The Impact of Coverage Restrictions on Antipsychotic Utilization Among Low-Income Medicare Part D Enrollees

Prior research demonstrates substantial access problems associated with utilization management and formulary exclusions for antipsychotics in Medicaid, but the use and impact of coverage restrictions for these medications in Medicare Part D remains unknown. We assess the effect of coverage restrictions on antipsychotic utilization in Part D by exploiting a unique natural experiment in which low-income beneficiaries are randomly assigned to prescription drug plans with varying levels of formulary generosity. Despite considerable variation in use of coverage restrictions across Part D plans, we find no evidence that these restrictions significantly deter utilization or reduce access to antipsychotics for low-income beneficiaries.