Yes. Your Medicare Part D prescription drug plan's formulary or drug lists can change throughout your coverage year. However, your Medicare Part D plan must provide you with 60 days notice of any changes.
You can use the 60 days to either find an alternative or substitute medication (for instance, you can ask your doctor about a generic medication).
You can also use the 60 days to ask your Medicare Part D plan for a formulary exception or coverage determination whereby you would continue to receive coverage for your existing medication.
Please remember that your Medicare Part D prescription drug plan may not automatically grant a request to cover a non-formulary medication and you may need to ask your doctor to get involved to support your request for an exception.
Also, if your request for a formulary exception is denied, you may wish to consider filing an appeal or a number of appeals to get your drugs covered for the remainder of the plan year.