Table 2 Naranjo causality scale for adverse drug reactions

Question/ Scoring Yes/No/Do not know or unavailable	Case 1	Case 2	Case 3
1. Are there previous conclusive reports on this reaction?1/0/0	1	1	1
2. Did the adverse event appear after the suspected drug was given? 2/-1/0	2	2	2
3. Did the adverse reaction improve when the drug was discontinued or a specific antagonist was given? 1/0/0	1	1	1
4. Did the adverse reaction appear when the drug was readministered? 2/-1/0	0	0	0
5. Are there alternative causes that could have caused the reaction? -1/2/0	0	0	0
6. Did the reaction reappear when a placebo was given?-1/1/0	0	0	0
7. Was the drug detected in any body fluid in toxic concentrations? 1/0/0	1	0	0
8. Was the reaction more severe when the dose was increased/increasing, or less severe when the dose was decreased? 1/0/0	0	1	1
9. Did the patient have a similar reaction to the same or similar drugs in any previous exposure? 1/0/0	0	0	0
Total	5	5	5

Scoring > 9 = definite adverse drug reaction (ADR) 5-8 = probable ADR 1-4 = possible ADR 0 = doubtful ADR