About a year ago, Martin Shkreli's Turing Pharmaceuticals bought a drug and then increased its price 5,000%, raising awareness about how the cost of a drug can skyrocket virtually overnight, especially when it doesn't face much generic competition.

Today, drug prices are still going up across the board. Case in point: the EpiPen.

In 2007, when drugmaker Mylan bought the autoinjecting device, which contains epinephrine (otherwise known as adrenaline), the list price was $57. Now, a two-pack EpiPen will set you back more than $600 without insurance, according to prescription-drug price comparison website GoodRx. Since 2009, when it was $100 for a pack of two, the price has gone up about 500% (though the price varies among pharmacies). And senators are starting to ask for answers.

The price increases have helped transform the EpiPen into a billion-dollar business despite it being a decades-old product.

Meanwhile, according to Consumer Reports, some desperate patients who can't afford EpiPens anymore have turned to filling syringes with epinephrine themselves — an extremely tricky and potentially dangerous alternative.

Why the EpiPen doesn't have much competition

The EpiPen has competitors, though one, called Auvi-Q, has been recalled since last October. The other, called Adrenaclick, is a little different to use (it uses two caps instead of one, for example) and costs more than $400 without insurance, according to GoodRx (though significantly cheaper options may be available with coupons).

A generic version of the EpiPen did not get approval from the Food and Drug Administration; the agency cited "certain major deficiencies."

These devices are used in emergencies to treat anaphylaxis, a severe allergic reaction that can make people go into shock, struggle to breathe, or get a skin rash. It's a common symptom of severe allergies, with one report saying about one in 50 people in the US could be at risk.

And these medications, which are kept on hand in case of a reaction, expire after a year, which means people have to stay up to date with new prescriptions even if they haven't used a past one.

In its second-quarter earnings, reported August 9, Mylan attributed its increased sales for specialty drugs (up 33% over 2015) to "higher unit volumes and the realization of the benefits of customer contract negotiations over the last several quarters related to the EpiPen Auto-Injector," combined with higher sales for some of its other specialty products.

In response to questions about its high list price, Mylan noted in an email to Business Insider that about 80% of people with commercial insurance who also used a "My EpiPen Savings Card" received the device for $0.

"With changes in the healthcare insurance landscape, an increasing number of people and families are enrolled in high-deductible health plans, and deductible amounts continue to rise," Mylan said. "This shift has presented new challenges for consumers, and they are bearing more of the cost. This change to the industry is not an easy challenge to address, but we recognize the need and are committed to working with customers and payors to find solutions to meet the needs of the patients and families we serve."

With the new school year starting, people are losing patience

Senators are starting to ask questions

Politicians, including Sens. Bernie Sanders, an Independent from Vermont, and Amy Klobuchar, a Democrat from Minnesota, are weighing in on the issue as well.

On Saturday, Klobuchar called for a Senate Judiciary Committee hearing to investigate the price increase. Sen. Chuck Grassley, a Republican from Iowa, on Monday asked for more information regarding the cost, as well as Sen. Richard Blumenthal of Connecticut, who penned a letter and gave Mylan until Sept. 5 to respond.