Background: EpiPen and EpiPen Jr autoinjectors are often recommended for prehospital treatment of anaphylaxis. When these units become outdated, there may be a delay in replacing them.
Objectives: Our purpose was to evaluate unused, outdated EpiPen and EpiPen Jr autoinjectors, obtained from patients at risk for anaphylaxis, for epinephrine bioavailability and epinephrine content.
Methods: We conducted a prospective, randomized, cross-over study of epinephrine bioavailability after injection from outdated autoinjectors in rabbits; controls included EpiPen and EpiPen Jr autoinjectors that had not expired ("in-date" autoinjectors) and intramuscular injection of 0.9% saline solution. In addition, the epinephrine content of the outdated EpiPen and EpiPen Jr autoinjectors was measured by a spectrophotometric method and an HPLC-UV method.
Results: Twenty-eight EpiPen and 6EpiPen Jr autoinjectors were studied 1 to 90 months after the stated expiration date. Most were not discolored and did not contain precipitates. Epinephrine bioavailability from the outdated EpiPen autoinjectors was significantly reduced (P <.05) compared with epinephrine bioavailability from the in-date autoinjectors. The inverse correlation between the decreased epinephrine content of the outdated autoinjectors, assessed with an HPLC-UV method, and the number of months past the expiration date was 0.63.
Conclusions: For prehospital treatment of anaphylaxis, we recommend the use of EpiPen and EpiPen Jr autoinjectors that are not outdated. If, however, the only autoinjector available is an outdated one, it could be used as long as no discoloration or precipitates are apparent because the potential benefit of using it is greater than the potential risk of a suboptimal epinephrine dose or of no epinephrine treatment at all.