Definition

A probability scale using 10 weighted questions to estimate the likelihood of an adverse drug reaction, producing scores categorized as definite, probable, possible, or doubtful.

Example

A case with positive dechallenge (+2), reasonable time sequence (+2), confirmed by rechallenge (+3), and no alternative explanation (+2) scores 9, indicating 'definite' causality.

Regulatory source

Naranjo et al. 1981, Clinical Pharmacology

Common mistakes

Mechanically applying scores without considering the clinical context. The algorithm is a guide, not a replacement for medical judgment.

Inspector question

Do you use the Naranjo algorithm? How do you handle cases where the algorithm score doesn't align with clinical judgment?

Related terms