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A growing chorus is calling on the Mylan pharmaceutical company to justify its price hikes on EpiPens, a potentially life-saving medication for children and others facing fatal allergies that has little real competition.

In 2007, a two-pack of the epinephrine-filled devices went for $56.64 wholesale, according to data gathered by Connecture, a health insurance technology and data analytics company. Now it's jumped to $365.16, an increase of 544.77 percent. Since the end of 2013, the price has gone up by 15 percent every other quarter.

EpiPen average wholesale price chart, 2007-2016. Ben Popken / NBC News

Doctors, parents, patients, and a former presidential candidate are speaking out on social media — and negative comments are filling up Mylan's Facebook page following an NBCNEWS.com story Wednesday.

And now, the Senator who allowed pushed for emergency epinephrine to be stocked in public schools has pledged to investigate the price increases.

At least one in 50 Americans has experienced anaphylaxis, a potentially life-threatening allergic reaction, according to a 2014 study published in the Journal of Allergy and Clinical Immunology.

"You are forcing many families to gamble with their children's lives, when your costs haven't gone up," wrote one Facebook post. Others questioned why the prices in the U.S. were higher than other countries for the same medicine.

"Amazing that Epipen prices in CA & EU with prescription are about $85. No govt negotiated buy in US," said another tweet.

Martin Shkreli, former CEO of Turing Pharmaceuticals LLC, prepares to testify before Congress on February 4, 2016. Joshua Roberts / Reuters

Even Martin Shkreli, the disgraced former chief executive of Turing Pharmaceuticals LLC, has weighed in.

"These guys are really vultures. What drives this company's moral compass?" he told NBC News in a phone interview.

In 2015, Shkreli famously jacked up the price of Turing's malaria and HIV medicine Darapim overnight, from $13.50 to $750, a move that earned him a grilling by the House Committee on Oversight and Government Reform in February — and the nickname "Pharma Bro" for his seemingly carefree attitude toward affordable medication.

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But Shkreli told NBC News he had originally considered gradually raising the price of Darapim, as Mylan did with the EpiPen. Ultimately, "the math, we felt, was a little silly; so we decided to come out and say 'This is our desired price.'"

The House committee doesn't currently have an open investigation into the price of EpiPens, MJ Henshaw, a spokesperson for the committee chair Representative Jason Chaffetz, said in an email.

In response to NBC's story earlier this week, Senator Bernie Sanders sent out a tweet questioning the price increase.

There's no reason an EpiPen, which costs Mylan just a few dollars to make, should cost families more than $600. https://t.co/rVWUlMxD0Q — Bernie Sanders (@SenSanders) August 18, 2016

There's a lawsuit in the works as well. Ari Kresch, CEO of 1-800-LAW-FIRM, said his firm was finalizing a filing against Mylan in the next couple of weeks.

"I've been looking at EpiPen for years," said Kresch. "It's a very cheap drug but I haven't been successful in getting any experts to tell me why the price has gone up as much as it has."

Mylan did not respond to phone or email messages seeking comment on the backlash.

In an earlier emailed statement, Mylan said its prices have "changed over time to better reflect important product features and the value the product provides," and that "we've made a significant investment to support the device over the past years."

The statement noted that commercially insured patients have successfully used its $100 coupon program, with nearly 80 percent of the My EpiPen Savings Card™ getting their auto-injectors for $0.

Two EpiPens used to treat severe allergic reactions with a dose of Epinephrine delivered in an autoinjector. John Makely / NBC News file

However, those without better insurance plans, or the uninsured, aren't able to take advantage of the program.

Dr. John Vann, a pediatrician in Omaha, Nebraska recalled the mother of a 14-year-old girl with walnut allergies crying in his office two weeks ago. She was on an HSA with a high deductible, and an EpiPen dual pack would have cost over $600. She didn't know how she would pay for it.

"You essentially have to have epinephrine around because if you have a reaction you need it," said Vann. "They hardly ever get used and it's a good thing — but if you don't have it, you're in trouble."

After doing some quick internet research, Vann was able to find "Adrenaclick," substitutable as a generic for EpiPen in 21 states, for just $200. The pharmacy was able to order it and have it available the next day.

Not all providers will cover it, though. He tried to do the same for another patient and the drugstore said that patient's insurance only pays for EpiPens.

"They did a pretty good job marketing themselves where it's just like Kleenex," said Vann. "People don't say 'epinephrine auto injector,' they say 'EpiPen.'"

Patients also expressed outrage in tweets and Facebook posts, and emails to NBC News.

Donna, a 52-year-old archaeozoologist from Hoover, Alabama who asked only her first name to be used, told how she felt her mouth, tongue, and eyes swelling shut after she was stung 26 times by yellow jackets on caving expedition a few years ago. That's when she learned for the first time that she was allergic. She hiked back several miles to her truck and sought treatment at the nearest hospital, two hours away.

"I barely survived and now have to carry two EpiPens at all times, even to the mailbox," she wrote in an email. "For Mylan to be the sole producer of this product and hold my life, and the millions of children and adult lives hostage for profit, is extortion and an outrage."

On Friday Connecticut Senator Richard Blumenthal said he would investigate the "shocking increase."

“As kids across the country head back to school, it is critical that their parents have affordable access to this life-saving product. I have heard from parents and first responders across Connecticut who are terrified that this steep price increase could put epinephrine out of reach for American families—and literally cost lives," said the Senator in a statement released to NBC News.

"Sadly, this case is just the latest in a greedy trend of skyrocketing prescription drug prices that are hurting consumers, limiting health options, and strangling our economy. I will investigate this shocking increase and continue doing everything I can in the Senate to combat the rising cost of prescription drugs across the board.”

Senator Blumenthal was the original cosponsor of the bill whose passage awarded grants to states that required public elementary and secondary schools to maintain emergency supplies of epinephrine and authorized school personnel to administer it to students experiencing an anaphylactic reaction.