By Michael Cole in The Conversation.
It is estimated that there is a staggering £300m worth of medicine unused in the UK every year. But is it safe to take these medicines if they are past their expiry date?
Expiry dates are put in place after rigorous trialling and controlled experiments to ensure the safety and effectiveness of the drugs people take. In short, they guarantee the potency of the drug. Medicinal drugs are all chemicals and the rate at which they go off will depend upon their chemical structure, the drug preparation, how they are packaged, environmental conditions, whether they are subject to microbial contamination and their exposure to heat, light, oxygen and water.
The drugs are sold in a variety of containers including bottles, blister packs, tubes and ampules. They are relatively secure while sealed. But once the seal is broken, the process of “going off” accelerates.
Let’s look at an everyday drug like paracetamol. This is an “over the counter” medicine, freely available, which helps to reduce pain or a fever. Paracetamol is sometimes sold in brown sealed bottles. The seal keeps moisture and atmospheric oxygen out. The brown bottle keeps UV light out as this can also cause the drug to breakdown. Once the seal is broken, the tablets are exposed to water and oxygen in the air and breakdown begins.
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