Medicaid prescription drug utilization and expenditures following Part D.

Although much attention has been paid to examining the impact of Medicare Part D on Medicare, few studies have examined its influence on Medicaid. This study uses an interrupted time series design to examine the impact of Part D on prescription drug expenditures and utilization among different therapeutic classes of medication across 44 Medicaid programs. In overall reductions in Medicaid prescription expenditures and utilization, our study finds evidence of greater reductions among medications used to treat chronic conditions. Our results provide a glimpse of the impact of Part D on long-term growth in the Medicaid prescription drug benefit.