Pharmacovigilance: the basics

All of us will take medicines at some point in our lives. Pharmacovigilance is all about the safer and more effective use of medicines, for everyone. It covers everything from noticing, assessing, understanding, and managing the adverse effects of medicines to preventing those effects in both individuals and populations.

Medicines cure, but they can also harm

Medicines have brought enormous benefits, but no medicine is 100% safe for all people in all situations. While some medicines can cause severe or even fatal adverse drug reactions, most have predominantly beneficial effects for most people – even while they may cause occasional minor harm (such as a headache, rash, or tiredness).
Every time a treatment option is considered, the prescriber and patient must decide if the benefits are sufficient to accept the possibility of discomfort or harm, which may already be known and recorded on the patient leaflet. Sometimes unexpected minor or serious harm may occur. This is why watching and reporting are so important: the more we know about what patients have experienced, the better informed we are to prevent harm in the future. The risks of vaccines causing harm are much lower than those for medicines, but monitoring is still necessary.

"Telling your doctor or pharmacist about adverse effects will help make drug use safer for everyone."


You may wonder why medicines cause harm at all. Medicines are a powerful, usually chemical or biological invasion of the body; that is why they can cure diseases, but also why they sometimes cause damage.
We get to know about many of the benefits and harms that a medicine can cause when it is tested in clinical trials. However, these involve only from a few hundred up to a few thousand carefully selected people, so they do not represent the whole population of patients (maybe millions) who will eventually use the drug. It is only after the drug has been used by large numbers of patients over a longer period of time that more of its effects become clear, especially rare ones. Reporting rare effects is particularly important in characterising the safety profile of a drug.
It is also the case that people react differently to medicines, because everyone has different risk factors – relating to genetics, other diseases and medication, allergies, social conditions, psychology and so on. We need to know what it is that makes every patient vulnerable to harm; when harm occurs, it needs to be added to the body of knowledge that will influence how medicines are used in the future.


How do medicines cause harm?

How do we reduce the risk of harm from medicines?

Wise therapeutic decisions, which give patients the greatest benefits with the least risk, must be made jointly by health providers and patients.
A patient must understand, anticipate, and recognise the known negative side effects of a drug; there must be a plan for when they first appear, and agreed action taken. The first step is likely to be returning to report the problem to the prescriber.
Taking the drug as prescribed, finishing the course, avoiding interactions with other foods or drugs – in other words adherence to the prescribing guidelines – all help to reduce the possibility of harm.
Nevertheless, the risk of harm cannot be completely eliminated. Patients must be prepared for occasional mild adverse side effects and be alert if there is any indication at all of potentially more serious ones. In that case, urgent action may be necessary.


Watching for safer medicines

Understanding patients’ experiences of treatment, and especially the harm that they may suffer, is an important aspect of patient care and public health. Recognising and reporting adverse effects – as well as lack of effect and even unexpected benefits – will help to improve treatment and prevent harm for other patients in the future.
As patients, we can all report the effects of treatment to our doctor or pharmacist, especially harmful effects. When we tell them about a problem, they should discuss it with us, diagnose the cause of the problem, and agree with us what needs to be done. Action could include changing the dose or stopping the drug and trying an alternative.
Medicines may affect many aspects of patients’ lives, not only in relation to their specific impact on disease. Adverse effects, even mild ones, may negatively impact patients’ work or lifestyle (by making them drowsy and unable to drive, for example). Patients may assess benefit and harm in ways very different from professionals. Recording these aspects of therapy is critical to a full understanding of patients’ experiences, but is beyond the bounds of most current medical record-keeping or reporting.

The UMC glossary contains meanings and explanations of many words and phrases used in the field.

Last modified on: February 22, 2024