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Adverse drug reaction
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An adverse drug reaction is a harmful response that nobody intended. It shows up even when the drug is taken at normal doses, and it is causally linked to the drug: it comes from that medication, not from something else that happened at the same time.
These reactions fall into two types. Type A reactions arise from the drug's known pharmacological properties, meaning what it is already known to do, and they can happen to anyone if the dose is high enough. It is like a kitchen knife: if it cuts the person using it, that is explained by what a knife is. Type B reactions, on the other hand, cannot be predicted from those properties.
An adverse reaction can also come from an interaction, the drug's encounter with other medications, foods, beverages, supplements or a disease. And within type B are idiosyncratic reactions, which do not involve the immune system or inflammation. They may be due to a genetic abnormality or to an exaggerated sensitivity to low doses.
In brief
An adverse drug reaction is a harmful, unintended response to a drug, occurring at usual doses and causally linked to it.
They are classified as type A, which arise from known pharmacological properties and can occur in anyone at a high enough dose, and type B, which those properties do not predict.
Idiosyncratic reactions, type B reactions that are neither immune nor inflammatory, may stem from genetic abnormalities or exaggerated sensitivity to low doses; an interaction with other drugs, foods, beverages, supplements or diseases can cause adverse reactions.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingAdverse Drug Reactions, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated