Challenge–dechallenge–rechallenge (CDR) is a medical testing protocol in which a medicine or drug is administered, withdrawn, then re-administered, while being monitored for adverse effects at each stage.
CDR is one means of establishing the validity and benefits of medication in treating specific conditions[1] as well as any adverse drug reactions.
The Food and Drug Administration of the United States lists positive dechallenge reactions (an adverse event which disappears on withdrawal of the medication) as well as negative (an adverse event which continues after withdrawal), as well as positive rechallenge (symptoms re-occurring on re-administration) and negative rechallenge (failure of a symptom to re-occur after re-administration).
[5] In addition to suicidality, akathisia is a reaction to medication which is suggested as amenable to a CDR protocol.
[6][7] Clinical trials using a CDR protocol are also reported for clinicians attempting to assess the effects of a medication on patients.