Q: I have several medications that are well beyond their expiration dates. Does that mean that they won't work -- or are dangerous?
A: The manufacturer's expiration date on most medications is 2-3 years from when the pills were made. This assumes they're still in their original container. When pharmacies repackage medications, they usually label them with a recommended-use date that's one year from when the prescription is filled. These dates serve more to protect the pharmacies and manufacturers than to tell you when your pills are no good.
The more important issue is whether pills lose their potency because they've been exposed to air, light, and moisture. If pills sit in their vials in a dry, dark place like a medicine cabinet, most will stay effective for at least five years. Some drugs have been shown to be stable as many as 30 years after they were made.
There are some important exceptions. Nitroglycerin loses its potency when exposed to light or moisture. This drug treats chest pain (angina) caused by coronary artery disease. I tell my patients to get new nitroglycerin tablets every 6-12 months, whether they think they'll need them or not. When you're having an angina attack, you don't want to put an old nitroglycerin pill under your tongue -- and not feel that comforting buzz that lets you know the medicine is doing its work.
Another thing to keep in mind: Drugs in liquid form are not nearly as stable as those in capsules or tablets. Take EpiPens, for example. These are auto-injectors for people having severe allergic (anaphylaxis) reactions. The potency of the epinephrine in an EpiPen tapers off within a year of the expiration date. That's another medicine you want to be sure is fresh in the event of an attack.
(Howard LeWine, M.D., is a practicing internist at Brigham and Women's Hospital, Boston, Mass., and Chief Medical Editor of Internet Publishing at Harvard Health Publications, Harvard Medical School.)
(For additional consumer health information, please visit http://www.health.harvard.edu.)