"The recall is being expanded to include additional lots as a precautionary measure out of an abundance of caution", the drugmaker said in a statement Friday.
Pfizer Canada is recalling EpiPens because they may not work properly.
It says EpiPens distributed between January and March of a year ago and EpiPen Juniors from November 2015 to February 2016 were affected.
EpiPens are used to give an emergency injection of epinephrine to treat life-threatening allergic reactions. Meridian Medical Technologies manufactures the devices, which Mylan Specialty distributes in the United States.
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The widening recall is yet another setback for Mylan in its quest to maintain EpiPen as a big-selling product.
The auto-injectors may contain a faulty part in one lot of EpiPen and one lot of EpiPen Jr.
Mylan said in a release that the EpiPens that are recalled will be replaced at no cost.
If you have a recalled EpiPen, the FDA says don't toss it out until you get a replacement.
EpiPen (epinephrine) Auto‐Injectors are indicated for the emergency treatment of anaphylactic reactions in patients who are determined by a physician to be at increased risk for anaphylaxis.