All things come to an end – but why medicines?
Your medicine chest is well stocked, you are prepared for an emergency, but fortunately you stay healthy. Then one evening, you do get headaches or other symptoms, or your child has stomach pains. And while rooting through your medicine chest you realise that the medicines are way past their expiry date. Why do medicines have an expiry date anyway? And can you still take out-of-date medicines? Here are a few answers.
Manufacturing medicines is not rocket science. It should always focus on the active ingredient. This has certain properties and effects, which can for example be pain-relieving, circulation-stimulating or immunosuppressive. The list of effects is long. To apply these effects specifically, some active ingredients need catalysts, which is to say ingredients that have no or hardly any effect in themselves, but can strengthen the properties of the active ingredient being used. In the case of applications on the skin, these can be e.g. permeability catalysts, which can mean, for example, that a cream contains an excipient that helps it to penetrate deeper into the skin.
This mixture of active agents and excipients forms the foundation of a medicine. Then, however, the most important question arises: how and where in the body should the medicine take effect? Because a formulation has to be chosen depending on whether it is taken orally, but should not dissolve in the stomach, whether it must be inserted as a suppository, or whether it should be metabolized hepatically (by the liver). During this process, the galenic aspects are determined – e.g., cream, lotion, chewable tablet – as well as the physical form. A tablet is stable and can often pass through the stomach, a suppository dissolves slowly, a chewable tablet takes effect locally and a liquid passes quickly into the bloodstream.
Other excipients are required for these different forms; for tablets this is frequently lactose, for creams it is often anhydrous wool fat or similar substances. Depending on the composition of the medicine, the actual cocktail of active ingredients – the foundation – may break down after a long time in storage. In addition to this, impurities can develop over time, especially in liquid or cream-like products and in products that have already been partially used. When this happens, the use of a product can unintentionally cause penetration by bacteria. These processes can influence the intended effect of the medicine.
In order to be able to make an approximate statement about such processes, medicine manufacturers subject their own products to laboratory testing. This also includes a stability test, in which the concentration of the active ingredient is tested after three, six, twelve and twenty-four months under unfavourable storage conditions. Then, if all the other tests and conditions have been met, the medicine can be approved. If stability has not been verified beyond this two-year test period, the manufacturer can only safely give a guarantee for these two years.
In most cases, the active ingredients are still effective after the expiry date. But one of the excipients may have transformed. Impurities can develop in liquids over time, especially in products that have already been opened. Then, the active ingredient could still have a completely normal effect, but taking the medicine might, for example, cause stomach upsets, or the cream might irritate the skin instead of soothing it.
The expiry date on medicines is therefore not a trick played by the pharmaceutical industry to force people into making new purchases, but just a guarantee that a medicine has the described effect within the stated period. It is up to the user to decide whether they want to use the medicine beyond that period. But then the manufacturer’s warranty ceases to apply.
Conclusion: the date stated on the packaging is for the safety of the medicine and ultimately of the patients. Out-of-date medicines should not be disposed of in the household waste and under no circumstances be flushed down the toilet. Pharmacies and chemist’s shops in Switzerland accept unused and out-of-date medicines for correct disposal.