The prescription drugs that have seen the most rapid growth in cost in the U.S. don't treat depression, cholesterol or even autoimmune diseases.

Blockbuster male libido treatments Viagra and Cialis saw the biggest price hikes among the 17 top-selling brand-name drugs that have seen costs surges from 2012 through 2017, according to a new study published Friday in the peer-reviewed Journal of the American Medical Association.

Researchers from the Scripps Research Translational Institute analyzed six years of pharmacy claims data from the Blue Cross Blue Shield Axis, a database of more than 35 million individuals with private prescription drug insurance. They found there was a "near universal" increase in net prices of 49 brand-name drugs with 17 of those drugs seeing prices double over the time period.

The largest price increase came from Pfizer's Viagra, which surged by 190% over the six-year time period to $370 from $127 per prescription, according to the study. That was followed by Viagra rival Cialis, produced by Eli Lily, which rose by 187% to $365 from $127 for a prescription. Eli Lilly's osteoporosis drug Forteo came in third with a 177% price increase.

Nathan Wineinger, an assistant professor at Scripps Research and lead author of the study, said researchers didn't see any difference in cost increases between drugs that had been on the market for a significant period of time, were relatively new or a had a generic version. That "was disheartening," he said.