One of the big reasons that expiration dates get set the way they do has to do with the approval process that the drug companies go thru to sell the drug. They have to prove that the drug is going to still be safe to take up thru the expiration date printed on the package that the product is shipped in to the pharmacies. To do this, a study must be conducted that requires a batch of the drug to be produced, then individual doses tested over time. Most companies don’t want the approval process delayed for 5 years so that they can put a 5 year expiration date on the drug even if the drug would still be effective at that time and will usually only run the study for 1 to 2 years.
The other part of this to think about is how long was the drug on the shelf at the pharmacy before it was dispensed into your pill bottle? If it is a little used drug, it could be close to the “expiration” date before it even gets into your hands. You will probably still get a 1 year date on the pill bottle in most cases. Would you still want to use the advice that you could use the pill upto a year after the expiration date?
I feel like I’ve spent the past 12 years answering this question, so because I just got off a plane and I’m tired and grumpy, I’ll simply suggest that people do a search on my username and the keyword “stability” - I’ve posted extensively about it as this question comes up about once a month on the boards.
Short version:
No one has tested it past a given date. There is no legal requirement to and no one will voluntarily spend the money to do so systematically if they don’t have to. No one knows what happens over time to most drugs because there is no data/information to examine to make any sort of determination… The risk of toxicity is one thing, but one of the larger risks is undermedicating (or overmedicating, if you try and compensate by taking extra doses) and the increased risk of side effects.
How many days past the Best Before on your milk would you drink it? A day? A week? A year? Milk is easy - you can see and smell when it’s gone off. Medicine is much harder to detect, but it will still go bad, eventually. Could be in a month after the expiration date, could be in a year, could be in a millennium. No one knows, no one will look into it, and even if the expiration date was moved to 5 years later, people would still be asking the same bloody question anyways.
The US military’s Shelf Life Extension Project doesn’t cover nearly the range and scope that most people wish that it did - it addresses particular lots of particular drugs but doesn’t even say anything whatsoever about the same drug made by a competitor. It provides a basis for more research, and a basis by which to assume that drugs are stable for longer than the label date (frankly, we already know that, given as the “expiry” is a guarantee of a certain potency value, not only a limit of allowable degradation), but it does NOT provide enough data or information to extrapolate to any and all drugs in any and all dosage forms stored and used under any and all circumstances. To suggest otherwise is just bad science, nevermind potentially very dangerous.
And that’s me saying that I didn’t feel like posting about it :smack:
Moderator Comment: Lunar Eclipse, welcome to the Straight Dope Message Boards, we’re glad you found us. Since there was already a thread on this topic, I have merged your thread into the already-existing thread. No problem, just keeps things neater.