What are Adverse Drug Reactions

Adverse reactions to drugs are common. Only some are true allergic reactions. An adverse drug reaction is any response to a drug that is unwanted and unintended.

In many countries they are a frequent cause of hospitalisation and mortality. Sometimes the reactions are known side-effects of the drug, but some may be unrecognized.

Adverse drug reactions occur at the usual, or intended dose of the drug. Examples include:

  • A predictable side-effect from the action of the drug, just more than usually seen (e.g. getting more drowsy than most people after taking powerful painkillers).
  • A rare, unexpected reaction that isn’t part of the drug’s usual mechanism (e.g. allergy or anaphylaxis).
  • A chronic reaction only seen after prolonged exposure to a drug.
  • A delayed reaction that occurs some time after a drug has been ceased.
  • Reactions due to withdrawal that happen immediately when certain drugs are ceased.

Adverse drug reactions, including allergic reactions to medications, can be investigated at Queensland Anaesthetic Reaction Clinic. Typically they would require a consultation first, and then a decision about what investigations, if any, are needed to identify the reaction and find a solution. Allergic reactions to medications might require allergy testing (skin pricks or skin injections) to prove. Other adverse drug reactions may require other investigations, or sometimes only expert advice in the form of a letter to prevent the reaction recurring.

Adverse Drug Reactions