[Acute dapsone exposure and methemoglobinemia in children: treatment with multiple doses of activated charcoal with or without the administration of methylene blue]

OBJECTIVE: To study the changes in methemoglobinemia of 17 children admitted with acute exposure to dapsone complicated by a methemoglobin concentration greater than 20% of the total hemoglobin. The children were treated with multiple doses of activated charcoal with or without the administration of methylene blue.PATIENTS AND METHODS: Seventeen patients (ages 1-13 y, median 3 y), were admitted 1-72 h after the ingestion of 100-1200 mg (median 350 mg, 10 patients) or an unknown amount of dapsone (7 patients). The methemoglobin blood concentrations upon admission ranged from 23.5%-49.7% (median 37.8%), and the main clinical features were cyanosis (17), tachycardia (17), vomiting (11) and tachypnea (8). All of the children received multiple doses of activated charcoal orally or via nasogastric tube (1g/kg, 10% solution, 4-6 times/day, 3-16 doses with a median of 8 doses). Twelve of the 14 patients with methemoglobin levels greater than 30% were also treated with a single dose of methylene blue (1-2% solution, 1-2 mg/kg) infused IV over 5 min.RESULTS: There was a progressive decrease in the methemoglobin levels after the beginning of both treatments (multiple doses of activated charcoal alone or associated with methylene blue), and only one dose of methylene blue was necessary. There were no significant statistical differences between the results of the two treatments according to the time-course decrease in methemoglobinemia (p=0.49 Wilcoxon test).CONCLUSIONS: Multiple doses of activated charcoal given when methemoglobin levels were greater than 20% can be considered as a possible treatment for pediatric patients, with or without the administration of methylene blue, after acute dapsone exposure.