Can my Medicare Part D plan change the plan's pharmacy network during the plan year?

Yes. Medicare prescription drug plans (PDP and MAPD) have the right to add or drop participating pharmacies from the plan's pharmacy network throughout the plan year - or change a pharmacy’s standard / preferred network pharmacy status.

Can I get a Special Enrollment Period to change Medicare Part D plans if my only local pharmacy is dropped from the pharmacy network?

Probably not. Medicare does not provide an established Special Enrollment Period (SEP) when a Medicare plan changes your pharmacy network (although there is an SEP available when Medicare Advantage plans make substantial changes to their healthcare network). In most cases, you will need to wait until the Annual Open Enrollment Period (AEP) to change Medicare Part D plans (starting October 15th and continuing through December 7th) - or if you have a Medicare Advantage plan that includes drug coverage (MAPD), you can use the Medicare Advantage Open Enrollment Period (MA OEP) to change Medicare Advantage plans (starting January 1st and continuing through March 31st).

However, Medicare does have the ability to grant Special Enrollment Periods for "exceptional conditions" or "extraordinary circumstance beyond [the person's] control" (such as fraudulent enrollment or misleading marketing practices) - and you can telephone a Medicare representative at 1-800-633-4227 and ask whether your situation qualifies you for such an SEP.

For more information about mid-year pharmacy changes, you can refer to your Medicare plan's 200+ page Evidence of Coverage (EOC) document that you were mailed when you enrolled in your plan or you can download from your Medicare plan's website.
For example, you may see a section in your EOC such as:

"What if the pharmacy you have been using leaves the network?

If the pharmacy you have been using leaves the plan’s network, you will have to find a new pharmacy that is in the network. Or if the pharmacy you have been using stays within the network but is no longer offering preferred cost-sharing, you may want to switch to a different pharmacy. To find another network pharmacy in your area, you can get help from Customer Service (phone numbers are printed on your Member ID card and on the cover of this EOC document) or you can refer to the printed Healthcare Provider and Pharmacy Directory. You can also find information on our [Medicare plan] website at https://[Your Medicare plan's website]"

The good news.
Most all Medicare Part D prescription drug plans will have 50,000 to 65,000+ participating pharmacies within the plan’s pharmacy network - plus often a mail-order option – so even with mid-year pharmacy changes, you should not have difficulty having your prescriptions filled – and during the plan year you may even find more local pharmacies being added to your plan’s pharmacy network.

As reference, please see:
Medicare Prescription Drug Benefit Manual, Chapter 3 - Eligibility, Enrollment and Disenrollment, Updated: August 19, 2011 (Revised: August 15, 2023)