Suboptimal Statin Adherence and Discontinuation in Primary and Secondary Prevention Populations: Should We Target Patients with the Most to Gain?

OBJECTIVES: To compare statin nonadherence and discontinuation rates of primary and secondary prevention populations and to identify factors that may affect those suboptimal medication-taking behaviors. DESIGN: Retrospective cohort utilizing pharmacy claims and administrative databases. SETTING: A midwestern U.S. university-affiliated hospital and managed care organization (MCO). PATIENTS: Non-Medicaid MCO enrollees, 18 years old and older, who filled 2 or more statin prescriptions from January 1998 to November 2001; 2,258 secondary and 2,544 primary prevention patients were identified. MEASUREMENTS: Nonadherence was assessed by the percent of days without medication (gap) over days of active statin use, a measurement known as cumulative multiple refill-interval gap (CMG). Discontinuation was identified by cessation of statin refills prior to the end of available pharmacy claims data. RESULTS: On average, the primary and secondary groups went without medication 20.4% and 21.5% of the time, respectively (P = .149). Primary prevention patients were more likely to discontinue statin therapy relative to the secondary prevention cohort (relative risk [RR], 1.24; 95% confidence interval [CI], 1.08 to 1.43). Several factors influenced nonadherence and discontinuation. Fifty percent of patients whose average monthly statin copayment was <$10 discontinued by the end of follow-up (3.9 years), whereas 50$10 but. $20 and >$20 discontinued by 2.2 and 1.0 years, respectively (RR, 1.39 and 4.30 relative to <$10 copay, respectively)