Naranjo adverse drug reaction probability scale
Questions	Yes	No	Do not know	Score
Are there previous conclusive reports on this reaction?	+ 1	0	0
Did the adverse events appear after the suspected drug was given?	+ 2	− 1	0
Did the adverse reaction improve when the drug was discontinued, or a specific antagonist was given?	+ 1	0	0
Did the adverse reaction appear when the drug was readministered?	+ 2	− 1	0
Are there alternative causes that could have caused the reaction?	− 1	+ 2	0
Did the reaction reappear when a placebo was given?	− 1	+ 1	0
Was the drug detected in any body fluid in toxic concentrations?	+ 1	0	0
Was the reaction more severe when the dose was increased, or less severe when the dose was decreased?	+ 1	0	0
Did the patient have a similar reaction to the same or similar drugs in any previous exposure?	+ 1	0	0
Was the adverse event confirmed by any objective evidence?	+ 1	0	0

Total score:

Scoring

≥ 9 = definite adverse drug reaction

5–8 = probable adverse drug reaction

1–4 = possible adverse drug reaction

0 = doubtful adverse drug reaction

Naranjo CA, Busto U, Sellers EM, Sandor P, Ruiz I, Roberts EA et al. (1981) A method for estimating the probability of adverse drug reactions. https://www.ncbi.nlm.nih.gov/pubmed/7249508