Most US Medicare enrollees are unaware how much they will have to pay out of their own pockets if they are prescribed a "specialty tier" drug, a new study has revealed.

Specialty tiers are typically fourth-level formularies employed by insurance plans providing prescription drug cover (known as Part D) under the Medicare federal health programme for seniors and some disabled people. Specialty tiers include higher-cost, brand-name medications used to treat conditions such as cancer, multiple sclerosis, rheumatoid arthritis, HIV/AIDS and lupus.

The study found that many respondents were unaware that their Part D insurance plans charge differently for expensive medicines used to treat such complex, chronic diseases, with half of those surveyed believing that their plan would only require them to provide a co-pay rather than pay co-insurance for a drug on the specialty tier.

They also underestimated the amounts they would have to pay out-of-pocket for specialty-tier drugs, says the study, which was conducted by NERA Economic Consulting for Pfizer.

"While most respondents are aware that plans use tiered cost-sharing, a substantial percentage remains uninformed about the out-of-pocket costs associated with specialty-tier drugs," say the researchers. "These results suggest that, if confronted with having to take a drug on a specialty tier, many beneficiaries would be surprised to learn that they are responsible for a percentage of the cost rather than a flat co-pay."

"Furthermore, even those respondents who are aware that they would have to pay a percentage of the cost of a specialty-tier drug underestimate the amount they would have to pay," they add.

Meantime, a government study has found that Medicaid, the US federal/state health programme for people on low incomes, is paying considerably less than Medicare for prescription drugs. 

The report, by the Department of Health and Human Services' Inspector General, Daniel Levinson, found that rebates on 100 commonly-prescribed brand-name prescription drugs reduced their prices by 45% for Medicaid compared to just 19% for Medicare.