Association Between Pharmacy Benefit Restrictions and Disease-Modifying Therapy Use in the Medicare Part D Program.

Background and Objectives: To determine the association between Medicare Part D plan disease-modifying therapy (DMT) restrictiveness and adherence and outcomes among people with multiple sclerosis (MS). Methods: We used Medicare claims data from 2010 to 2014 to identify individuals with a full year enrollment (Parts A, B, and D), an MS diagnosis, and 1 or more self-administered DMT prescription. Plans were considered restrictive if all available DMTs required a prior authorization or step therapy restriction; otherwise they were considered permissive. We compared DMT adherence, defined as a medication possession ratio ≥80%, MS-related emergency department or inpatient admissions, and outpatient visits by Part D plan restrictiveness. We used multivariate regression models to control for patient demographics and comorbidities. Results: There were 37,713 Medicare beneficiaries with MS who were enrolled in either restrictive (n = 29,901) or permissive (n = 7812) Part D plans during the study period. Patients enrolled in restrictive plans were older (60 vs 58 years; Discussion: Medicare beneficiaries with MS enrolled in restrictive Part D plans were less adherent to their DMT and had higher rates of MS-related outpatient visits.