The Medicare Part D rebate rule finalized by the Trump administration last November could be in limbo for a while. As it did with other so-called midnight rules issued in the waning days of the Trump presidency, the U.S. Department of Health and Human Services, under the Biden administration, is postponing the implementation of the rule, which was intended to simplify the U.S. drug pricing system by eliminating the rebates drug makers pay to pharmacy benefit managers for formulary placement or requiring plans to pass the discounts directly to patients.