Pharmacy benefits costs account for more than 20% of total health plan costs at about 29% of employers that offer prescription benefits.

Researchers at Buck Consultants, New York, a unit of Affiliated Computer Services Inc., Dallas, have reported that finding in a summary of results from a survey of 150 employers.

Pharmacy benefits account for 16% to 20% of total health care costs at 37% of the participating employers, the Buck researchers report.

The researchers note that 99% of the participating employers said they offer prescription drug coverage.

The Buck researchers found signs that employers continue to have trouble understanding their pharmacy benefits costs.

About 28% of the participating employers did not know how much money their plans spend on expensive specialty medications, the researchers report.