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

To determine the association between Medicare Part D plan disease-modifying therapy (DMT) restrictiveness and adherence and outcomes among people with multiple sclerosis (MS).

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.

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; p < 0.001), more likely to live in the south (38% vs 23%; p < 0.001), eligible through disability (67% vs 60%; p < 0.001), and more likely to have several chronic comorbid conditions. Patients enrolled in restrictive plans were less likely to be adherent to their DMT (54% vs 57%; p < 0.001; adjusted odds ratio [aOR] 0.92, 95% confidence interval [CI] 0.88-0.98) and had a higher rate of MS-related outpatient visits (1.7 vs 1.4 per year; p < 0.001; aRR 1.27, 95% CI 1.23-1.31).

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.