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15–2: Appendix 15–2 Naranjo Algorithm

Naranjo Algorithm

∗Naranjo CA, Busto U, Sellers EM, Sandor P, Ruiz I, Roberts EA, et al. A method of estimating the probability of adverse drug reactions. Clin Pharmacol Ther. 1981;30(2):239-45.

To assess the adverse drug reaction, please answer the following questionnaire and give the pertinent score.

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Yes No Don't Know Score
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 reaction improve when the drug was discontinued or a specific antagonist was administered? +1 0 0
4. Did the adverse reaction reappear when the drug was readministered? +2 −1 0
5. Are there alternative causes (other than the drug) 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 the 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_____
Score Interpretation

___Definite: ≥ 9

___Probable: 5 to 8

___Possible: 1 to 4

___Doubtful: ≤ 0

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