Objective: To evaluate the effects of patient copayment and coinsurance policies on adherence to therapy with beta-adrenergic blocking agents (beta-blockers) and on the rate of initiation of beta-blocker therapy after acute myocardial infarction (MI) in a population-based natural experiment.
Study design: Three sequential cohorts included British Columbia residents age 66 years and older who initiated beta-blocker therapy during time intervals with full drug coverage (2001), a $10 or $25 copayment (2002), and 25% coinsurance (2003-2004). We used linked data on all prescription drug dispensings, physician services, and hospitalizations. Follow-up of each cohort was 9 months after the policy changes.
Methods: We measured the proportion of subjects in each cohort who were adherent to beta-blocker therapy over time, with adherence defined as having >80% of days covered. We also measured the proportion of patients initiating beta-blocker therapy after acute MI. Policy effects were evaluated using multivariable regression.
Results: Adherence to beta-blocker therapy was marginally reduced as a consequence of the copayment policy (-1.3 percentage points, 95% confidence interval [CI] = -2.5 , -0.04) or the coinsurance policy (-0.8 percentage points, 95% CI = -2.0, 0.3). The proportion of patients initiating beta-blockers after hospitalization for acute MI remained steady at about 61% during the study period, similar to that observed in a control population of elderly Pennsylvania residents with full drug coverage.
Conclusions: Fixed patient copayment and coinsurance policies had little negative effect on adherence to relatively inexpensive beta-blocker therapy, or initiation of beta-blockers after acute MI.