How is the expiry date of a medicinal product determined?

For this purpose, the applicant must carry out studies and determine the shelf life for the medicinal product as well as any special storage instructions. The shelf life of a product can range from a few months to many years. 

For each medicine, all relevant quality characteristics are summarised in a so-called "specification". In this specification it is determined whether or to what extent the active ingredient content may be reduced so that the indicated efficacy is still fully guaranteed.

Quality tests for medicinal products

In addition, toxicologically justified limit values are set for any degradation products in order to ensure that no undesirable effects are caused by such impurities. A number of further quality-relevant tests are added depending on the dosage form. For example, in the case of tablets, the time during which the active substance is released must be defined, or in the case of parenteral administration - such as infusion or injection solutions - sterility must be guaranteed. This accumulation of requirements very clearly describes and defines the quality of each medicinal product and is therefore objectively verifiable.

International guidelines: Shelf life tests

International guidelines specify exactly how shelf life studies of drugs are to be designed. Amongst other things it is defined how many batches have to be stored under which specific conditions and for how long. Real-time studies must be carried out that simulate the shelf life under real-life conditions, i.e. usually at 25°C and 60% relative humidity. In addition, accelerated studies should be initiated in which the drugs are stored at 40°C and 75% relative humidity to cover worst-case situations (such as short "outliers" during transport). The light sensitivity of the drug is also tested in separate studies.

Result: Shelf life and storage instructions

As a result of these investigations, the applicant shall determine the shelf life and any special storage instructions, which shall be approved by the authorities and listed in the Summary of Product Characteristics (SmPC) and the package leaflet. The labelling of the package also contains the expiry date together with any storage recommendations.

In the case of multi-dose containers, e.g. for oral liquids or ointments, the shelf life after opening must also be tested. The use of the product must be realistically simulated and the shelf life and storage conditions for after opening must be determined. Suitable measures must also be taken to ensure the microbial purity of these products and, if necessary, preservatives must be added.

Similar tests must also be carried out when products need to be prepared to be ready for use, i.e. concentrates need to be diluted or powders need to be reconstituted. Appropriate shelf lives and storage conditions must be specified for the unopened as well as for the prepared medicinal product.

Storage

Unfortunately, in most cases it is not possible to determine by sight whether a medicinal product can still be used after improper storage. In the case of solutions, discoloration and/or precipitation may be an indication that a medicine has already degraded, unless such changes are explicitly mentioned in the package leaflet.

Factors that have a negative effect on the shelf life: high temperature, humidity and light

Generally, three main factors can negatively influence the shelf life of a medicine: high temperatures, high humidity and light. The worst place to store medicines is therefore the bathroom. However, many people still store their medicines there. It is advisable to store medicines in cooler rooms, such as bedrooms, out of the reach of children. If light protection is required for a medicine, this protection is usually ensured by the outer packaging. This is the reason why it is important to store the medicine in the cardboard box that it was sold in. The package leaflet should also always be kept, as it contains important information on the use of the medicinal product.

Storage at room temperature

Most medicinal products can be stored at room temperature (up to 25°C), storage under refrigeration is explicitly stated in the package leaflet and the labelling of the package. Generally, it is not advisable to store all medicines in the refrigerator since with the exception of those products that explicitly require such storage conditions (e.g. for vaccines and insulin), this can lead to a loss of quality. For example, active ingredients in solutions can precipitate due to cold, and the consistency of ointments can change adversely. Deep-freezing of vaccines destroys the effective components and therefore also leads to a significant decrease in efficacy.

In the case of antibiotic powders for oral solution, the drug in powder form may often be stored at room temperature for many months and years, but the suspension made ready for use must usually be kept refrigerated and may only be used for a few days due to its shorter shelf life.

Do not leave medicines in the car!

Especially during the summer, temperatures of over 60 to 70°C can quickly be reached in a car, destroying almost every medicine.

Storage of vaccines

Generally, patients obtain the vaccine from the pharmacy. If the vaccine is not immediately injected by a doctor, it is essential that the temperature for transport and storage specified in the package leaflet and the labelling of the packaging is observed.

Since vaccines are sensitive to light and heat, their effectiveness and tolerability may be impaired if stored improperly.

The following must be observed when transporting vaccines:

When transporting vaccines in cooling bags, care must be taken to ensure that no frozen cold packs (-20°C) are in direct contact with the vaccine packaging, as the vaccine may freeze.

Vaccines that do not require refrigeration can be transported or stored outside the refrigerator for a few hours. However, temperatures above +25°C and direct sunlight must be strictly avoided.