Impact of patient and plan design factors on switching to preferred statin therapy

Changing formulary status is a common strategy to encourage greater use of lower-cost brand and generic drugs.

To examine the relationship between patient and plan design factors and formulary adherence after the formulary status change of atorvastatin.

We conducted a cross-sectional, cohort study of patients enrolled in one of 2139 commercial (no Medicare or Medicaid) plans that offer a 3-tier benefit design and changed atorvastatin from formulary to nonformulary status on January 1, 2006. Adults on atorvastatin therapy who were receiving targeted communications in the fourth quarter of 2005 were included for analysis. We used bivariate and multivariate logistic regression analyses to examine the relationship between covariates and formulary adherence for patients receiving atorvastatin through retail or home delivery (HD) pharmacies.

A total of 211,083 patients met the study inclusion criteria, and more than 42% switched from atorvastatin to a formulary statin (33.1% retail, 51.8% HD). Patient-related factors that consistently and positively predicted switching across retail and HD channels included female sex, prior statin switching, and member outreach to the pharmacy benefit manager through telephone or Web use. Plan design factors that positively influenced switching to the preferred agent included step therapy, brand preferred/nonpreferred copayment differential, and among retail users, receipt of a rapid response education letter. Adoption of step therapy and the rapid-response program in retail settings increased the odds of switching by 1.3. Compared with patients who were paying a differential of $10 or less in retail channels, those who were paying $11-15, $16-20, and $21 and higher had increased odds of switching of 35% (95% CI 1.31 to 1.39), 41% (95% CI 1.37 to 1.46), and 80% (95% CI 1.74 to 1.86), respectively. In HD, compared with patients who were paying a differential of $15 or less, those who were paying $16-30, $31-40, and $41 and higher had increased odds of switching to a formulary preferred agent of 20% (95% CI 1.17 to 1.23), 23% (95% CI 1.19 to 1.26), and 59% (95% CI 1.55 to 1.64), respectively.

Through appropriate program and plan design, plan sponsors' impact on formulary adoption is maximized.