Table 2.
The Naranjo adverse drug reaction probability scale
| Question | Answer
|
|||
|---|---|---|---|---|
| Yes | No | Do not know | ||
| 1 | Are there previous conclusive reports on this reaction? | +1 | 0 | 0 |
| 2 | Did the adverse event appear after the suspected drug was administered? | +2 | –1 | 0 |
| 3 | Did the adverse event improve when the drug was discontinued or a specific antagonist was administered? | +1 | 0 | 0 |
| 4 | Did the adverse event reappear when the drug was readministered? | +2 | –1 | 0 |
| 5 | Are there alternative causes that could on their own have caused the reaction? | –1 | +2 | 0 |
| 6 | Did the reaction reappear when a placebo was given? | –1 | +1 | 0 |
| 7 | Was the drug detected in blood or other fluids in concentrations known to be toxic? | +1 | 0 | 0 |
| 8 | Was the reaction more severe when the dose was increased or less severe when the dose was decreased? | +1 | 0 | 0 |
| 9 | Did the patient have a similar reaction to the same or similar drugs in any previous exposure? | +1 | 0 | 0 |
| 10 | Was the adverse event confirmed by any objective evidence? | +1 | 0 | 0 |
| Total score | Interpretation: probability of an adverse drug reaction | |||
| ≥9 | Definite | |||
| 5–8 | Probable | |||
| 1–4 | Possible | |||
| ≤0 | Doubtful | |||
Note: Reproduced with permission from Naranjo CA, Busto U, Sellers EM, et al. A method for estimating the probability of adverse drug reactions. Clin Pharmacol Ther. 1981;30(2):239–245.16 © 1981 American Society for Clinical Pharmacology and Therapeutics.