The effect of prescription drug insurance on the incidence of potentially inappropriate prescribing: evidence from Medicare Part D

The Medicare Part D program has been documented to increase the affordability and accessibility of drugs and improve the quality of prescription drug use; however, less is known about the equity impact of the Part D program on potentially inappropriate prescribing—specifically, incidences of polypharmacy and potentially inappropriate medication (PIM) use based on different racial/ethnic groups. Using a difference in the regression discontinuity design, we found that among Whites, Part D was associated with increases in polypharmacy and “broadly defined” PIM use, while the use of “always avoid” PIM remained unchanged. Conversely, Blacks and Hispanics reported no changes in such drug utilization patterns.