People buying coverage on the nation's new health insurance exchanges last year used more medications than a comparison group with commercial insurance, according to a new report.

The finding fits with expectations that many of those who found coverage through the new marketplaces had unmet health care needs, said Michael Showalter, chief marketing officer at Eagan-based Prime Therapeutics, which released the report Wednesday.

There was a surprisingly high use of medications for hepatitis C and HIV among people on the exchanges, Showalter said in an interview. But he said the higher use doesn't necessarily signal a lasting financial problem for the new marketplaces.

"This report confirms our initial expectations that public exchange members would be, on average, older and have more health care needs than our commercially insured members," he said in a statement.

"I would expect over time that this is a bubble of sicker-than-average people," Showalter added in the interview, "and as they continue to have coverage they will start to look more and more like the average U.S. population."

Prime Therapeutics drew on data from nonprofit Blue Cross and Blue Shield insurance companies selling policies through exchanges in 14 states including Minnesota. The company last year managed pharmacy benefits for about 1 in 6 people across the country who purchased health insurance through a government-run insurance exchange.

Prime Therapeutics says it was the second-largest pharmacy benefit management company on the exchanges in 2014, behind St. Louis-based Express Scripts.

The study found the average age of those buying on the exchanges was 42.6 years, compared with 34.7 years among the broader commercially insured market.

People covered through the exchanges used an average of 11.7 prescriptions per year, compared to 10.3 prescriptions in the comparison group, for a 13.6 percent difference, the study found.

Average medication costs for those with exchange coverage were about $3 higher at $85.42 per member, per month.

Hepatitis C and HIV medications accounted for about 10 percent and 9 percent, respectively, of all medication costs for those covered through the exchanges, according to the report. In the comparison group, the drugs accounted for about 4 percent and 3 percent of spending for prescribed drugs.

"What was surprising to us was that two very small populations … would make up fully 19 percent of all the [spending] in our public exchange membership," Showalter said. "There was a huge unmet need, and people really needed coverage."

A new generation of hepatitis C medications offers patients a good chance at being cured at a cost of roughly $90,000 for a 90-day supply of medications. The cost of those drugs helps explain their outsized position among all medications used, Showalter said.

It's a different story, however, when it comes to treatment for the virus that causes AIDS.

"The story here is a whole bunch of people who weren't getting treated for HIV," Showalter said.

The study includes data from Blue Cross and Blue Shield of Minnesota, which had about 22 percent of the market during 2014 on Minnesota's MNsure exchange. Showalter said he could not comment on the extent to which the national trends shown in the report reflect the experience in Minnesota.

A spokesman for Golden Valley-based PreferredOne, which had the largest slice of the MNsure market during 2014, said that pharmacy cost and utilization was "significantly higher" with policies sold through the exchange.

The health law impact for people with HIV in Minnesota might be somewhat muted compared with elsewhere, because the state already offered subsidized access to coverage through a long-standing high-risk pool program, said Matt Toburen of the Minnesota AIDS Project. Even so, Toburen said: "We're seeing more people make that jump either into insurance for the first time, or back into insurance who have fallen out, because it's just more on the public radar."

The report looked at more than 13 million public exchange claims and more than 143 million commercial claims administered by Prime Therapeutics between Jan. 1, 2014 and Dec. 31, 2014. The company is owned by several Blue Cross insurance companies, and employs about 3,600 people.

Twitter: @chrissnowbeck