© 2014 Roy Benaroch, MD
Mernga wanted to know about drug expiration dates. Do drugs really “go bad”? Or this is just a scam to get people to buy fresh medicine?
The truth is, they’re a little of both.
There are sometimes two separate “expiration dates” on a prescription medication. The first is the one stamped on the package by the manufacturer. You’ll see that one if what you have is in the original packaging, like a tube of ointment or a small bottle of eye drops, or a bottle of pills if you’ve been given an original bottle straight off the shelf. Sometimes the manufacturer’s stamp is on a box that the tube or bottle came in (the one you’ve already thrown away.)
The manufacturer’s stamped expiration date is a promise that the medication will keep its potency at least until that date, if it’s been stored correctly. It doesn’t mean that on that date it will actually go bad, but the manufacturer is saying, look, if you use this stuff past the date, we’re not responsible for it any more.
It turns out that many medications will keep at least most of their potency for a while after that date. The best studies that are looking into this are sponsored by the US government through “SLEP”—the Department of Defense Shelf Life Extension Program. This program tests the potency of medications that are kept in long-term strategic stockpiles for the government. It turns out that the feds are keeping big stores of anibiotics, morphine, antihistamines, and many other essential medications for use after The Zombie Apocalypse. To save money, they keep the medicines well-past their expiration dates, while testing selected lots for potency. On average, medications in the program are lasting 5-6 years past their dates—some lasting 15 years or more.
However, the drugs in this program are stored until optimal conditions, in a cool, dark, low humidity facility. They’re all in their original packaging, too. Drugs really can be sensitive to storage, and can rapidly lose their punch if exposed to heat or light, or if they’re moved from bottle to bottle, or removed from foil seals. Also, there’s a lot of variability in the shelf-life of medications, even between lots of the same medication. So though we know that most drugs will last past their dates, it’s hard to know specifically what medications on your shelf will last just a few months longer, or several years longer.
The form of the medication does seem to be important. Hard, dry pills last longer than creams or ointments or liquid drops. Reconstituted suspensions (where the pharmacist adds water and mixes it at their store) last the shortest, and are the most vulnerable to heat and storage conditions.
Though the main issue with older, expired drugs is potency—some get weaker with time—there’s been some concern that at least some medications actually become toxic when they’re old and past their prime. The classic example of this is an older formulation of tetracycline, which was reported in the 1960’s to become toxic to the kidneys if used well past its expiration date. That form of tetracycline is no longer sold in the USA, and it’s not really clear to me if that reaction was ever substantiated. I don’t think there’s much risk of old medicines becoming harmful—it’s more that they might not work as well or as reliably.
There’s a second date that will appear on any prescribed medication, a date typed on by the pharmacist that is usually 12 months after the prescription was filled. This date is added to discourage hoarding of medicines—after all, it may be unlikely that something prescribed a year ago is still needed. It also may be true that my moving pills from the original container (a big bottle) to the new container (a little bottle) they’ll lose some of the manufacturer’s guaranteed protection against aging. Though I don’t want anyone to hoard medicines, especially antibiotics and narcotics, depending on what the medicine is used for it sometimes makes sense to keep a medicine past the pharmacist’s date for occasional use. When in doubt, ask your doctor.
The bottom line: these dates are a guide, but for non-critical medications, especially if you’ve been good about storage, it’s probably fine to keep using them past their prime. If the medication is critical, I’d go ahead and keep an eye especially on the stamped manufacturer’s date. Stay safe, and keep important medicines fresh.