dose clopidogrel) versus 3 +/- 6% in group 2 (abciximab). Abciximab achieved a more complete inhibition of aggregation than clopidogrel (P = 0.007). The overall complication rate was low with only one major bleeding and one death due to side-branch occlusion with re-infarction occurring, both in the abciximab group. Platelet aggregation during coronary intervention is strongly inhibited by both abciximab and by high loading dose of clopidogrel. Although abciximab showed a stronger antiplatelet effect than clopidogrel, it remains to be established whether this ex vivo superiority of abciximab also translates into an overall clinical benefit in patients with elective stent implantation.