European regulators on Friday took the rare step of extending the shelf life of a medicine for two years when they ruled that Tamiflu, the leading antiviral drug to treat flu, could be used for up to two years beyond its current expiry date.

The European Medicines Agency said for the first time ever that a medicine could remain safe to use for seven years, in response to concerns of a global shortage of a drug that could help prevent and treat a pandemic flu virus. “The recommendation is don’t throw it away,” said a spokeswoman.