WASHINGTON (Reuters) - Democrat Elizabeth Warren and 19 other U.S. senators voiced concern to the chief executive of Mylan NV (MYL.O) about the high cost of its EpiPen on Tuesday, calling the device used in the case of life-threatening allergies “exorbitantly expensive.” Mylan has been under fire for steadily raising the price of the device from about $100 in 2008 to about $600 currently. In a letter to Mylan CEO Heather Bresch, the daughter of Senator Joe Manchin of West Virginia, the lawmakers asked the company to spell out the company’s programs to provide some people with lower cost EpiPens. Such discount programs are often an “industry tactic to keep costs high through a complex shell game,” the letter said. “Insurance companies, the government and employers still bear the burden of these excessive prices. In turn, those costs are eventually passed on to consumers in the form of higher premiums,” the senators wrote. Mylan said this week it would launch the first generic version of its allergy auto-injector EpiPen for $300, half the price of the branded product, the drugmaker’s second step in less than a week to counter the backlash over the product’s steep price. It also reduced the out-of-pocket costs of EpiPen for some patients last week. EpiPen has a 94 percent market share for auto-injector devices, which jab a dose of the drug epinephrine into the thigh to counter dangerous allergic reactions such as to peanuts, other foods and bee stings. Asked about the letter, Mylan spokeswoman Lauren Kashtan said in an email statement: “We have acknowledged receipt of letters from congressional offices and intend to respond to them.” Mylan has defended EpiPen’s high price, saying it spent hundreds of millions of dollars to improve the product since acquiring it in 2007. It has also said it recoups less than half the list price for EpiPens. In their letter, the lawmakers asked Mylan how much insurers paid for the EpiPen in 2009 and how much they pay now. They also asked how many EpiPens Mylan provided to low income, uninsured consumers and how many schools purchased EpiPens versus how many received them for free. In addition to Warren, other signatories included Senators Patrick Leahy of Vermont, the top Democrat on the Judiciary Committee; Barbara Boxer, a California Democrat; Dick Durbin, an Illinois Democrat; Jack Reed and Sheldon Whitehouse, both Democrats from Rhode Island and Sherrod Brown, an Ohio Democrat. 