Epinephrine might still have its life-saving potential even if it freezes and thaws out while you’re backpacking in the dead of winter, an experimental study finds.
“It’s definitely a small study, but it gives us pretty conclusive evidence that the freeze-thaw does not seem to degrade the epinephrine,” said Dr. William Smith, an emergency medicine physician at St. John’s Medical Center in Jackson Hole, Wyoming, and one of the study’s authors. “If it does freeze, it’s most likely going to be okay to administer and help the patient in an emergency setting.”
Epinephrine is used by people with severe allergies to insect stings, plants, medications or certain foods, the authors note in the journal Wilderness and Environmental Medicine. An estimated 1 to 2 percent of the population worldwide has such life-threatening allergies, they write.
Without the life-saving drug, those people can experience itchiness and swelling, shortness of breath or even heart attack and death when exposed to an allergen.
People who know they’re at risk usually carry the epinephrine in autoinjectors, such as EpiPen, which offer a single-use dose of 0.3 mg of the drug intramuscularly by needle and syringe.
“It’s all the way from people in ski areas to backpackers to mountain climbers and guides, as well as people carrying with a history of severe allergic reaction or anaphylaxis and not even having a medical degree…,” said Smith, also a paramedic and medical director with the U.S. National Park Service.
In backcountry conditions, Smith and colleagues write, the medication may be exposed to extreme temperatures. The EpiPen’s instructions include a recommendation to replace the device if it has been accidentally refrigerated, but the researchers wanted to see if the product might still be useful in an emergency.
The study team measured the concentration of epinephrine in the standard dose from an autoinjector, then froze and thawed the liquid multiple times over seven days, measuring the epinephrine concentration after each thaw.
The samples subjected to freezing were brought to minus-25 degrees celsius (minus-13 degrees Fahrenheit) and then allowed to warm to room temperature, about 22 degrees C (73 degrees F). These samples were also compared to doses in sealed glass vials that remained at room temperature but away from direct sunlight during the same cycle.
After seven days of freeze-thaw cycles, the experimental samples had a concentration of 1.041 to 1.106 milligrams of epinephrine per milliliter of fluid, falling within the 0.90 to 1.15 mg/mL considered safe by United States Pharmacopeia standards.
“We would have expected the amount of epinephrine in our samples to change after multiple freeze-thaw cycles if degradation of the molecule had been occurring, but actually our results showed that epinephrine concentration generally went up in a statistically significant trend,” said the study’s lead author Heather Beasley, a medical student at the University of Utah School of Medicine, by email.
The authors said a loss of solution or an error could have led to the slight increase in epinephrine concentrations in the frozen samples and more study is needed.
Dr. Venkatesh Ballamkonda, a director in the emergency medicine department at Mayo Clinic in Minneapolis, Minnesota, called the experiment intriguing.
“Many times medical literature doesn’t have easy applicability to real life and here’s one that goes from the basic science arena to real world applicability very easily all the way down to the child going to school with a peanut allergy,” Bellamkonda told Reuters Health.
“If it were your son or my son or daughter, I’d want to know the epinephrine is still good to use if it sits outside,” he said.
Bellamkonda, who was not involved in the study, also noted that a larger study should examine epinephrine in autoinjectors and not just vials to gauge how well the devices protect the medication.
“Certainly it’s not conclusive in any way but I think it highlights an interesting opportunity for (more) knowledge,” Bellamkonda said.