H.R. 4881 — To amend title XVIII of the Social Security Act to limit cost sharing for drugs under the Medicare program.

This bill limits cost-sharing for covered drugs under the Medicare prescription drug benefit and Medicare Advantage. Specifically, for costs above the deductible but below the annual out-of-pocket threshold, the bill limits cost-sharing to the average net price of the drug (i.e., the average amount paid less any rebates) or the cash price (i.e., the price charged to an individual without insurance), whichever is lower.  The Government Accountability Office must report on the bill's implementation.