Things fall apart, the center cannot hold. I understand that. Even fairly stable molecules will shake themselves to pieces, given enough time. So it makes perfect sense for just about anything to come with an expiration date… including prescription drugs.
But I find it an incredible coincidence that just about every drug I’ve ever purchased from a pharmacy has an expiration date exactly one year after the day the prescription was filled. And I mean “incredible” literally; I don’t buy it, it lacks credibility. Different compounds will decay at different rates, and presumably the pharmacist lacks a stasis chamber and so expiration ought to be dependent on when the drug was manufactured, not when the prescription was filled.
Oh, I’m sure the rationale is “better safe than sorry”, and has nothing whatsoever to do with the desire of pharmacists to sell more drugs. But suppose I feel like taking a gamble, and decide that the reward of not throwing away perfectly good medication justifies some degree of risk. Where and how can I find out how long my drugs will really remain safe and effective?
I did a Google on “expiration dates on medications” and the very first page gave me these three sites, all of which say that meds are fine even years past the expiration date: Harvard Medical School Johns Hopkins WebMD
IAAPS (Pharmacy Student), and I actually answered this question yesterday in this thread. Here is what I said on this particular subject:
One thing to remember about those studies on old drugs, they are testing the drug after it has been in controlled storage, not after it’s been in your medicine cabinet where it experiences high humidity and variable temperatures.
The expiration date is 1 year on most drugs, because that is how long they run the tests on them to prove them effective. They store the drug for a year (under proper conditions, as mentioned) and then test it to see if it still works.
They don’t test longer than that because:
it delays getting the drug onto the market, costing them money.
there is no significant increased sales from a longer expiration date (probably costs sales!).
t-bonham@scc.net, not quite. When they are first developing new drugs (i.e. during the clinical trials), they do what is called Advanced Stability Testing. This is where they increase the temperature and other environmental cues so that it acts as it would if it was aged. They use this to see how long the medication is stable under normal storage conditions (aka, USP [United States Pharmacopoeia]). However, this is only good for a maximum for three years, any longer and they would have to test an actual bottle of the medication. Since it is in trials, and since it would be approved before the three years is up, normally they just go with the AST results.
The one year after repackaging has to due with what I said before. Mainly, they can’t guarantee the way something is stored.
The thing is, it all depends. If it’s hot, with high humidity and the bottle’s been opened (of course if it’s a prescription, you nearly always have the pills from an unsealed container) they don’t last anywhere near as long as cool, dry and sealed.
who tests pharmaceutical stabilities for a living.
We do stability studies at two conditions (normal and accelerated(high temp and maybe high humidity)) and evaluate the chemical stability of the parental. We are looking for impurities (which occur from the natural degradation of the parental, plus in process impurities, chiral) that may not be >~1.0%.
Typically degradents will start to appear in the 6-9 mo range but are <1.0%, but by 1 year are close to 1.0%. As these impurities increase, the potency of the parental decreases (has to be in the range of 90-110%). Additionally these impurities are poisonous to our bodies, we must remember that these drugs are not natural appearing compounds like minerals, but are chemicals that we have engineered. Therefore they do degrade into body damaging impurities.
Additionally, there are clinic studies that go on for each of the drugs that are on the market. These studies include many medical test to see how the body metabolizes these chemicals, plus determine the concentration of the drug in the system.
Pharmaceutical companies compile all of this data and set an expiry date based on these studies. Just by what I have observed during testing, I would not take and expired drug.
In addition to what others have said, there’s a huge variation in stability from one drug/formulation to the next. You can stick one in an open container, under UV light, warm/humid conditions, dunk it in acid/base/oxidizer and it comes out weeks later just the same as it went in. Another drug might degrade if you just look at it funny; and half the effort in development is working out a formulation that gets it to squeak past the minimum stability requirements. There’s no way to know which is which without access to the data. (Well, if you have a very strong background in the chemistry involved, you might be able to make some educated guesses. But still.)
I used to work as an analytical chemist in pharmaceutical R&D – I wouldn’t take a random expired drug, either.