Scrutable

For food there are "Best before" dates (as in, after this date, it's still fine, but don't write in to say it's stale) and "Use by" dates, as in "Hmmm, after this date it might be full of nasty bacteria".

For medicines, I presume that they don't muck about with "Best before", so we ought to throw our pills away once they go past their date. But in practice, how bad can it be?

I ask because I'm going through some dark cupboards as part of our first house move since 2006 and finding some very basic medicines (loperamide, paracetamol, pseudoephidrine) that are 2-3 years out of date. I refuse to believe that these products (which typically have at least 2 years of use-by when you buy them) have turned into either inert dust or anthrax, so I shall just bring them to the front of the medicine cabinet. But does anyone know if there are any medicines where a solid pill goes rogue over time? I'm guessing maybe antibiotics, but you're not meant to keep those anyway because you should have finished the course.

(Yes, obviously the safe answer is "Don't use anything past its date", but I want the nerd angle on this.)

From memory I think it's mostly about a reduction of efficacy, and the biggest problem is no-one knows how big a reduction so you can't easily adjust the dosage. A very quick google suggests my memory is working for once.

Certain meds’ expiration dates may matter more than others. “Insulin and nitroglycerin [which is used to treat chest pain] are known to very quickly lose their potency and therefore should not be used past expiration dates,” notes Dr. Rohr. Other drugs that shouldn’t be consumed after their use-by date include liquid antibiotics, which aren’t as stable as their pill counterparts, and some injectables. Norepinephrine (used to treat shock and low blood pressure), for example, should be discarded if you notice discoloration, adds Dr. Rohr.

The US Army* did some work on this, but I suspect their results are not easily applicable to you, as they made some reasonable assumptions about the drugs having been stored in known and stable conditions in military warehouses.

*Probably the DoD

https://www.astho.org/Programs/Prepared ... act-Sheet/

https://nextgencombatmedic.com/2018/01/08/expired-meds/

https://www.health.harvard.edu/staying- ... n-anything

I can only speak for one pharma* but certainly for solid dose medicines and oral liquids, stability studies show maintenance of potency for at least two years, past use by date.
I suspect tom p may have more knowledge, as stability data has to be part of the submission for a production licence


*I am pretty sure all pharmas will do the same

Typically it is rising levels of impurity that limits the expiry in a stability study, rather than loss of assay (sweeping generalisation). If your assay falls from 99.8% to 99.6, that’s still in spec, but if imp A rises from 0.001% to 0.01% that’s a fail. (made up values and units, but you get the idea).

As was pointed out above, storage conditions have a big impact. That bathroom cabinet above the radiator is probably much warmer and more humid than a temperature controlled warehouse running at 21C with automatic alarms. Which is why there are accelerated stability tests that estimate what the medicine looks like at 2 years, but done in 6 months in an incubator.

I wouldn’t bother to keep things like paracetamol that was past expiry, given they cost less than 50p for a pack. Anything else - are you likely to need it before you can get a fresh prescription? If no, throw it out, if yes, go and get a fresh prescription now.

Beaker wrote: ↑

Wed Jan 29, 2020 8:58 am

I wouldn’t bother to keep things like paracetamol that was past expiry, given they cost less than 50p for a pack. Anything else - are you likely to need it before you can get a fresh prescription? If no, throw it out, if yes, go and get a fresh prescription now.

By which (bold) you of course mean, return them to a pharmacy. Do not throw medicines into general waste they leach into water courses and continue to have effects beyond where they're wanted.

Liquid medicines I'd be wary of keeping. There's an increased chance of growth of bacteria etc, and also a higher gas exchange meaning they're more likely to have oxidised or hydrolysed, although maybe the bottle seal is very good.

For solid pills etc, I probably haven't noticed how old any of mine are... If they've discoloured or changed texture definitely not worth using

Stability samples will have been stored at a variety of temperatures (and humidities, but maybe not "bathroom conditions" ) and will have to have passed Pharmacopoeial requirement, inc impurity levels
eta For the whole shelf life + , not just accelerated tests. This will also have been done for production samples

Indeed they are. There will also be studies representing the most challenging climate zones - for example


Zone IV- For hot climatic zones: relative humidity (%) 75±5 for 6 months @ 40+-2.

My bathroom is probably 40+1-38

Stuff from WHO here, which references the more relevant territory regulators.
http://www.paho.org/hq/dmdocuments/200 ... ort_34.pdf