How is ‘expiry date’ of medicines determined?

Some decades ago there were no chemists’ shops. Instead of chemists druggists used to mix various compounds according to physicians’ prescriptions and sell them either in powder form or liquid form. Sometimes physician’s assistant used to prepare such mixture in the dispensary itself so he was known as compounder. These types of medicines did not require a cautionary notice of ‘expiry date’ to be written on the label because patients used to consume the medicine within a few days.

Over a period of time pharmaceuticals manufacturing companies started manufacturing and selling such compounds in the form of tablets and capsules. Chemists’ shops replaced druggists’ stores. Now there was no longer certainty that tablets and mixtures were consumed immediately after production. If medicines remain unused for a long time some changes may take place in the properties of the ingredients due to heat and moisture. This would reduce efficacy of medicines, so it became essential to write ‘expiry date’ on the packaging material of medicines.

Medicines are made to go through strict stability tests to determine expiry dates. When a drug is exposed to heat, moisture, and humidity, it will result in some changes, usually negative. In such scenarios, the medicines typically degrade. The process of degradation highlights the decrease in the effectiveness and amount of the active pharmaceutical ingredient, which is the primary drug itself.

Additionally, the compounds that have degraded are termed as ‘impurities.’ Impurities are formed as a direct result of the magnitude of time and stress the medicines are made to go through. What this means is that even if the magnitude of time and stress is minimal, there are high chances of medicines degrading overtime.

Pharmaceutical companies initially perform a series of tests known as ‘Forced degradation studies.’ These studies are meant to observe and determine the potential impurities that could arise for the drug. Moreover, during the tests, the drug is exposed to extreme factors of stress, such as peroxide, acid, base, UV light, and heat, etc. Post-detecting the potential impurities, the main drug that is being used to produce the medicine and also marketed, is put through ‘Stability tests,’ which involves testing the formulation for stability by storing it in different zones of temperature.

At regular time intervals, the samples are withdrawn to observe potential impurities that might have formed while the process was taking place. Once the impurities have been observed and are within limits, it is determined that the formulation was satisfactory, which means that it passed the stability tests and studies. The pharmaceutical company set an expiration date based on the time and the temperature zone it was kept-in.

Expiration dates are argued by many today. Some even term them as myth or fake. However, you cannot deny that there is a lot of research and study behind every medicine and, as already mentioned, are subject to several studies and tests. Different drugs react differently to stress conditions, and that is primarily the basis of which expiration dates are set. Even though consuming a medicine after its expiration date may not result in something serious, but there are many cases where people have experienced serious health conditions just because they consumed a medicine or medicines past their expiration date.