Antiplatelet response to the 150-mg maintenance dose of clopidogrel in patients with insufficient platelet inhibition after clopidogrel loading for elective coronary stent placement

Abstract

Our prospective study sought to investigate whether inadequate platelet responses to clopidogrel can be corrected by increasing the daily maintenance dose from 75 mg to 150 mg. In 117 patients with elective PCI after loading with 600 mg clopidogrel, we determined residual platelet aggregation in response to 5 micromol/l ADP (RPA) by optical aggregometry after the first 75 mg maintenance dose (baseline), and at days 14 and 28. In patients with RPA >14% at baseline, we increased the daily dose to 150 mg. Fifty-seven additional patients without dose adjustment served as historic control. In 39 patients with baseline RPA >14%, the increase in maintenance dose to 150 mg reduced median RPA significantly (P<0.001) from 24% [interquartile range: 18-32%] at baseline to 14% [8-20%1 at 14 days without any further significant change. In patients with RPA < or = 14%, who continued on 75 mg clopidogrel, RPA increased during the first 14 days by 4.5% (0-14%; P<0.001). At 14 days, the study group with selective dose adjustment had a significantly lower RPA than the control group without dose adjustment (10.0% [4-20%1 versus 17.0% [9-32%], P<0.001). In patients with a low initial response to clopidogrel, platelet inhibition can be improved by increasing the maintenance dose to 150 mg.