As you’re probably all too aware, the U.S. is in the midst of an opioid epidemic, meaning that some life-saving overdose treatments have become crucial tools for hospitals, law enforcement, first responders, and families of addicts. At the same time, the makers of one such vital drug have raised the price by more than 600% since 2014, drawing the attention of lawmakers who want to know why.

This morning, 31 U.S. Senators sent a letter [PDF] to the CEO of Virginia-based Kaléo Pharmaceuticals, seeking information on the soaring price of the company’s Evzio (naloxone) injectors.

Since 2014, the cost of twin pack of Evzio has jumped from $690 to $4,500 without any apparent reason for such a dramatic change in cost.

“This drug is now in the hands of first responders and families struggling with substance use disorder across the country,” reads the letter, noting that more than 30,000 Americans die each year from opioid overdose. “It is particularly needed in rural areas where access to life-saving emergency services can be limited. Such a steep rise in the cost of this drug threatens to price-out families and communities that depend on naloxone to save lives.”

Though intravenous, generic naloxone is significantly more affordable than Evzio, it is not as easy to use for a layperson as an auto-injector like Evzio. So the choice is between having access to the treatment but not being sure you’ll be able to administer it properly when the time comes, or having a user-friendly version of the drug that most people can’t afford.

This is very similar to the dilemma that thrust emergency allergy treatment EpiPen into the spotlight last year. One could — as some first responders did — purchase epinephrine and needles for very little money, but that’s not the same as having an auto-injector that virtually anyone can administer.

“Evzio was designed to be simple to administer, making it particularly well suited for use by laypersons such as families looking to protect loved ones from overdose,” write the lawmakers. “Unfortunately, reports indicate Kaléo has responded to the increased need for naloxone devices by ratcheting up the price for Evzio.”

The letter notes that Kaléo has downplayed concerns about the $4,500 price, noting that this is a list price and not a “true gauge” of what consumers are actually paying, and that in reality many users are getting Evzio for little or no out-of-pocket money.

Nevertheless, the senators say they remain “concerned about the impact the high list price may have for those who do not qualify for the program and for state and local entities who hope to purchase large quantities of your product.”

To that end, the letter asks for more detailed information on the company’s reasons for raising the price of Evzio, including information about any changes in the cost of production.

Just as with EpiPen, there are programs to provide Evzio to certain groups at no or minimal cost, so the lawmakers want to know exactly how many devices Kaléo sets aside for these programs, and what the company does to inform consumers of their eligibility.

Some critics have likened such programs to free samples, intended to primarily raise brand awareness in guise of public service.

Finally, the senators want to know just how much revenue Kaléo has earned from purchases made by the federal government in the last year. There’s also the issue of how much federal money has been spent indirectly on Evzio through third parties that use federal funds to purchase the injectors.

The letter was signed by Sens. Patrick Leahy (VT), Al Franken (MN), Christopher Murphy (CT), Jack Reed (RI), Dick Durbin (IL), Sheldon Whitehouse (RI), Maria Cantwell (WA), Dianne Feinstein (CA), Tammy Baldwin (WI), Claire McCaskill (MO), Jeanne Shaheen (NH), Angus King (ME), Richard Blumenthal (CT), Edward J. Markey (MA), Maggie Hassan (NH), Amy Klobuchar (MN), Heidi Heitkamp (ND), Elizabeth Warren (MA), Tammy Duckworth (IL), Kirsten Gillibrand (NY), Joe Donnelly (IN), Jon Tester (MT), Bernie Sanders (VT), Sherrod Brown (OH), Debbie Stabenow (MI), Tom Udall (NM), Tim Kaine (VA), Mark Warner (VA), Gary Peters (MI), Jeff Merkley (OR), and Cory Booker (NJ).

UPDATE: In a statement emailed to Consumerist, Spencer Williamson, CEO of kaléo said the following:

“We received the letter from the Senators and are in communication with them to ensure all questions are addressed. Our first priority remains ensuring that patients can access EVZIO. In fact, with the launch of kaléo’s enhanced patient access program, more Americans are able to obtain this life-saving product for $0 out-of-pocket than any time in history.

“Details of how we are ensuring the broadest access to EVZIO for patients and their loved ones through our patient access program include:

· For the more than 200 million Americans with commercial insurance and a prescription, they can get EVZIO for $0 out-of-pocket.

· For patients who do not have government or commercial insurance, and have a household income of less than $100,000, they can also receive EVZIO for $0 out-of-pocket.

· For those paying cash, the price is $360.

“As the senators noted, EVZIO was designed for use by those without medical training, as most life-threatening opioid emergencies occur in the home and are witnessed by friends or family who may be in the best position to intervene quickly with naloxone. Through quick administration of EVZIO by caregivers, we can help save lives while saving significant costs to the healthcare system by avoiding long term in-patient care. No naloxone product, branded or even generic, is less expensive for commercially insured patients, or patients without insurance and incomes below $100,000 a year, than EVZIO.

“Since EVZIO was not designed for the bulk purchase market, which is comprised primarily of first responder agencies, health departments and harm reduction organizations, we developed the kaléo Cares Product Donation program to provide EVZIO free of charge and ensure communities in need can access our product. To date, we have donated nearly 200,000 doses of EVZIO and it has been reported to us that 2,800 lives have been saved through this program.

“Our goal at kaléo is to ensure the broadest access possible to this potentially life-saving medication.”

Editor's Note: This article originally appeared on Consumerist.