This is according to a new study in the Archives of Internal Medicine.
Doctors looked at eight prescription drugs which expired 28 to 40 years ago. They found most remained just as potent as the day they were made.
For the majority of the drugs tested, at least 90 percent of the active ingredient was still within the acceptable range for the Food and Drug Administration.
Researchers stress the expiration date only means the manufacturer is willing to guarantee the potency of the drug through that date, but there is no way to know if the shelf life of the pills will be longer.