Two senior lawmakers on the U.S. Senate's Judiciary Committee pushed for information regarding sharp price increases for EpiPens, drug-filled injectable devices used by people to counter potentially deadly allergic reactions.

Senator Chuck Grassley, chairman of the Senate Judiciary Committee, wrote Mylan Chief Executive Heather Bresch on Monday to ask how Mylan determined the price of EpiPens and what changes had been made to the product to account for the higher price.

The top Democrat on the committee's antitrust subcommittee, Senator Amy Klobuchar, urged the Federal Trade Commission on Monday to investigate the prices, citing news reports showing that the price of a pack of two EpiPens had gone from $100 in 2008 to $500 this year. Mylan acquired the product in 2007.

"Although the antitrust laws do not prohibit price gouging, regardless of how unseemly it may be, they do prohibit the use of unreasonable restraints of trade to facilitate or protect a price increase," wrote Klobuchar, a Minnesota Democrat who said her daughter relies on an EpiPen.

"The FTC should investigate whether Mylan Pharmaceuticals engaged in activity, such as using incentives or exclusionary contracts with insurers, distributors, or pharmacies, to deny an alternative product access to the market."

An EpiPen injects a pre-measured dose of epinephrine (adrenaline) that people use if they are having a dangerous allergic reaction.

The FTC did not say whether an investigation was under way. "The commission takes seriously its obligation to take action where pharmaceutical companies have violated the antitrust laws," a spokesman said.

Mylan did not immediately comment on the letters but noted in an email that nearly 80 percent of people with commercial insurance who use a savings card can get the medicine for free.

"With changes in the healthcare insurance landscape, an increasing number of people and families are enrolled in high deductible health plans, and deductible amounts continue to rise. This shift has presented new challenges for consumers, and they are bearing more of the cost," Mylan also said.

The FTC opened a probe into Turing Pharmaceuticals for possible antitrust violations in connection with the company's decision to sharply raise the price of a life-saving drug. Turing had raised the price of Daraprim to $750 a tablet from $13.50.