A “response to a drug which is noxious and unintended and which occurs at doses normally used in man for prophylaxis, diagnosis, or therapy of disease or for the modification of physiological function.”
Causal link between drug and ADR.
Harm directly caused by the drug at normal doses, during normal use.
- Predictable ADRs: 70-80%
- Usually dose-related and generally preventable
- Unpredictable ADRs: 20-30%
- Hypersensitivity: Mediated by immune response
- Idiosyncratic: Abnormal reactivity to a chemical that is peculiar to a given individual. Extreme sensitivity to low doses or insensitivity to high doses. Could also be paradoxical response (not expected reaction).