Adverse drug reactions

Adverse drug reactions

There are several terms commonly used to describe adverse effects of drug therapy: 

  • An adverse drug reaction (ADR) is an unwanted or harmful reaction experienced following the administration of a drug or combination of drugs under normal conditions of use and is suspected to be related to the drug. An ADR will usually require the drug to be discontinued or the dose reduced.
  • An adverse event is harm that occurs while a patient is taking a drug, irrespective of whether the drug is suspected to be the cause. 
  • A side-effect is any effect caused by a drug other than the intended therapeutic effect, whether beneficial, neutral or harmful. The term ‘side-effect’ is often used interchangeably with ‘ADR’ although the former usually implies an effect that is less harmful, predictable and may not even require discontinuation of therapy (e.g. ankle oedema with vasodilators).  
  • Drug toxicity describes adverse effects of a drug that occur because the dose or plasma concentration has risen above the therapeutic range, either unintentionally or intentionally (drug overdose).
  • Drug abuse is the misuse of recreational or therapeutic drugs that may lead to addiction or dependence, serious physiological injury (such as damage to kidneys, liver, heart), psychological harm (abnormal behavior patterns, hallucinations, memory loss), or death.


Adverse drug reactions - basic principles

Adverse drug reactions - categorisation

Adverse drug reactions - drug allergy

Adverse drug reactions - diagnosis and management

Adverse drug reactions - avoiding adverse drug reactions

Adverse drug reactions - pharmacovigilance