Clopidogrel Adherence following Percutaneous Coronary Intervention with a Drug-Eluting Stent in a VA Medical Center

Abstract

Background: Antiplatelet therapy with aspirin and a thienopyridine is the standard of care for prevention of thrombosis following coronary stent implantation. Recent evidence suggests a prolonged risk of stent thrombosis; therefore, clopidogrel therapy for at least 1 year is recommended following implantation of a drug-eluting stent. Premature discontinuation of clopidogrel is a well-recognized risk factor for stent thrombosis. Objective: To identify the rate of adherence to clopidogrel therapy among patients who have undergone percutaneous coronary intervention (PCI). Methods: We queried the central Veteran Affairs (VA) pharmacy database for each patient who underwent PCI with a drug-eluting stent between September 2004 and August 2005 at a single VA medical center. Based on pharmacy refill records, patients were considered adherent to clopidogrel if they filled more than 80% of the clopidogrel prescriptions. Results: We observed that 20.3% of patients were nonadherent to clopidogrel therapy for the course that they were assigned. Shorter duration of therapy was the only factor that predicted increased adherence. Race, polypharmacy, marital status, prior clopidogrel use, and age did not have a significant impact on adherence. Multivariable analysis did not demonstrate any other significant relationships. Conclusions: In this high-risk cohort of patients who have undergone PCI, we observed a 20% incidence of nonadherence to clopidogrel therapy. Shorter duration of therapy had a significant impact on improving rates of adherence in our analysis. This observation is of particular concern given the recent recommendations to prolong antiplatelet therapy to at least 1 year following PCI with a drug-eluting stent.