Preferred drug lists and Medicaid prescriptions

When Medicaid preferred drug lists (PDLs) are implemented, they may impose indirect costs on prescribing physicians and Medicaid patients, leading to an unintended reduction in the number of Medicaid prescriptions filled.

To test retrospectively the proposition that PDLs adversely affect the number of Medicaid prescriptions filled.

We compared three 'test' states (Alabama, Texas, and Virginia) that implemented PDLs with restrictions on the prescription of statins with three 'control' states (New Jersey, North Carolina, and Pennsylvania) that did not implement drug access restrictions. We conducted the analysis at the county level and used a differences-in-differences approach that allows for county and time-period fixed effects.

We found that PDLs adversely impacted several measures of filled Medicaid prescriptions in the 'test' states relative to the 'control' states.

There are unintended but potentially harmful consequences to cost-focused health policy interventions.