Don’t leave EpiPens in hot cars

Leaving an epinephrine autoinjector (EAI) in a hot car during a sunny day—even for a short time—can reduce epinephrine concentrations, according to the results of a small pilot study published in The Journal of Allergy and Clinical Immunology: In Practice. Alarmingly, these heated EAIs don’t change appearance (ie, no cloudiness, discoloration, or particles), so it’s impossible to tell visually that their concentrations have decreased following heat exposure.

“On the basis of our observations, we can hypothesize that even a single exposure to excessive heat in a car can decrease epinephrine concentration in an autoinjector below the recommended dosage,” wrote authors led by Piotr Lacwik, MD, Department of Internal Medicine, Asthma and Allergy, Medical University of Lodz, Lodz, Poland. “Although the decreases measured after this 1-day heat exposure would be unlikely to affect the effectiveness of the administered dose, further studies are needed to evaluate if such degradation is progressive or cumulative, which could lead to clinically ineffective underdosing.”

In this study, researchers placed three EAIs—one each in the trunk, cabin, and glove compartment of a parked black car—with no direct sunlight exposure—on a summer day when the ambient temperature ranged from 24°C to 32°C (75.2°F to 89.6°F). Furthermore, three EAIs served as controls and were stored in a dark, air-conditioned room at 20°C (68°F).

After 12 hours of exposure, the researchers utilized high-performance liquid chromatography (HPLC) to determine epinephrine concentrations in the EAIs. Of interest, only the EAIs taken from the glove compartment were warm to the touch, and none demonstrated changes in appearance, volume, or mechanism function.

Upon HPLC analyses, researchers noted a 3.3% decrease in epinephrine concentration in the trunk samples, a 13.3% decrease in the cabin samples, and a 14.33% decrease in the glove compartment samples. The greatest decrease in epinephrine concentrations occurred in the samples located in the glove compartment, which is where many people keep their first aid kits. The glove compartment stayed warm even after ambient temperatures dropped.

Little research has been done on the effect of extreme heat on epinephrine stability. Dr. Lacwik and colleagues cautioned about the effects of heat in their conclusion. “Epinephrine in low concentrations (eg, 0.1 mg/kg) can paradoxically produce vasodilation, hypotension, and increased release of inflammatory mediators, potentially worsening prognosis in anaphylaxis. Moreover, those observations may indicate the need for development of a new, heat-resistant storage solution or formulation, to delay epinephrine degradation in hot environments.”