Effects of an out-of-pocket maximum in Medicare Part D

Three different out-of-pocket (OOP) maximums in Medicare Part D have been proposed: $2000 by the House of Representatives, $3100 by the Senate Finance Committee, and the beginning of catastrophic coverage by the Medicare Payment Advisory Commission. However, little is known about how beneficiaries would be affected.

We estimated multivariate linear regression models to determine which beneficiary characteristics were associated with the greatest savings under each proposed OOP maximum and simulated a potential behavioral response by beneficiaries.

Using Part D 2017 claims data for beneficiaries in stand-alone prescription drug plans (PDPs) and Medicare Advantage prescription drug (MA-PD) plans, we estimated the number of beneficiaries affected, their demographic characteristics, and their drug utilization patterns. We then simulated a potential behavioral response by beneficiaries.

Under the $2000 OOP proposed threshold, only 7% of PDP and 4% of MA-PD plan beneficiaries would have spending high enough to reach the OOP maximum. Annual mean (SD) savings would be $1301 ($1849) for PDP beneficiaries and $1363 ($1888) for MA-PD plan beneficiaries, concentrated among beneficiaries taking specialty drugs. As the threshold increases, fewer beneficiaries would accrue savings, but savings would increase. For the highest proposed OOP maximum, mean (SD) savings would be $2720 ($3465) and $2473 ($2805) for PDP and MA-PD plan beneficiaries, respectively. In our simulations, we estimated that the number of beneficiaries affected by an OOP maximum could increase by 2% to 11%, depending on the magnitude of response, but changes in savings would be minimal.

As currently drafted, proposed OOP maximums would reduce OOP spending for a small population of Part D beneficiaries, with savings concentrated among beneficiaries with the very highest costs who are taking specialty medications.