Medicare Part D drug plan enrollees usually pay considerably less for prescription drugs than posted carrier drug prices indicate.

Officials with the inspector general’s office at the U.S. Department of Health and Human Services have come to that conclusion in a review of the accuracy of a Part D plan drug price database.

The officials based their analysis on a review of prices for 10 commonly used drugs that were fed into the Part D program “Plan Finder” system from Sept. 24, 2007, to Oct. 7, 2007.

The Plan Finder drug prices were 28% lower than the actual drug prices, officials report. For 19% of the claims, Plan Finder prices were more than 100% higher than the actual drug costs.

Plan Finder prices were less than the actual drug prices only 7% of the time.

HHS inspector general’s office officials are recommending that the Part D program regulators improve the accuracy of the Plan Finder database by doing more to compare the Plan Finder costs with actual claims. In the short run, inspector’s general office officals write, regulators should include a disclaimer with the Plan Finder search results warning that drug cost estimates may differ more than slightly from the actual costs.

A copy of the HHS inspector general’s office review is available here.