BACKGROUND Clopidogrel napadisilate has better clopidogrel stability than clopidogrel bisulfate. There are no data, however, on the antiplatelet efficacy and tolerability of clopidogrel napadisilate in coronary artery disease (CAD) patients.

OBJECTIVE The aim of this study is to demonstrate that the combination therapy of aspirin and clopidogrel napadisilate is not inferior to that of aspirin and clopidogrel bisulfate with respect to its effectiveness in inhibiting platelet aggregation, if it is given for 4 weeks to CAD patients who had been treated with a drug-eluting stent more than 12 months prior and had remained in a stable condition with a single antiplatelet agent, aspirin.

METHODS This study was a prospective, randomized, double-blind, double-dummy, parallel-group, phase IV clinical trial. A total of 162 patients were prospectively recruited from three centers. The subjects were randomized to either the test group that was treated with 75 mg of clopidogrel napadisilate once daily or to the control group that was treated with 75 mg of clopidogrel bisulfate once daily. The primary outcome was the percent inhibition of the platelet aggregation change after the medication, as assessed by a VerifyNow™ P2Y12 assay. The secondary outcome was the change in P2Y12 reaction units (PRUs) from the baseline to the end of 4 weeks of treatment. The prevalence of adverse events was assessed at each visit through a direct interview.

RESULTS The mean increase in the percent inhibition after 4 weeks of treatment was 19.4 % in the clopidogrel napadisilate group and 19.5 % in the clopidogrel bisulfate group. The lower bound of the 95 % two-sided confidence interval for the difference in the change between the two groups (-5.46) was greater than the pre-defined non-inferiority margin of (-10.5). Therefore, clopidogrel napadisilate was deemed non-inferior to clopidogrel bisulfate with respect to its effectiveness in inhibiting platelet aggregation. The PRU decreased by 73.1 ± 30.7 in the clopidogrel napadisilate group, which decreased by -7.8 more than in the clopidogrel bisulfate group (65.3 ± 62.1); but the difference between the two groups was statistically insignificant (p = 0.435). There was no significant difference in the drug-related adverse events between the two groups (12.3 vs. 10.1 %; p = 0.804).

CONCLUSION The platelet inhibitory efficacy of clopidogrel napadisilate is not inferior to that of clopidogrel bisulfate. There were also no statistically significant differences between the two treatment groups in the safety analyses. Therefore, clopidogrel napadisilate can be a suitable alternative to clopidogrel bisulfate in stable CAD patients who have undergone a drug-eluting stent placement.

CLINICAL TRIAL REGISTRATION Registered at ClinicalTrials.gov as NCT01830491.