Estimating Medicare Part D's impact on medication access among dually eligible beneficiaries with mental disorders

Medicare drug benefit (Part D) plans may restrict psychotropic medications more than state Medicaid programs do. This may have important implications for patients dually eligible for Medicare and Medicaid whose medications previously were covered under Medicaid. The objective of this study was to estimate rates of medication switching among dually eligible beneficiaries using antidepressants, antipsychotics, and mood stabilizers attributable to their enrollment in Medicare drug plans.

Baseline data on medication usage patterns among 467 dually eligible beneficiaries with mental disorders from the Medicare Current Beneficiary Survey, formulary data from a sample of Medicare drug plans, and estimates of the utilization response to pharmacy management tools from the Medicaid literature were used to estimate the likelihood of switching medications conditional on use of drugs and assignment to particular Medicare drug plans.

Restrictions on psychotropic medications were common among the drug plans studied. Estimated rates of medication switching attributable to Medicare Part D were 6%-10% among dually eligible beneficiaries using antipsychotics, 5%-7% among those using antidepressants, and 2%-4% among those using mood stabilizers. Switching rates varied substantially across plans.

On average, relatively few dually eligible beneficiaries with mental disorders are likely to experience treatment disruptions because of formulary restrictions and utilization controls used by Medicare drug plans. However, beneficiaries in some plans will experience significant barriers to medication access. Given the substantial variation among Medicare drug plans' management of psychotropic medication use, clinicians and social service agencies should counsel their beneficiaries with mental disorders in navigating the complex Medicare drug plan market.