Table 1.
Naranjo ADR probability scale—items and score
| Question | Yes | No | Don’t know |
|---|---|---|---|
| Are there previous conclusion reports on this reaction? | +1 | 0 | 0 |
| Did the adverse event appear after the suspect drug was administered? | +2 | –1 | 0 |
| Did the AR improve when the drug was discontinued or a specific antagonist was administered? | +1 | 0 | 0 |
| Did the AR reappear when drug was re-administered? | +2 | –1 | 0 |
| Are there alternate causes [other than the drug] that could solely have caused the reaction? | –1 | +2 | 0 |
| Did the reaction reappear when a placebo was given? | –1 | +1 | 0 |
| Was the drug detected in the blood [or other fluids] in a concentration known to be toxic? | +1 | 0 | 0 |
| Was the reaction more severe when the dose was increased or less severe when the dose was decreased? | +1 | 0 | 0 |
| Did the patient have a similar reaction to the same or similar drugs in any previous exposure? | +1 | 0 | 0 |
| Was the adverse event confirmed by objective evidence? | +1 | 0 | 0 |
Scoring for Naranjo algorithm: >9 = definite ADR; 5–8 = probable ADR; 1–4 = possible ADR; 0 = doubtful ADR.