How do we know what the side effects are?

When a new medicine is being developed, a series of clinical trials are run to see how effective the medicine is and also to identify side effects. More information about side effects is collected after the medicine has gone on sale. Read more about how we find out what a medicine’s side effects are.

How do we know what the side effects are?

Information about side effects is gathered in two stages:

  • before the medicine is approved
  • once a medicine goes on sale.

Before the medicine is approved

When a new medicine is being developed, a series of clinical trials are run to see how effective the medicine is and also to identify side effects. These trials often involve comparing the medicine with a placebo.

As part of these trials, all participants are asked about how they feel. The questions aren’t simply related to the obvious and sought-after effects, but to all aspects of the participant’s health.

For example, a person in a trial for a new medicine for arthritis will be asked not only about pain and stiffness, but also about possible headache, nausea, itchy eyes, diarrhoea and many other facets of their health.

The researchers then record what proportion of participants mention any particular symptom. If the symptom occurs more often in those who took the medicine being tested than in those who took the placebo, then it is listed as a potential side effect of the medicine. The process is rigorous and systematic, and provides a lot of information about the side effects occurring in the types of people in the clinical trials.

When a medicine is going through the new drug approval process before it can be sold, all the information on its potential side effects must be sent to the regulatory authority responsible for approving the medicine. In Australia, this authority is the Therapeutic Goods Administration (TGA).

All the known side effects for a medicine have to be listed in its product information (PI) leaflet for health professionals, and its most significant side effects need to be included in the medicine’s consumer medicine information (CMI) leaflet.

You can search for and download the CMI leaflet, or you can ask your pharmacist. You can also search for the CMI or PI leaflets for your medicine on the TGA website.

New medicines need to be tested for safety before they are approved, but in most cases they are tested in no more than a few thousand people. This means rare side effects (i.e. those occurring in fewer than 1 in 1000 people) will usually not show up until more people have taken the medicine.

Once a medicine goes on sale

Once the medicine is approved for use, it will be taken by a broader group of people in a wider range of circumstances than were involved in the initial clinical trials. Collecting information about side effects after a medicine has been approved for sale is called post-marketing surveillance.

This information is collected by the Therapeutic Goods Administration (TGA) from three sources:

  • pharmaceutical companies (who are required to report side effects they become aware of)
  • health professionals
  • the public.

All of this information helps to provide a clearer picture about the severity and frequency of the medicine’s side effects. However, because the information is collected from the general population, without any comparison group, it is harder to be sure whether new side effects are really caused by the medicine, or by something else.

For example, suppose a new medicine was causing heart attacks at a rate of 3 per 5000 people and this wasn’t detected in clinical trials. Once the drug went on sale, imagine it was commonly used by people who already have a higher risk of heart attack, such as older smokers. If one of these people had a heart attack and was taking the new medicine, it would be difficult to say whether the drug was causing the heart attacks or it was something else. A single report of one person having a heart attack while on this medicine would not be enough to decide the cause, but if a larger number of reports were made the TGA would take a closer look at the safety of the medicine.

Reporting side effects

There are a number of ways you can report side effects to the Therapeutic Goods Administration. These include:

Each report that the TGA receives is collected in a national database of adverse events. ‘Adverse events’ includes both side effects and other problems that may occur while using a medicine which turn out not to be a medicine-related side effect.

The information is regularly analysed so that any potential safety concerns can be investigated in detail. If the TGA identifies a new safety concern such as a new side effect, it can take action to address it and make sure that health professionals and the public are aware of it.

Advising your health professional

Always tell your health professional if you think you are having a side effect from your medicine. They may report new or unusual medicine-related side effects they observe or that are reported to them by their patients to the Therapeutic Goods Administration (TGA). Your personal information will remain confidential and your privacy maintained.

Calling the Adverse Medicines Events (AME) Line (1300 134 237)

The AME Line is phone-in service that encourages members of the public to report and discuss side effects that might be related to their medicine. Medicine-related side effects are then reported to the Therapeutic Goods Administration (TGA) for assessment and contribute to national medicine safety efforts. Your personal information will remain confidential and your privacy maintained. Read more about the AME Line.

Reporting side effects directly to the TGA

You can report suspected side effects directly to the Therapeutic Goods Administration (TGA) via the TGA website.

For more information