Concept of 'Safety'

Concept of safety of medicines

While efficacy of a medicine is related to benefit, the safety of a medicine is related to the associated risks after it is taken by a patient. The safety of a medicine is extremely important. Even though no technology is completely safe, the benefit of taking a medicine must exceed the risks of taking it. In other words, the undesirable or adverse effects (side effects) of taking a given medicine need to be evaluated in relation to:

  • How likely they are to occur, and
  • the benefit of taking the medicine.

This is also called the benefit- risk relationship.

Safety and acceptable risk

A medicine is considered sufficiently safe if the risk associated with taking it is acceptable for:

  • Patients;
  • healthcare professionals; and
  • the Regulatory Authorities allowing the medicine to be marketed.

The acceptable risk level may vary between these groups. Experience has shown that some patient groups are more willing to accept higher risks than Regulators and healthcare professionals.

Benefit Risk

Safety and indication

The medical problem (or indication) needs to be specified to evaluate the safety of the medicine. Let’s look at another example.

Example 2
Susan, an 85 year-old woman is diagnosed with breast cancer. The tumour is located at a critical place, and so she cannot undergo surgery. The doctors say that by treating her with chemotherapy it is possible to kill the cancer cells and cure Susan. Without chemotherapy, the tumour cells will most likely spread to Susan’s organs (metastasis) resulting in a life threatening condition. However, the doctors tell Susan, that chemotherapy may result in bone marrow suppression, depression of the immune system leading to infectious diseases and other serious side effects.

By accepting chemotherapy, Susan will most likely extend her life expectancy. She values the risk of chemotherapy acceptable compared to the risk of dying from cancer.

Another example.

Example 3
Ben, a 10-year-old boy, suffers from psoriasis. Once a year, he has rashes covering his entire back that last for about a week. It is possible to relieve psoriasis with chemotherapy, but is it worth it when thinking about safety?

In Ben’s situation, he has a long life ahead of him. Susan is 85 years‑old, which is above the average life expectancy (83.5 years for women in the EU as per 2017). In contrast, Ben, as a male EU citizen, has an average life expectancy of 78.3 years. Although psoriasis is a very unpleasant condition, the risks associated with chemotherapy are considered too high compared to the benefit of relieving a rash that occurs one week per year. In this situation, chemotherapy would be considered inappropriate.

Examples 2 and 3 highlight that the safety of a given medicine must be evaluated in relation to the specific medical problem that it is intended to treat – the indication. This is exactly what the authorities do before they allow a medicine to be marketed.

Inside the box that any medicine comes in, is a package leaflet that shows the medical condition(s) or indication(s) that the medicine is marketed to treat (approved for). The medicine is considered safe to use for the condition(s) stated in the package leaflet.

Safety and population

The population is another important factor when looking at the safety of a medicine. If you think of Ben (child) and Susan (elderly) from Examples 2 and 3, their ages differ significantly and they belong to different populations in the medical sense. Due to their different physical status, they might tolerate a given medicine differently. Therefore, the risk of using the medicine might differ between them.

Safety and condition

The conditions for use also influence the safety of a medicine. To ensure its safety, a medicine must be taken at a specific time and in the specific dose. All of this is also stated in the package leaflet under a special heading ‘How to <take> <use> X’.

Safety and interactions

Possible interactions with other medicines and/or foods must be taken into account.