Unfortunately I don't think there is any way to avoid the fluctuation in Part D Medicare co-pays - call your congressmen and senators, join AARP (they provide forms, online petitions, etc. to make it easy to let your legislators know your feelings). What you can avoid with a Medicare Advantage plan is only a separate Part D premium, not how Part D works. If you've ever heard reference made to the "donut hole" - that's what they are talking about!