Members of Congress are demanding more information on why the price for lifesaving EpiPens has skyrocketed.

EpiPens are injection devices used to ward off potentially fatal allergic reactions and the price has surged in recent years. A two-dose package cost around $94 nine years ago. The average cost was more than six times that in May, according to the Elsevier Clinical Solutions’ Gold Standard Drug Database.

Sen. Charles Grassley (R-Iowa) wrote Mylan, the company that manufactures the devices, and asked for more information on why the prices have increased. He cited the cost to parents whose children need them and also to schools that keep the EpiPens on hand. He noted the costs can also be passed on to taxpayers when children are covered by Medicaid or other government programs.

“As the parent of a child with severe allergies, I am all too familiar with the life-or-death importance of these devices,” Sen. Mark Warner (D-Va.) wrote. 

A two-dose package sold for an average $608 in May, according to the Elsevier database, and has possibly risen since then.

The price is especially burdensome for uninsured families or those on health plans with high deductibles. 

In a statement issued Monday, Mylan said it has savings programs for patients and is also offering free EpiPens to schools. The company said around half of U.S. schools are participating in that program.

Recent changes in health insurance have resulted in higher deductible costs for many families, the company said. “This current and ongoing shift has presented new challenges for consumers, and now they are bearing more of the cost” of the devices, the statement said.