NEW YORK -- The FDA issued a warning to patients about the EpiPen on Tuesday.
In a news release, FDA said EpiPen manufacturers Pfizer and Mylan sent a letter to health care providers noting the EpiPen may not work properly due to spontaneous activation and users may have trouble taking it out of its packaging.
The EpiPen, an injection of the hormone epinephrine, is used as an emergency treatment for severe allergic reactions.
Pfizer and Mylan said some EpiPens are activating before patients can receive the injection, which means that device can't be used anymore and the patient would have to get a new EpiPen.
The letter said because the EpiPen treats potentially life-threatening reactions, anything that prevents the immediate administration of the drug could put the patient at high-risk of severe complications, including death.
The manufacturers warned of two potential reasons the device may activate spontaneously: if a patient tries to hold the pen sideways in one hand and take off the safety release with their thumb rather than holding it straight up and taking off the release with their other hand, or if the safety release is already slightly raised before the patient tries to use the injector.
In addition, the manufacturers said some EpiPens may not come out of their carrier case easily because the plastic tube may be slightly warped. While Pfizer said this issue is very rare, it could affect any injector currently on the market in the U.S. with an expiration date before September 2020.
Pfizer and Mylan also detailed several potential user errors, such as not removing the safety release, not injecting the EpiPen into the outer thigh or not holding the injector in place for a full three seconds.
"It is vital for lifesaving products to work as designed in an emergency situation, and patients and caregivers should inspect their epinephrine auto-injector prior to needing it to ensure the blue safety release is not raised and that the device can be easily removed from the carrier tube," the FDA wrote in its statement.
Anyone who finds an issue with their EpiPen should contact Mylan Customer Relations at 800-796-9526 to get a free replacement.
FDA warns patients EpiPens may malfunction, delay injections