I recently found a packet of ibuprofen that had expired. What happens to drugs such as these, and paracetamol, after expiry? Are they less efficacious or even harmful? They looked just fine although I thought it best not to take them.
We are grateful to Tony Holkham of Boncath, Pembrokeshire, UK, for pointing out that official medical advice is never to keep or take out-of-date medicines. Please bear that in mind while reading the following 鈥� Ed
鈥� All medicines undergo stringent testing before they are marketed to ensure the active ingredient remains within an acceptable limit 鈥� usually at least 95 per cent of the amount stated on the label 鈥� throughout its shelf life, and that any degradation products are not more harmful than the original medicine. This shelf life is determined by carrying out stability trials on the medicine in its packaging.
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Once a drug has expired, degradation continues and the content of active ingredient would be expected to decline. Tablets stored in bathrooms are likely to be exposed to more humid conditions and wider variations in temperature than when stored in a warehouse or pharmacy, so loss of the active ingredient may happen more quickly.
鈥淥nce a drug has expired, the content of its active ingredient would be expected to decline鈥�
The appearance of the tablets is not a guarantee of safety, but any tablets that appear to be more friable than usual, broken, clumped together, 鈥済rowing鈥� crystals, or otherwise not as expected should be considered suspect. In the case of aspirin, an odour of vinegar suggests the active ingredient, acetylsalicylic acid, has decomposed to salicylic acid and acetic acid. While is an effective painkiller, it carries a greater risk of internal bleeding than aspirin.
For out-of-date tablets, a risk/benefit analysis of whether or not to take them might include factors such as how far past the expiry date they are, how bad the pain is, and the availability of other pain relief. This does not constitute a recommendation, but an out-of-date pack of pain-relieving medication rejected during the evening may be very welcome at 2 am after several sleepless hours! Never take more than the stated dose 鈥� whether the pills are out of date or not.
Different considerations apply to liquid medicines. Not only are active ingredients more likely to degrade in a solution, the microbiological risks also become more significant. I am sure no readers sip cough medicine directly from the bottle in the bathroom in the middle of the night 鈥� but the consequences for future doses should be obvious.
Hillary Judd, Exeter, Devon, UK
鈥� Any drug must have an expiry date. However, this doesn鈥檛 mean that immediately after this date the drug starts to undergo a degradation process and produce toxic by-products. Many compounds are highly stable if kept under good conditions, such as at room temperature, away from light and moisture.
A 2012 study in the , in which various common prescription drugs were analysed between 28 and 40 years after their expiry date, revealed that drugs such as paracetamol (acetaminophen) and codeine contained more than 90 per cent of the initial amount of active ingredients, whereas compounds associated with aspirin were much more degraded.
Some drugs do form toxic products when they degrade. For example, tetracycline antibiotics are not very stable and can form degradation products that are toxic to the kidneys. So it all depends on the drug and the conditions of conservation. Some you can possibly take after the expiry date, but others you should avoid.
Olivier Sorg, Swiss Centre for Applied Human Toxicology, University of Geneva, Switzerland