The association of pre- and posthospital medication adherence in myocardial infarction patients

Background: Nonadherence to optimal medical therapy following myocardial infarction (MI) is associated with adverse clinical outcomes such as stent thrombosis, recurrent cardiovascular events, and death. Whether adherence to medications prior to MI predicts post-MI medication adherence is unknown. Methods: We assessed adherence to P2Y ₁₂ inhibitors and statins before and after admission for MI among 8,147 MI patients who had Medicare insurance with Part D prescription coverage. Adherence was defined as a proportion of days covered with medication fills ≥80%. Multivariable logistic regression was used to assess the association between pre- and post-MI P2Y ₁₂ inhibitor adherence. As few patients were on P2Y ₁₂ inhibitors pre-MI, we also examined the association of pre-MI statin adherence with post-MI P2Y ₁₂ inhibitor and statin adherence. Results: Pre-MI medication nonadherence was observed in 427 of 2,633 (16%) patients on preadmission P2Y ₁₂ inhibitors and 1,233 of 6,934 (18%) patients on preadmission statins. Nonadherent patients were more likely to be of nonwhite race and have multiple prior hospital admissions. Patients who were nonadherent to P2Y ₁₂ inhibitors pre-MI were substantially less likely to adhere to P2Y ₁₂ inhibitors at 90 days (adjusted odds ratio [OR] 0.33, 95% CI 0.25-0.43) and 1 year post-MI (adjusted OR 0.29, 95% CI 0.21–0.39) compared with patients who were adherent pre-MI. Pre-MI statin nonadherence was also associated with lower post-MI adherence to P2Y ₁₂ inhibitors at 90 days (adjusted OR 0.65, 95% CI 0.53-0.79) and 1 year (adjusted OR 0.37, 95% CI 0.29-0.54). Conclusions: Prior medication adherence predicts post-MI adherence to P2Y ₁₂ inhibitors. Increasing accessibility of medication adherence data in the medical record may be an important tool to identify patients at higher risk for post-MI medication nonadherence and target efforts to improve adherence.