Naranjo algorithm

The Naranjo Algorithm, also known as the Naranjo Scale or Naranjo Nomogram, is a methodological tool conceptualized by Naranjo and his colleagues. Its primary function is to assess the likelihood of an Adverse Drug Reaction (ADR) being attributable to a drug as opposed to other potential factors.<ref>Naranjo CA, Busto U, Sellers EM, et al. A method for estimating the probability of adverse drug reactions. Clin Pharmacol Ther 1981;30:239-45.</ref>

Purpose and Application

In clinical practice and research, distinguishing between genuine ADRs and symptoms stemming from other causes can be challenging. The Naranjo Algorithm facilitates this by providing a structured framework to:

• Gauge the probability of a drug causing an ADR
• Help healthcare professionals make informed decisions about medication safety
• Support authors in peer reviews by verifying the validity of conclusions concerning ADRs<ref>Agbabiaka TB, Savovic J, Ernst E. Methods for causality assessment of adverse drug reactions: a systematic review. Drug Saf 2008;31:21-37.</ref>

Questionnaire

The questionnaire comprises ten questions, each designed to elicit information relevant to the causative role of the drug in the observed ADR.

1. Previous Reports

Have there been previous conclusive reports on this reaction?

Yes (+1) | No (0) | Do not know/not done (0)

1. Adverse Event Post-Drug Administration

Did the adverse event appear after the suspected drug was administered?

Yes (+2) | No (-1) | Do not know/not done (0)

1. Improvement upon Discontinuation

Did the adverse reaction improve when the drug was discontinued or a specific antagonist administered?

Yes (+1) | No (0) | Do not know/not done (0)

1. Reaction on Re-administration

Did the adverse reaction appear when the drug was readministered?

Yes (+2) | No (-1) | Do not know/not done (0)

1. Alternative Causes

Could there be alternative causes for the reaction?

Yes (-1) | No (+2) | Do not know/not done (0)

1. Reaction to Placebo

Did the reaction reappear when a placebo was given?

Yes (-1) | No (+1) | Do not know/not done (0)

1. Toxic Concentrations

Was the drug detected in any body fluid in toxic concentrations?

Yes (+1) | No (0) | Do not know/not done (0)

1. Reaction Severity with Dose Changes

Was the reaction more severe with increased dose or less severe with decreased dose?

Yes (+1) | No (0) | Do not know/not done (0)

1. Previous Exposure

Did the patient have a similar reaction to the same/similar drugs in any previous exposure?

Yes (+1) | No (0) | Do not know/not done (0)

1. Objective Evidence

Was the adverse event confirmed by any objective evidence?

Yes (+1) | No (0) | Do not know/not done (0)

Scoring

Based on the cumulative score derived from the questionnaire:

• ≥ 9: Definite ADR
• 5-8: Probable ADR
• 1-4: Possible ADR
• 0: Doubtful ADR

Significance and Limitations

While the Naranjo Scale provides a systematic approach to evaluating ADRs, like any tool, it has limitations. The questionnaire relies heavily on the subjective assessment and knowledge of the evaluator. Consequently, it is crucial to apply the Naranjo Algorithm within its intended context, understanding its strengths and constraints.<ref>Ribeiro-Vaz I, Santos CC, Cruz-Correia R. A method and a computational tool to assess drug causality in adverse drug reactions: pilot study. Drugs Real World Outcomes. 2018;5(1):47-55.</ref>

References

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External links

• Naranjo algorithm
• Online calculator

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