by Elizabeth Ducie

Created on: March 20, 2009

We've all done it at some time in our lives. We've gone to the medicine cabinet looking for a tablet or other medicine that we need in a hurry. Maybe we've got a headache and need to clear it because we've got a busy day. Or maybe a child has fallen over and needs a graze soothed. Most times, we grab what we need and use it without a second thought - and certainly without checking the expiration date on the pack. Unfortunately, there's a good chance that the medicine is out of date. After all, up and down the country, there are medicine cabinets stuffed with expired medicines.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /

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What is an expiry date?

Companies establish expiration dates by stability studies carried out as part of the development activities leading up to licensing of a drug. This does not mean a drug with a three year expiration date stops working, or becomes dangerous, on the first day of year four. It does mean however that there is no information available on the effectiveness or safety of the drug after the end of the shelf-life.

All medicines are made up of active ingredients (the chemical that provides the required remedy) and other materials such as binders to hold tablets together, sugar to mask the taste of the active ingredient or water to dissolve the active ingredient.

All drugs have a strength or potency stated on the pack. For example, paracetamol can be bought as 500mg tablets or capsules. This means that each tablet has been manufactured with a target quantity of 500mg. According to the product licence, there will actually be a range within which the drug is safe and effective. This might be for example 95 - 105% of the stated label strength.

When a medicine is manufactured, it is tested to make sure it contains the right quantity of the active ingredient (such as paracetamol). If the result lies within the permitted range, the batch of medicine is approved for sale. However, over time the potency of the active ingredient declines and at some point it will fall below the effective level. We know that this will be after the expiration date but we don't know whether it will be one day, one month or one year afterwards. Beyond the expiration date is the unknown.

Risks of using expired drugs

It's quite possible there will be no ill effect from using a medicine after its expiration date. However, we are taking a huge risk when we do this and it's not something that should be done lightly. No pharmacist or doctor

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