The scale consists of series of questions that will give the healthcare provider an idea about the likelihood of whether the ADR was a result of the drug itself, or some other factors behind the scene.
The Naranjo criteria classify the probability that an adverse event is related to drug therapy based on a list of weighted questions, which examine factors such as the temporal association of drug administration and event occurrence, alternative causes for the event, drug levels, dose-response relationships and previous patient experience with the medication. The ADR is assigned to a probability category from the total score as follows:
The Naranjo criteria doesn’t take into account drug-drug interactions. Drugs are evaluated individually for causality, and points deducted if another factor may have resulted in the adverse event, thereby weakening the causal association.