Metformin-Induced Fixed-Drug Eruption Confirmed by Multiple Exposures

A fixed-drug eruption (FDE) is a reaction characterized by cutaneous lesions that appear due to exposure to a particular drug. Barbiturates, carbamazepine, sulfamethoxazole, and tetracyclines have all been associated with causation of FDEs. Although these drugs are more commonly associated with FDEs, any introduction of a medication has the potential to result in a FDE. Metformin, a commonly used medication to improve glycemic control, has been reported to cause dermatologic reactions in some case reports, but only a single previously documented case report discusses the potential of metformin-associated FDE.

We describe a 56-year-old woman who developed a FDE with multiple exposures to metformin. Upon each exposure, small, round, erythematic lesions developed on the palms of the hands and soles of the feet; these lesions resolved each time after discontinuation of metformin. According to the Naranjo scale, there is a definite association between metformin and FDE in this case (score of 8).

This report contributes to the limited documented literature on metformin-induced FDE. Clinicians should be made aware of possible FDEs associated with this commonly used medication.