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How long can you use medicine after its expiration date?

If you've ever rummaged through the back of your medicine cabinet for a painkiller, only to come across half-finished packs of tablets you took for a bad back a decade ago, you're not alone. I regularly have patients coming in with a rattling plastic bag full of expired medicines, asking me what they should do with them. But do you really need to worry about expiry dates?

What is an expiry date?

The expiry date of a medicine is the latest date that the manufacturer guarantees that the medicine will be as effective - and as safe - as when it was issued. It's a legal requirement for all medicines in the UK to have an expiry date.

Although the date is absolute (December 2021, for instance), not all medicines stop working on the day they expire. In fact, manufacturers pick arbitrary dates - say, one or two years - after the manufacture of a batch of medicines. They check them on that date to ensure the medicine is stable and works at the dose it's prescribed.

The actual shelf life of the drug may be much longer than the date on the packet. However, this can't be guaranteed, so you should always err on the side of caution and avoid taking medicines after they expire.

What the studies say

One study looked at 122 different drug products and tested them regularly over more than five years. For almost 9 out of 10 products, testing showed the medicine stayed stable for 66 months. And a small minority was still just as effective an extraordinary 15 years later.

But these medications were kept under 'optimal conditions' and there are many factors which mean the same may not apply to medicines you keep at home - you can find out more later in this article. What's more, while a medicine may still be effective and safe a month after the expiry date, that chance goes down with every passing month. And importantly, you won't know whether your medicine falls into this category or not.

Is it sealed?

Then there's whether or not the package is sealed. Light, variations in temperature and particularly moisture can affect the stability of a medicine. That's why your medicine cabinet is a fairly good place for many products, because it's dark and isn't usually subject to huge temperature fluctuations.

Many medicines today come in foil blister packs, which keep moisture and light out. The expiry date does guarantee that as long as the blister isn't opened, they will still be effective up to that time. However, if the packaging that surrounds the medicine (as opposed to the cardboard box) is opened, that expiry date can't be guaranteed. Likewise, tablets in bottles can never be guaranteed past their expiry date.

What about temperature?

Another major variable is temperature. Some medicines (usually non-tablet forms) need to be kept in the fridge. If you leave them out by mistake, they may be less safe or less effective even before their expiry date is reached.

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How expiry dates affect other types of medicines

Any medicine that contains preservatives (eye drops are a common example) may not be safe once it has passed its expiry date. That's because the preservatives are added to avoid harmful bacteria growing in the liquid - which, for obvious reasons, is not a risk you want to take when you're putting something into your eye.

Sometimes, a shortage of medication supply means the NHS and national drug safety agencies need to check and see whether a medicine is still safe. For instance, in the last couple of years there have been shortages of adrenaline auto-injector pens, used to treat the most serious type of allergic reaction called anaphylaxis. Over that time, I've had guidance issued to me as a doctor, telling me that certain auto-injectors can be safely used up to four months after their expiry date. But you should never take this risk unless your doctor has advised it.

Liquids may have two dates - an expiry date if unopened and a shorter time-frame for use once opened. Pay attention to both!

What to do with expired medicines

If you have unused medicine that has expired, speak to your pharmacist. Your pharmacist can't re-issue medicines to other people, even if the packet is unopened, for safety reasons. However, they can often dispose of it safely for you.

If you have any one of a range of long-term conditions such as high blood pressure, raised cholesterol, diabetes, asthma, chronic kidney disease or heart disease, you may be taking several regular medications. Taking these medicines exactly as prescribed means you'll get maximum benefit and maximum protection from them. And taking steps to manage and organise your medication properly will make this a lot easier.

Although they aren't strictly medicines, sun creams and lotions definitely have an expiry date for a reason. The protection they provide becomes much less effective over time, especially if they've been opened or left out in the sun. Get rid of sunscreen at the end of every summer season or at least as soon as it reaches its expiry date.

All of which means it's a very good idea to do a regular purge of your medicine cabinet. You might want to put a reminder in your diary every six months - or more often if you take multiple medicines.

With thanks to 'My Weekly' magazine where this article was originally published.

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