The high cost of multiple sclerosis (MS) disease-modifying therapies can negatively affect access for patients through increased payer restrictions and higher out-of-pocket spending. Our objective was to describe changes in pharmacy benefit coverage and cost-sharing amounts for MS disease-modifying therapies in the Medicare Part D program, using enrollment-weighted Prescription Drug Plan Formulary files for the period 2007–16. Among therapies available throughout the study period, the rate of prior authorization use increased from 61–66 percent of plans to 84–90 percent. The share of plans with at least one therapy available without limitations declined from 39 percent to 17 percent. The projected cumulative out-of-pocket spending for 2019 was $6,894. The therapy with the highest out-of-pocket spending was generic glatiramer acetate. Policy makers need to consider both access restrictions and a growing cost-sharing burden as potential consequences of high and rising drug prices for people with MS.