Metformin-Induced Generalized Bullous Fixed-Drug Eruption with a Positive Dechallenge-Rechallenge Test: A Case Report and Literature Review

Table 1

The Naranjo algorithm for adverse drug reaction for a patient with metformin-induced fixed-drug eruption.

Questions	Yes	No	Do not know	Score
(1) Are there previous conclusive reports on this reaction?	+1	0	0	+1
(2) Did the adverse event appear after the suspected drug was administered?	+2	−1	0	+2
(3) Did the adverse event improve when the drug was discontinued or a specific antagonist was administered?	+1	0	0	+1
(4) Did the adverse event reappear when the drug was readministered?	+2	−1	0	+2
(5) Are there alternative causes that could on their own have caused the reaction?	−1	+2	0	+2
(6) Did the reaction reappear when a placebo was given?	−1	+1	0	0 (do not know)
(7) Was the drug detected in blood or other fluids in concentrations known to be toxic?	+1	0	0	0 (do not know)
(8) Was the reaction more severe when the dose was increased or less severe when the dose was decreased?	+1	0	0	0 (do not know)
(9) Did the patient have a similar reaction to the same or similar drugs in any previous exposure?	+1	0	0	+1
(10) Was the adverse event confirmed by any objective evidence?	+1	0	0	+1
	Total score: 10

Note. Naranjo Adverse Drug Reaction Probability Scale: ≥9 = definite adverse drug reaction; 5–8 = probable adverse drug reaction; 1–4 = possible adverse drug reaction; 0 = doubtful adverse drug reaction.