Senator Jon Tester is fighting to hold a major pharmaceutical company accountable after it raised the price of its life-saving drug by more than 480 percent.

Since 2009, Mylan has raised the price of EpiPens in the United States from $103.50 a pair to $608.61 per pair, which has left numerous families unable to afford the life-saving drug.

“I am calling this what it is, Mylan is boosting their profits by holding families and sick children hostage with a life-saving drug,” Tester said after sending the letter.  “Folks deserve accountability for this shameful act that is leaving thousands in jeopardy, and I won’t stop exposing their actions until patients are able to once again purchase the medicine they need at an affordable and fair price.”

Currently Mylan has a near monopoly on the EpiPen and the company’s price increase has even forced emergency medical first responders to begin injecting patients with epinephrine using manual syringes—a less effective way of treating anaphylaxis.