Yooooowwwwwch!!! Thus endeth the debate.

I've been trying to find anything more definitive out there. Ran across a reference in Google to Auerbach's Wilderness Medicine book. I don't own this book and I need some subscription to access it online so I can't read it, but there seems to be an appendix on drug stability that might shed some light on this topic. Does anyone have that book handy who could tell us what it says about freezing meds?

Let me muddle things up with some slightly informed guesswork. The structure/conformation of the active ingredient molecules of the medicine shouldn't be affected by freezing. As temperature drops, molecules "wiggle" less and so are less likely to accidently change into something else.

However, there's a lot more stuff in medicine than just the active ingredient. In dry pills there's time-release coatings, dispersion agents, fillers, binders, and assorted other things which can be affected by lower temperatures. My main concern would be with the time-release coating becoming more brittle and cracking when cold, thereby allowing the active ingredient to hit the body quicker and in a bigger dose than recommended.

In liquid medicines there is a different thing to worry about. Usually the medicinally active molecules do not want to disolve in water so they are dispersed/suspended in the water by surfactants. The ability of surfactants to suspend the medicinal molecules changes with temperature. If the temperature drops too low an irreversible phase-change can occur which destroys the ability of the molecules to stay suspended in the water.

I have no idea if the above concerns are true for medicine, but they are things I have to worry about when designing chemical blends for oil field applications, which is surprisingly similar to medicinal chemistry. "Winterized" chemical blends for the field are a pain in the @$$.

-Blast

Asprin and Ibuprofen are relatively safe and stable.

But, Paracetamol / Acetaminophen typically only has a shelf life of two years and after this can have an upredicatable dose.
Since it's a reasonably nasty overdoze risk anyway (especially with a few drinks or a compromised liver) it's probably the OTC med I would throw out at the date.

If you're taking meds, call your pharmacist and ask.

Sue

So, to be clear, my "understanding" was not a specific document, but personal experience by continually coming across medicine labeled "store at room temperature". With what I have immediately accessible, I see that DayQuil(R) says "store at room temperature", a Peopto-Bismol(tm) chewable tablets (expired, getting tossed) says "avoid excessive heat". CVS brand of Sudafed(R) says 68F - 77F ( 20-25C). I'm pretty sure antibiotics are the same way, but the one I have an info sheet for doesn't say anything.

My concern was mostly with the freeze-thaw cycle, and knowing that other consumables (i.e. chicken) you are not supposed to eat it after re-freezing it twice. This came up because I had the Sudafed(R) and the Pepto-Bismol(tm) in a first aid kit that went on a winter camping trip. Also found out that iodine swaps apparently have an expiration date. Needless to say, most of the medicines in my kit were either exposed to below room temperature or have passed (or near) expiration.

When I have a need to swing by again, I'll ask the pharmacist. My thought is this is going to be very dependent upon the type medicine. This really occurred to me mostly because of the "After Armageddon" show and that "room temperature" should be read as "technologically controlled room temperature", less you forget that normal temperature ranges during the day is about 15-20F.

Sun cream often has a very short shelf-life, around 6 months. So this is interesting but confirms what I'd read.

Usually, medications lose their potency but don't become dangerous. Expired meds can be better than nothing. If you use the standard dosage, the worst that will likely happen is no effect. (It's tempting, then, to use a higher dose, but at that point you are just guessing and there's a real danger of overdose.)

What I'm saying is, it's not like eating food (eg rice) that's been cooked and left out for 24 hours. That does become actively dangerous. Germs grow in it.

I suspect that the 'danger' of meds is simply that they lose some of their potency, rather than becoming dangerous. I know the Army did some testing on meds in high heat, and were surprised that more stuff didn't go bad. IIRC, it was mainly some antibiotics that went bad. I think Neomycin is one with a relatively short shelf life.

The so-called expiration dates printed on the labels are not a good indication of a real expiration date, I believe that is a law. The Army testing indicated that many meds are good for YEARS.

This may have been the article: Many Medicines Are Potent Years Past Expiration Dates

Sue

Ok, I see where you are coming from. I think most pharmacists won't be particularly knowledgeable about the effects of freezing on various medications, except for certain ones which are known have problems, like insulin. I say this because I think their training would more likely emphasize storing meds in whatever temperature range the manufacturer recommends, and therefore, the conventional thinking is that storing them outside this range is "not recommended" or "bad" with little additional information to offer.

As we mentioned earlier, there's been little little research on the topic it seems so little to teach pharmacists about it. And maybe that's because freezing doesn't particularly affect most meds, at least in the short term? <shrug>

Susan pointed out a DoD study we've mentioned in the past on ETS. That was high temp storage but the results did publicize the fact that meds can still be fine beyond their expiration and storage specs, just like you can drink milk beyond the date printed on the top.

I also made another comment in the past about this topic. I'll just link to that old post . I was discussing expiration dates in that post, but it can also apply to storage conditions. Basically it boils down to "proceed at your own risk" if you're exposing meds to conditions outside the manufacturer recommended range and you should do a personal risk-benefit calculation.

If some medication is critical, like some heart medication, then by all means take extra precautions about keeping it from freezing. Or even antiotic ointment if you'll be many days from civilization in case a wound gets infected. But if you're carrying something for headaches or minor aches and pains, then you can probably be less concerned about the effects of freezing. Anyway, my personal, non-pharmacist 2 cents of advice.

EDIT: I'm still interested in finding out what that appendix section of Wildnerness Medicine says about the stability of meds at extreme temperatures, if someone has that book. Maybe there are some surprises, however, I suspect that most of the meds that shouldn't be frozen are injectable and therefore not the kinds of meds that most of us would be carrying around.

Auerbach's excellent books Wilderness Medicine and Field Guide to Wilderness have an appendix entitled Drug Stability Information. The initial sentence is: "Stability data on drug products are derived from studies don in controlled enivormnmental conditions."

A typical use-at-your-risk disclaimer follows, for instance, at the end of the acetaminophen listing: "...Avoid freezing. Stability after freezing is unknown."

Assessments for each listing are quite conservative, and would seem to be based more on appropriate caution because so little cold-weather testing has been done, and therefore there is little real data on which to make recommendations.

It should go without saying that the pharmaceutical manufacturers and sellers have a clear vested interest in selling more product rather than less. The previously mentioned Air Force study is a clear example of most drugs being useful far beyond their printed "expiration date." It's not clear to me what the storage conditions were for the Air Force study; if anything cold weather storage/freezing conditions should make medicines last longer. Pills, capsules, and powders at least, contain essentially no water, so there should be no freeze-thaw cycle concerns as with freshly frozen food-stuffs. Many meds in syrup form are alcohol based, so have their own anti-freeze built in, to survive the low temperatures without freezing most of us have to deal with.

I'll restate an important point. With the exception of tetracycline only, which may degrade into a substance toxic to the kidneys, what happens at some point is loss of potency. There appears to no evidence that you're going to poison yourself by using 6 year old Tylenol or Advil.

I typically use prescription and OTC meds for several years beyond their expiration dates (the exception would be outdated tetracycline); the listed dates are in the drug companies and re-sellers best interests, not mine. I'm willing to wait to see published evidence of harm.

Further research on this would be of interest, and inexpensive to do. I don't think industry funding for it, however, would likely be forthcoming.