Geographical Access to Preferred Pharmacies in Medicare Part D

Objective: To examine geographic access to preferred pharmacies in Medicare Part D prescription drug plans (PDPs) and Medicare Advantage PDPs (MAPDs).

We conducted a nationwide, retrospective analysis using Part D preferred pharmacies' data, Zip Code Tabulation Areas (ZCTAs) from the US census, and socioeconomic characteristics from the American Community Survey and the Area Health Resources Files from 2010 to 2024.

We computed mean distance from the centroid of each ZCTA to the nearest preferred pharmacy in stand-alone PDPs and in MAPDs. We compared mean distance as well as additional distance to a preferred vs a nonpreferred pharmacy, across rural and urban ZCTAs, and across geographic areas with relatively high densities of different racial/ethnic groups. We employed regression models to evaluate the association between ZCTA-level characteristics and additional distance to a preferred pharmacy.

Rural areas in the West North Central, Mountain, and East South Central divisions of the US tended to lack preferred pharmacies in PDPs and MAPDs, as did some urban areas. Among ZCTAs with preferred pharmacies, a rural ZCTA was associated with a 0.734-mile longer additional distance ( P  < .01) among PDPs, which was more than double the mean additional distance. For MAPD plans, the additional distance for rural ZCTAs was 0.320 miles longer ( P  < .01), an 80% increase relative to the mean.

Many rural and urban areas in the US lack preferred pharmacies. In areas with preferred pharmacies, distances were generally minimal relative to the cost savings, but rural-urban disparities persist.