Heather Bresch, chief executive of Mylan, holds up EpiPen medication while speaking at a House Oversight and Government Reform Committee on Sept. 15. (Andrew Harrer/Bloomberg News)

Mylan chief executive Heather Bresch said one thing at a contentious hearing last week that should be music to the ears of people with life-threatening allergies: Her company will soon push to extend the shelf life for EpiPen.

Currently, EpiPens expire 18 months from date of manufacturing. Facing criticism for the drug's rapidly rising price, Bresch said the company hopes the expiration date can be extended to a minimum of 24 months.

To make the case, Mylan will need to convince regulators that their data demonstrates that a new EpiPen formulation can remain effective for months longer.

"We hope, within the next 12 months, we will have approved a new formulation that will extend the shelf life," Bresch said during Thursday's hearing.

An extension would increase the time between refills and help quell a common complaint among patients and parents who have to toss out unused EpiPens annually and buy new ones. There's a common misconception that EpiPen's shelf-life is just a year, because time elapses between the manufacturing of the drug and when people pick up their prescriptions.

This wouldn't be the first time EpiPen's expiration date was altered. In 2002, the shelf life was 27 months, but a formulation change by the then-owner Meridian Medical Technologies required a shorter expiration date, said Theresa Eisenman, a spokeswoman for the Food and Drug Administration. Initially, the approval was for 20 months, but subsequent data supported 19 months. The company decided to use 18 months, she said.

EpiPens are, fortunately, needed only in emergencies. Discarding them unused on a regular basis can feel wasteful, particularly when the price tag has gone up to more than $600 for a pack of two -- but it's also critical that they work, exactly as designed, when they are needed. Doctors say questions about the expiration date of the product come up all the time.

The origins of EpiPen's expiration date

EpiPen's shelf life has been limited by the chemistry of the drug inside it. Epinephrine is an old and cheap medication, but it's also notoriously finicky. If exposed to light, heat or air, it can degrade, turning rust colored.

The FDA-approved label warns that if the liquid in the pen is discolored, it should be discarded: "Epinephrine solution deteriorates rapidly on exposure to air or light, turning pink from oxidation to adrenochrome and brown from the formation of melanin."

But what about an expired EpiPen that looks perfectly normal?

The little published data that exists shows that the drug degrades over time -- and color is not an accurate way to gauge whether the epinephrine inside is still good.

One study, published in the Journal of Allergy and Clinical Immunology in 2000, examined EpiPens one to 90 months after the expiration date. Most were not discolored, but the epinephrine content decreased over time. The study stated that it was best to use EpiPens that had not expired, but found that the pens contained at least two-thirds of the intended dose up to a year after expiration. Even a sub-optimal dose could be better than nothing in a life-or-death situation, the authors concluded.

Another study, published in the Annals of Allergy, Asthma and Immunology in 2015, found that EpiPens contained more than 90 percent of the labeled dose for up to two years after the expiration date.  The study also found that the color did not reliably indicate whether the epinephrine had degraded.

Eisenman said that because of "concerns about the ability to extend its shelf life," EpiPen is not in the federal shelf-life extension program, a federal program designed to aid in stockpiling drugs for public health emergencies. The program allows for the shelf life of stockpiled drugs to be extended after products undergo stability testing.

"In 2012, FDA’s Office of Testing and Research examined several EpiPen samples that were beyond their expiration date and the data raised concerns," Eisenman said in an e-mail. The agency found an indicator that the drug had decreased in potency and "concerns about discoloration, which indicates degradation is likely occurring."

What happens when an EpiPen expires?

Medical professionals say that they would always recommend patients carry in-date EpiPens, but that if an expired EpiPen is all that is on hand in an emergency, people should use it.

Data suggests the drug can remain useful after the expiration date -- "with a predictable, slow decline over time," Julie Brown, an emergency medicine physician at the University of Washington's health care system, said in an email.

In one case reported by ABC News in 2013, a mother who had only an expired EpiPen on hand when her teenage son went into anaphylactic shock was instructed not to use it by first responders. A neighbor brought over an EpiPen, but the young man died. It was unclear whether the out-of-date pen would have saved his life, according to the news report.

"The effect of degradation products of epinephrine on health is unknown, but when you are talking about a life-threatening reaction and no alternative options, you are weighing that unknown and likely small risk against the greater risk of not treating the life-threatening reaction," Brown said. "Not using an available device, even an expired one, likely places someone in anaphylaxis at greater risk than using it."

Wayne Shreffler, chief of pediatric allergy and immunology at Massachusetts General Hospital, said in an email that parents ask questions about expired EpiPens all the time.

"In the absence of data I'm confident in, I recommend that people replace their devices when they're expired, but say use if you have nothing else," Shreffler wrote.

Mylan isn't the only company working on the problem. Chris Stepanian runs a startup called Windgap Medical, based in Somerville, Mass., which is focused on creating an epinephrine autoinjector that is more compact, resistant to temperature extremes and long-lasting than the EpiPen. His tiny company is still in a very early stage -- it won't submit an application to regulators until 2018 -- but he said that it was not trivial to prove that a product can be safe and effective for a very long time.

"If you want a very long shelf life, say five years, you're probably going to have to test it for five years before you can submit," Stepanian said.

More from Wonkblog: