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Adverse drug reactions - Background information
What is an adverse drug reaction?
- An adverse drug reaction (ADR) is an unwanted or harmful reaction which occurs after administration of a drug or drugs and is suspected or known to be due to the drug(s) [MHRA, 2006a].
- The reaction predicts hazard from future administration and warrants prevention or specific treatment, or alteration of the dosage regimen, or withdrawal of the product [Edwards and Aronson, 2000; Aronson and Ferner, 2005].
- The reaction may be a known effect of the drug, or it may be new and previously unrecognized [MHRA, 2006a].
- There are other terms that should be distinguished:
- The terms 'adverse reaction' and 'adverse effect' are interchangeable but reflect different points of view: a drug has an adverse effect, whereas a person experiences an adverse reaction [Edwards and Aronson, 2000; Aronson and Ferner, 2005].
- These terms are preferred to other terms, such as 'toxic effect' or 'side effect', because they encompass all unwanted effects. They make no assumptions about mechanism, evoke no ambiguity, and avoid the risk of misclassification [Edwards and Aronson, 2000; Aronson and Ferner, 2005].
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