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24 Aug 2025
8 Min Read
Ms Lim Jia Hui
You know the drawer. The one crammed with old receipts, stray batteries, and half-used packs of medicine. One day, you rummage through it and spot a strip of pills—expired a year ago. You pause. Is it still okay to take? The pills look fine. No odd smell. But that expiry date nags you. Should you toss them, or take the risk?
We’ve all been there. Yet behind that tiny printed date lies a big question: how long do medicines really last, and who decides when their time is up?
The expiry date is the final day a manufacturer guarantees full potency and safety, as long as the medicine is stored according to the instructions. It applies to unopened products in their original packaging and is determined through rigorous stability studies. Once the container is opened, the stability of the product can change significantly, as exposure to air, light, and moisture can speed up degradation. This is why a product that remains stable in its sealed container may not last as long once opened.
Pharmacists may also assign a beyond-use date (BUD) when medicines are repackaged or dispensed in new containers, which is often shorter than the manufacturer’s expiry date. Both expiry dates and BUDs are determined through long-term (real-time) stability testing, which observes a product under normal storage conditions, and accelerated testing, which subjects it to higher temperatures and humidity to simulate ageing. These tests examine chemical potency, physical appearance, microbial growth, and even the product’s functionality, such as whether tablets dissolve properly.
When a medicine passes its expiry date, two main risks arise. The first is loss of potency—the gradual weakening of the active ingredient until it no longer delivers the intended effect. The second, although far less common, is the formation of toxic by-products that could harm the body. For example, aspirin can slowly break down into acetic acid, giving it a sharp vinegar-like smell, while older formulations of tetracycline were once linked to kidney damage.
Think of it like a bottle of fizzy drink left open for too long. It may still look the same, but the fizz—the part that makes it work—has gone flat. In medicines, that ‘fizz’ is the potency, and when it’s gone, the drug can’t perform its job.
For most common tablets, such as paracetamol for headaches, ibuprofen for muscle pain, or antihistamines for allergies, expiry doesn’t mean they suddenly turn poisonous at midnight on the printed date. However, the drop in effectiveness can be dangerous for certain medicines where every milligram counts. Imagine someone with heart disease relying on nitroglycerin during a chest pain episode, only to find the expired tablets no longer work. Or a person with diabetes using insulin past its prime, leading to unstable blood sugar levels. Even in epilepsy, where medication must be precise to prevent seizures, a weakened dose could mean the difference between control and crisis.
Surprisingly, the answer isn’t always a straightforward no. In the United States, a government initiative called the Shelf Life Extension Program (SLEP) tested thousands of batches of medicines that had been kept under secure, climate-controlled conditions. The results were eye-opening—88% of the tested drugs were still potent for one to five years beyond their printed expiry dates. For the US military, which manages vast medical stockpiles, these findings translated into millions of dollars saved.
But here’s the catch: those results came from medicines stored in perfect conditions. Imagine them locked away in temperature-controlled rooms, shielded from sunlight, moisture, and sudden temperature changes. In Malaysia, the reality is very different. Our hot, humid climate places us in Zone IVB for stability testing—a category that predicts faster degradation compared to cooler, drier environments.
Medicines in Zone IVB countries like Malaysia, Singapore and Brunei are tested to survive in ‘sauna-like’ conditions—30 °C with 75% humidity all year round. This is why proper storage matters so much in our climate because your medicine is already battling the weather before you even open the box.
In some cases, yes. How you store a medicine can determine whether it remains effective until its expiry date or loses its potency months earlier. Heat, light, and moisture are the biggest threats to drug stability. For example, a strip of tablets kept in its original foil packaging in an air-conditioned bedroom may remain potent well beyond its labelled date, while the same tablets stored in a stuffy, sunlit room or next to a heat source could degrade much faster.
This is why pharmacists consistently emphasise proper storage. Medicines should be kept in a cool, dry place, ideally below 25°C, and always in their original packaging to protect them from air and moisture. In Malaysia’s climate, that often means avoiding storage near windows, in kitchens, or in non-air-conditioned spaces that become warm during the day. Before taking any medicine, whether expired or not, it is worth checking for changes in colour, texture, or smell, as these can indicate that it is no longer safe or effective.
Pharmacists assess poorly stored or expired medicines for safety and potency, consult manufacturers when needed, and advise disposal if in doubt. They educate patients on proper storage, signs of spoilage, and report degraded products to improve medication safety.
Some medicines should never be taken once they have expired, no matter how normal they appear. Insulin can quickly lose potency, making it unreliable for blood sugar control. Liquid antibiotics may degrade rapidly, reducing their effectiveness in fighting infections. Eye drops risk bacterial contamination once opened, which can lead to serious eye problems. Nitroglycerin, used to treat chest pain, is highly unstable and can fail when needed most.
Biologics and vaccines are particularly sensitive, and even small changes in temperature can affect their safety and effectiveness. For these medicines, taking a chance is simply not worth the risk.
Expiry dates aren’t just random numbers printed on a box. They are the result of careful experiments, strict regulations, and the work of people trained to protect your health. While some medicines can last longer under perfect conditions, the reality in Malaysia’s climate is very different. Heat, humidity, and poor storage can shorten a medicine’s life without you even realising it.
This is where pharmacists make all the difference. They are the ones who understand the science behind every tablet and bottle, who can tell you whether a medicine is still safe, and who ensure that each dose works exactly as it should. It’s a role that combines science, problem-solving, and real human impact—skills that go far beyond counting pills behind a counter.
So, the next time you come across an old strip of tablets at home, remember: that tiny printed date carries a whole world of science and responsibility behind it. And if you’ve ever wondered how it all works, or imagined yourself as the trusted expert making those decisions, starting with a foundation in science and progressing into pharmacy could be the path that opens that door.
