Enlarge (credit: Kaléo Pharmaceuticals )

Senator Patrick Leahy (D-Vt.) and thirty of his colleagues sent a letter to Kaléo Pharmaceuticals Wednesday to question the company’s price hike of its opioid-overdose-reversing device, Evzio.

As Ars has reported before, Evzio’s price rose dramatically over a short period of time—going from $690 in 2014 to $4,500 currently, according to the letter. Evzio is an easy-to-use auto-injector that delivers a dose of naloxone, a generic drug that blocks and reverses deadly opioid overdoses.

Amid the price increases, the country has been gripped by an epidemic of opioid addiction and overdoses. The CDC now estimates that 91 people die every day from an opioid overdose, and some hard-hit areas have even run out of morgue space.