Naranjo ADR Probability Calculator
Naranjo ADR Probability Calculator
Structured decision support for estimating the likelihood that a drug caused an adverse reaction, using the 10‑item Naranjo algorithm. This tool supports documentation, auto‑scoring, and export. It does not replace clinical judgment.
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Total score
0
Auto‑calculated
Category
Doubtful
≥9 Definite; 5–8 Probable; 1–4 Possible; ≤0 Doubtful
Exposure → Onset
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Calculated from timestamps if provided
Questions (select the best answer)
1) Previous conclusive reports on this reaction?
Is the AE well‑documented for this drug/class (label or literature)?
2) Did the AE appear after the drug was given?
Temporal relationship: exposure precedes onset.
3) Did the AE improve on dechallenge or with a specific antagonist?
Clinical improvement after stopping the drug or giving an antidote.
4) Did the AE reappear on rechallenge?
Recurrence when the drug was re‑introduced.
5) Alternative causes likely?
Intercurrent disease, other drugs, exposure providing a competing explanation.
6) Did the AE reappear with placebo?
Recurrence with placebo suggests non‑drug cause.
7) Drug detected in toxic concentrations?
Therapeutic drug monitoring or levels indicating toxicity.
8) Dose–response: worse with higher dose or better with lower dose?
Severity tracks dose changes.
9) Similar reaction previously to same or similar drugs?
Past history with this drug/class.
10) Objective evidence confirming AE?
Labs, imaging, biopsy, challenge tests supporting diagnosis.
Doubtful
Derived from current inputs
Interpretation
Context
Case: —
Suspect drug: —
Assessor: —
Suspect drug: —
Assessor: —
Exposure → Onset: —
Concomitants: —
Concomitants: —
Event narrative
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