ADR (Adverse Drug Reaction)
What is it?
An ADR is a harmful, unintended response to a medicine, taken at a normal dose, where there's a reasonable possibility the drug caused it. That last part is what separates it from a plain adverse event: an AE is anything untoward that happens to a patient regardless of suspected cause, while an ADR already carries at least a provisional causality judgment.
In practice, most incoming safety reports start life as adverse events. It's only once a reporter or an assessor has enough reason to suspect the drug is implicated, even loosely, that the case gets treated and coded as an ADR.
Where does this case land?
Adverse Event, ADR, and side effect aren't synonyms, they're nested scopes. Click a layer to see what actually separates them.
Click a layer to see its scopeAdverse Event (AE): anything untoward that happens to a patient on treatment, no suspicion of drug causation required.
Example: a patient on a new medicine reports nausea. Nobody yet knows if the drug is involved. That's enough to log it as an AE.
ADR: narrows that down to cases where there's a reasonable possibility the drug caused it, a provisional causality judgment, not a final one.
Example: that same nausea, once an assessor decides the timing and pharmacology make the drug a plausible cause, gets reclassified as an ADR.
Side effect: narrower still: an effect that's already known and listed for the drug, not a new finding.
Example: if nausea is already printed in the product label, this same case is just a known side effect showing up again, not new safety information.
Common Misconceptions
"AE, ADR, side effect: these are all just different ways of saying the same thing, right?"
They form a scale, not a synonym set. AE is the widest net, no suspicion of cause required. ADR narrows that to cases with a reasonable possibility of drug causation. Side effect narrows it further still, to effects that are already documented and expected.
