EpiPen was added to the FDA's drug shortage list in May.
"We are doing everything we can to help mitigate shortages of these products, especially ahead of the back-to-school season," Dr. Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research, said in a statement. "We've completed the necessary reviews of the data to extend the expiration date by four months for specific lots of EpiPen that are expired or close to expiring. We're hopeful this action will ensure patients have access to this important medication and provide additional peace-of-mind to parents as the agency works with the manufacturer to increase supply."
The extension applies to EpiPen products that have expiration dates between April and December of 2018, according to Pfizer.
EpiPen users who have pens within that expiration date window can now use the drug four months past the 20-month expiration date, according to the FDA.
It applies to specific lots of EpiPen 0.3-milligram auto-injectors and authorized generic EpiPens marketed by Mylan.
Last week, the FDA announced it approved the first generic version of EpiPen, which will be available in the coming months.