Table 1.

Naranjo Scale of causality

Question	Yes	No	Do not know or not done	Case
Are there previous conclusive reports on this reaction?	+1	0	0	+1
Did the adverse event appear after the suspected drug was given?	+2	−1	0	+2
Did the adverse reaction improve when the drug was discontinued or a specific antagonist was given?	+1	0	0	+1
Did the adverse reaction appear when the drug was readministered?	+2	−1	0	0 (not done)
Are there alternative causes that could have caused the reaction?	−1	+2	0	0 (investigation not done)
Did the reaction reappear when a placebo was given?	−1	+1	0	0 (not done)
Was the drug detected in any body fluid in toxic concentrations?	+1	0	0	0 (not done)
Was the reaction more severe when the dose was increased, or less severe when the dose was decreased?	+1	0	0	+1
Did the patient have a similar reaction to the same or similar drugs in any previous exposure?	+1	0	0	0 (no known history)
Total score 5–8: probable drug reaction				5

The scale is asfollows: >9 definite, 5–8 probable, 1–4 possible, <0 doubtful.