Prevalence, predictors, and outcomes of primary nonadherence after acute myocardial infarction

Secondary prevention after acute myocardial infarction (AMI) is achieved primarily through medications. However, patients must take their medications to benefit. Medication adherence research has focused primarily on continuation of medications rather than not filling the first prescription written (primary nonadherence). Our objectives were to characterize, to determine factors of, and to measure outcomes associated with primary nonadherence after AMI.

We conducted a population-based cohort study using an AMI registry linked with administrative data in Ontario, Canada. The primary outcome was 1-year mortality. There were 4591 post-AMI patients >65 years of age included with 12 832 prescriptions written, of which 73% and 79% were filled within 7 and 120 days, respectively. By 120 days after discharge, more cardiac than noncardiac prescriptions were filled (82% versus 35%, respectively; P<0.0001). Only 74% of patients filled all their discharge prescriptions by 120 days after discharge after the exclusion of acetylsalicylic acid, which is also available over the counter in Ontario. Factors associated with filling all compared with filling no discharge prescriptions included younger age, low income, discharge medication counseling, in-hospital attending cardiologist, and fewer medications before AMI. The adjusted 1-year mortality rate was higher in patients who filled some versus all (odds ratio, 1.44; 95% confidence interval, 1.15 to 1.79; P=0.001) and none versus all (odds ratio, 1.80; 95% confidence interval, 1.35 to 2.42; P<0.0001) of their discharge medications.

Patients fill most of their discharge prescriptions within 1 week after AMI. The 1-year mortality rate was higher for those patients who did not fill all of their discharge medications after AMI. Factors such as discharge medication counseling and postdischarge follow-up may help to increase the filling rate of medications after AMI.