Adverse drug reaction (ADR) Article 1 of Directive 2001/83/EC as amended defines an adverse drug reaction as "a response to a medicinal product which is noxious and unintended". An ADR is also known as a side effect.
Benefit-risk balance The weighing of the benefits (positive effects) of a medicine against its risks (adverse reactions). Sometimes known as benefit-risk ratio, the benefit-risk balance must be considered favourable for a medicine to be authorised. The benefits and risks of medicines are continuously monitored to confirm that the benefits are greater than the risks.
European Economic Area (EEA) Established on 1 January 1994 following an agreement between the member states of the European Free Trade Association (EFTA) and the European Community, later the European Union (EU). Specifically, it allows Iceland, Liechtenstein and Norway to participate in the EU's Internal Market without a conventional EU membership. In exchange, they are obliged to adopt all EU legislation related to the single market, except laws on agriculture and fisheries. One EFTA member, Switzerland, has not joined the EEA.
Effectiveness The ability of a medicine to produce the desired therapeutic effect when used in real-life conditions.
Efficacy The ability of a medicine to produce the desired therapeutic effect under ideal conditions (usually in a clinical-trial setting).
Epidemiology The study of the distribution and determinants of diseases in populations. Epidemiological studies help to inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventative medicine. (See Pharmacoepidemiology.)
EudraVigilance EudraVigilance is a system designed for collecting reports of suspected side effects. These reports are used for evaluating the benefits and risks of medicines during their development and monitoring their safety following their authorisation in the European Economic Area (EEA). The system, managed by the European Medicines Agency on behalf of the European Union (EU) regulatory network, provides a data-processing network that links the Agency with all national medicines regulatory authorities in the EEA and with pharmaceutical companies (known as marketing-authorisation holders). EudraVigilance contains reports of suspected adverse drug reactions that are submitted, in compliance with EU legislation, either by the national regulatory authority of the country where the suspected reaction occurred, or directly by marketing-authorisation holders.
National medicines regulatory authority The authority in each country responsible for regulation of medicines in their territory. See the list of national medicines regulatory authorities in the EEA.
Pharmacoepidemiology The branch of epidemiology concerned with the study of the use and effects of medicines in large numbers of people.

Defined as the science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other drug-related problem. The name is derived from the words pharmaco (Greek for 'medicine') and vigilantia (Latin for 'vigilance, watchfulness').

In line with this general definition, underlying objectives of pharmacovigilance in accordance with the applicable EU legislation are:

  • preventing harm from adverse reactions in humans arising from the use of authorised medicinal products within or outside the terms of marketing authorisation or from occupational exposure; and
  • promoting the safe and effective use of medicinal products, in particular through providing timely information about the safety of medicinal products to patients, healthcare professionals and the public.

Pharmacovigilance is therefore an activity contributing to the protection of patients’ and public health.


Information which suggests a new possible link or a new aspect of a known link between a medicine and a side effect that requires further investigation.

The Commission Implementing Regulation (EU) 520/2012 defines a signal as information arising from one or multiple sources, including observations and experiments, which suggests a new potentially causal association, or a new aspect of a known association between an intervention and an event or set of related events, either adverse or beneficial, that is judged to be of sufficient likelihood to justify verificatory action.

Spontaneous report of a side effect Spontaneous reports are unsolicited reports by healthcare professionals or patients and do not derive from a study or any organised data-collection scheme (e.g. systematic collection of data as part of a patient survey).