Ensuring Seniors Access to Local Pharmacies Act of 2017 This bill modifies requirements regarding access to preferred pharmacies (i.e., pharmacies that provide reduced enrollee cost sharing for prescription drugs) under a Medicare prescription drug plan (PDP). Specifically, if a Medicare PDP has, in its pharmacy network, one or more preferred pharmacies located in a health shortage or medically underserved area, then the PDP sponsor must allow any pharmacy in the health shortage or medically underserved area to join the preferred pharmacy network under comparable terms and conditions.