The average Medicare Part D prescription drug plan rate may be going down in 2012, but 6 of the top 10 players in the market are raising prices.

Avalere Health L.L.C., Washington, a health policy firm, has analyzed Medicare drug coverage price changes in a commentary based on an in-house Medicare drug plan database and data from the Centers for Medicare & Medicaid Services (CMS).

CMS officials recently announced that overall Medicare drug coverage prices will be decreasing 4%.

But the Medicare drug plan operated by a unit of UnitedHealth Group Inc., Minnetonka, Minn. (NYSE:UNH), is the market leader, with 4.7 million enrollees, and that plan will be increasing premiums by an average of 14%, Avalere says.

The second largest plan will be increasing premiums 4%.

The Humana Walmart-Preferred Rx plan is the lowest-priced national Medicare drug plan, with average monthly premiums of $15.10, Avalere says.

The Humana-Walmart plan has a standard deductible of $320.

-Allison Bell

Other Medicare Part D prescription drug coverage from National Underwriter Life & Health: