Unexpected adverse drug reaction

An unexpected adverse drug reaction (unexpected ADR) is an untoward reaction that is not consistent with the information provided in the product’s labeling or the investigator’s brochure. This means that the adverse reaction is not anticipated based on the known safety profile of the drug.

Definitions

ICH E6(R2)

1.60 Unexpected Adverse Drug Reaction:

An adverse reaction, the nature or severity of which is not consistent with the applicable product information (e.g., Investigator’s Brochure for an unapproved investigational product or package insert/summary of product characteristics for an approved product) .

Why it is unexpected

The term “unexpected” refers to the fact that drug reaction was not anticipated based on prior clinical experience, studies, or the drug’s labeling. This could occur due to:

• new or rare side effects that were not identified in previous clinical trials
• reactions that manifest in a different patient population or under different conditions than initially studied
• reactions that arise from long-term use or interactions with other drugs that were not previously documented

Difference between adverse event and adverse reaction

While an adverse event is any unfavorable medical occurrence, whether related to the drug or not, an adverse drug reaction is a specific event that is causally related to the use of the drug.

	Adverse event (AE)	Adverse drug reaction (ADR)
Definition	Any unfavorable or unintended medical occurrence in a clinical trial subject	An adverse event specifically related to the use of a drug
Relation to study drug	May or may not be related to study drug	Directly related to the drug’s use
Scope	Broader term, encompassing all negative outcomes observed in a clinical setting, regardless of causality	Narrower term, specifically focusing on harmful effects caused by the drug

See also

Another relevant pages

• Adverse drug reaction
• Adverse event
• Drug safety

External links

• ICH Guideline for Clinical Safety Data Management: Definitions and Standards for Expedited Reporting