Metronidazole-induced fixed drug eruption

A 67-year-old man presented with a history of an itchy, erythematous oval lesion over the right calf (figure 1). He was prescribed metronidazole for dysentery 1 day earlier. He mentioned history of a similar eruptive lesion in the same location, after he was prescribed metronidazole for an episode of diarrhoea about 4 months previously. At that time, the lesion appeared after 3 days of treatment. It was itchy and it healed after stopping the drug leaving a residual hyperpigmentation. Hence, we suspected it to be fixed drug eruption (FDE) due to metronidazole. As oral challenge test is risky and patch test is not available in our clinic, we assessed a causal relation between the drug and the adverse drug reaction (ADR) using Naranjo et al …