Medical Terms & Explanations 101 x Adverse Drug Reactions

What are Adverse Drug Reactions (ADR)?



As defined by the European Medicines Agency (EMA) adverse drug reactions (ADR) are noxious and unintended responses to a medicine.[1] These, colloquially called, side effects can be caused by any pharmacologically active drug, even when used as intended. 

In contrast, side effects caused by excessive use (intended or unintended) of the drugs are referred to as toxicity.

When drugs are prescribed by healthcare professionals, a risk-benefit assessment is required, as all drugs can theoretically cause ADRs.[2] For this reason, patients must be aware of the risks before use and must be informed accordingly.

How can ADRs occur?

Often, ADRs result from low selectivity of active ingredients. Selectivity generally describes how many different structures or tissues an active ingredient binds to.[3] The higher the selectivity, the fewer structures are bound that can potentially cause ADRs.

Another resulting reason is the different patient populations. The studies (randomized controlled trials)  that drugs must undergo before they are approved for marketing often have high inclusion criteria, which excludes relevant target groups. In very old or pregnant people, for example, these drugs can then cause ADRs, which could not be found in the pre-marketing RCT-studies due to high inclusion criteria.

Where can I find relevant information?

Relevant information can be found in the package insert, the drug information leaflet or web platforms such as EudraVigilance or ImpactMonitor. This information on adverse drug reactions comes from the above-mentioned studies, from in-use data collection, or from spontaneous reports as a result of real-world-evidence.

Importance of reporting ADRs.

Doctors, pharmacists, manufacturers, and patients are thus highly encouraged to cooperate in the detection of adverse drug reactions.[4] This sustainably increases patient and drug safety. Especially in the case of new drugs or so-called orphan drugs for rare diseases, which often only have conditional marketing authorization, the reporting of adverse drug reactions is absolutely necessary if not required by law.

And this is exactly where XO Life comes into play, because  such reports can easily and securely be recorded via XO Life’s ImpactMonitor.


[1] European Medicines Agency. Adverse drug reaction. Last accessed: 15.03.2021

[2] Smith Marsh E. Daphne. 2018. PharmD. BC-ADM. CDE. College of Pharmacy. University of Illinois at Chicago.ünschte-arzneimittelwirkungen/das-nutzen-risiko-verhältnis-von-medikamenten Last accessed: 15.03.2021

[3]Urban JD et al. Functional selectivity and classical concepts of quantitative pharmacology. J Pharmacol Exp Ther. 2007. 320(1) p. 1-13.

[4] Barry, A. R., Koshman, S. L., & Pearson, G. J. (2014). Adverse drug reactions: The importance of maintaining pharmacovigilance. Canadian pharmacists journal : CPJ = Revue des pharmaciens du Canada : RPC, 147(4), 233–238. misunderstanding randomized controlled trials. Vol 210. p.  2-21. 

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