WHY DO MEDICINES HAVE A VALIDITY PERIOD?

Comes this time and, despite the heat that can still be felt this year, we start to have at the counter those situations of colds and coughs that sometimes result in the following exchange of words: “I would like to * cof * cof * cof * * sound of cat to be strangled *”.

Immediately upon being presented with the medicine that I suggest, the answer is “Ah, I still have at home the same from last year, it should be good. Thank you.”

Why do drugs have expiration dates?

Things spoil: it’s a fact of life. What surrounds us are atoms in colliding molecules, constantly changing. Sometimes, the change is slow, like when we talk about the decomposition of some plastics that we know can take hundreds of years… Sometimes, it is fast, like when we leave the soup outside the refrigerator and after two days it is sour. From these examples we can see two things about changing medicines:

• Depends on the conditions in which they were stored (whether or not it was cold);
• It depends on the type of thing it is (whether it’s plastic or soup or something).

The processes that cause medicines to go bad are many and varied, but the important thing to remember is that because they are synthesized in the laboratory or because they appear in a form that looks more or less invulnerable, it does not imply that they do not degrade. When a medicine is authorized to be marketed, it must come with some “stability studies”, i.e., information on what happens when it is exposed to certain storage conditions for a certain period of time. It is on this basis that the “actual” shelf-life of the medicinal product is calculated, and then, for safety reasons, the shelf-life is shortened slightly to be sold.

So yes, it is true that the medicine is often “good” even after the printed expiration date, but depends a lot on several factors, which cannot be guaranteed by any health professional:

• If it has been stored in ideal conditions: inside its original packaging, with minimum contact with air, light, and intense heat above 25°C;
• If it is not a product that has a validity after it is opened. Usually, his can be seen in drops, syrups and ointments, and may appear in the form of a symbol with an open cylindrical carton, with a 6M or 12M written. After opening a product, it comes in contact with the air and this is often enough to initiate an accelerated process of degradation: thus, this warning written on the packaging.

But what is this degradation?

As I have already mentioned, the processes can be many, but the result is more or less simple: Molecule A, which was our active substance (the one for which we take our medicine), ceases to be molecule A and becomes its cousin. This cousin is sometimes cool, but usually is not: either because it does not have all the effect it needed to have, or because it may even have negative effects.

By way of conclusion, what should we do about out-of-date (printed or post-open) medicine or less-than-adequate storage? Deliver them to the pharmacy.

In a more urgent situation, when the deadline has been exceeded, you can talk to your pharmacist to see if it will be something that could be punctually infringed, but it is by no means the general rule: when we talk about medicines we should always play it safe and it is not worthy to put ourselves at risk unnecessarily.

Text written by João.