Patterns of antiplatelet drug use after a first myocardial infarction during a 10‐year period

AIMS The aims of the present study were to assess antiplatelet drug use patterns after a first myocardial infarction (MI) and to evaluate the determinants of antiplatelet nonpersistence. METHODS The present study was conducted in 4690 patients from the Utrecht Cardiovascular Pharmacogenetics cohort with a first MI between 1986 and 2010, who were followed for a maximum of 10 years. Medication use and event diagnosis were obtained from the Dutch PHARMO Record Linkage System. Antiplatelet drug users were classified as persistent users (gap between prescriptions ≤90 days), nonpersistent users (>90-day gap and no refills), and restarters (a new prescription after a >90-day gap). The association between potential determinants and antiplatelet nonpersistence was analysed using Cox regression. RESULTS The proportions of persistent users decreased from 84.0% at the 1-year follow-up to 32.8% at 10 years for any antiplatelet drug, and 77.3% to 27.5% for aspirin; and 39.0% to 6.4% for clopidogrel at 6 years. Most nonpersistent users restarted antiplatelet drugs later, leading to 89.3% overall antiplatelet drug users at 10 years after MI. Diabetes (hazard ratio [HR] 0.44; 0.32-0.60), hypertension (HR 0.77; 0.60-0.99), hypercholesterolaemia (HR 0.49; 0.39-0.62) and more recent MI diagnosis period (2003-2007: HR 0.69, 0.61-0.79; 2008-2010: HR 0.38, 0.19-0.77, compared to ≤ 2002 period) lowered the risk of antiplatelet nonpersistence, while vitamin K antagonist (VKA) comedication (HR 18.97; 16.91-21.28) increased this risk. CONCLUSIONS A large proportion of patients with a first MI still used antiplatelet drugs after 10 years. The frequent discontinuations during this time frame are expected to reduce the effectiveness of antiplatelet drugs as secondary prevention of cardiovascular diseases. Diabetes, hypertension, hypercholesterolaemia, VKA comedication and MI diagnosis period were determinants of antiplatelet nonpersistence.