Efficacy and safety of antiplatelet-combination therapy after drug-eluting stent implantation

Background/Aims: Combination single-pill therapy can improve cost-effectiveness in a typical medical therapy. However, there is a little evidence about the efficacy and tolerability of combination single-pill antiplatelet therapy after percutaneous coronary intervention (PCI) with drug-eluting stents (DES). Methods: From June to November 2012, in total, 142 patients who met the following criteria were enrolled: at least 18 years old successful PCI with DES at least 3 months earlier and regular medication of aspirin and clopidogrel with no side effects. After VerifyNow $P_2Y_{12}$ and aspirin assays, the combination single pill of aspirin and clopidogrel was given and laboratory tests were repeated 6 weeks later. Results: At baseline, the incidence of aspirin resistance, defined as aspirin reaction unit (ARU) ${\geq}550$, was 9.2%, that of clopidogrel resistance, defined as $P_2Y_{12}$ reaction unit (PRU) ${\geq}230$, was 46.5%, and that of percent inhibition of PRU < 20% was 32.4%. At follow-up, the incidence of resistance by ARU value was 7.0%, 50.0% by PRU value, and 35.9% by percentage inhibition of PRU, respectively. The mean values of ARU ($431.5{\pm}63.6$ vs. $439.8{\pm}55.2$; p = 0.216) and PRU ($227.5{\pm}71.4$ vs. $223.3{\pm}76.0$; p = 0.350) were not significantly different before versus after antiplatelet-combination single-pill therapy. Five adverse events (3.5%) were observed during the study period. Conclusions: Combination single-pill antiplatelet therapy, which may reduce daily pill burden for patients after PCI with DES, demonstrated similar efficacy to separate dual-pill antiplatelet therapy.