The most common objection to changing pharmacy benefit managers is timing. Sponsors worry that a mid-year move will interrupt members who are stable on their medications.
In practice, the things that matter most carry over. Active prior authorizations are reviewed and honoured, so a member already approved for a medication does not restart the process. Claims history transfers, which means medications someone has been filling consistently can often be pre-approved before they reach the counter.
What does change is the network and the formulary, and those are worth communicating early. A member whose pharmacy is leaving the network needs to know before their next refill, not at it.
The transition work is real, but it is largely administrative and it happens away from the member. The failure mode is not the data migration; it is the communication plan.