Drug utilization patterns and cardiovascular outcomes in elderly patients newly initiated on atorvastatin or simvastatin

Abstract

Background: Hydroxymethylglutaryl coenzyme-A reductase inhibitors simvastatin and atorvastatin are effective at lowering LDL-C levels and reducing the risk of cardiovascular (CV) events.

Objective: The objective of this study was to examine differences in drug utilization and CV event risk among elderly patients newly initiated on simvastatin versus atorvastatin.

Methods: This was a retrospective analysis using pharmacy and medical claims from a US health plan database. Enrollees aged ≥65 years, newly initiated on simvastatin or atorvastatin (index drugs) from July 1, 2006 to November 30, 2008 were identified for study inclusion. Patients were excluded if they had any prescriptions for clopidogrel, nitrates, or other dyslipidemia medication, or any CV events before index drug initiation. Adherence was calculated by proportion of days covered with index medication. CV events (myocardial infarction, ischemic heart disease, cerebrovascular disease, peripheral vascular disease, aortic aneurysm, revascularization, or heart failure) were identified from medical claims.

Results: There were 11,470 atorvastatin initiators and 20,132 simvastatin initiators identified. Mean age of these patients was 72 years; 40% were male; nearly half had hypertension; and more than a quarter had diabetes. The majority of statin therapy (77%) was prescribed by primary care physicians. Forty-nine percent of atorvastatin patients were initiated on a 10 mg-dose and 61% of simvastatin patients on 5-, 10-, or 20-mg doses. A larger percentage of patients in the simvastatin cohort were adherent to index therapy than patients in the atorvastatin cohort (43% vs 36%, respectively). Multivariate regression adjusting for patient characteristics revealed no significant difference in CV events between patients receiving atorvastatin versus simvastatin.

Conclusions: In this study of elderly statin patients without recent evidence of CV events, the majority of patients started on low-dose therapy and did not achieve sufficient adherence. After controlling for patient and clinical characteristics, no statistically significant difference in risk of CV event was observed based on initiation with atorvastatin versus simvastatin.