Commercially insured patients forking over money out of pocket for brand-name medicines are paying based on the full list prices of those drugs, and cost sharing on nearly one out of five brand-name prescriptions is also based on list price.

That's according to new analysis from Amundsen Consulting, a division of QuintilesIMS, which found in spite of "robust negotiations between biopharmaceutical companies and payers," health plans don't pass along the savings achieved via rebates and discounts on the price of medicines, but instead still require patients with high deductibles or coinsurance to pay up based on the medications' full list price.

"While biopharmaceutical companies set the list prices for their medicines, it is the health plan that ultimately determines how much a patient pays out-of-pocket," Stephen J. Ubl, president and chief executive officer of the Pharmaceutical Research and Manufacturers of America (PhRMA), the organization that commissioned the analysis, says in a statement.