EpiPens – devices used to rescue people during a severe¬†allergic reaction¬†— can remain effective years after their expiration date, a new study reports.

An evaluation of almost 40 expired, unused EpiPens brought in by patients revealed that all of the devices contained more than 80 percent of their initial dose of epinephrine. This was true even as long as four years past the expiration date on the device, said study lead researcher F. Lee Cantrell, director of the California Poison Control System – San Diego Division.

Cantrell FL, Cantrell P, Wen A, Gerona R. Epinephrine Concentrations in EpiPens After the Expiration Date. Ann Intern Med. [Epub ahead of print 9 May 2017] doi: 10.7326/L16-0612