Difference of the clinical course and outcome between dapsone-induced methemoglobinemia and other toxic-agent-induced methemoglobinemia.

CONTEXT: Acquired methemoglobinemia is a potentially fatal condition that leads to tissue hypoxia. Although the clinical features of methemoglobinemia depend on the methemoglobin levels, the clinical course would differ depending on the causative agents.

OBJECTIVE: We attempted to clarify this issue by comparing the clinical course of methemoglobinemia caused by dapsone and that caused by other toxic agents.

MATERIALS AND METHODS: A retrospective case-control study was performed. All patients with methemoglobinemia and who were admitted to the emergency department (ED) of our hospital from 1 January 2002 to 31 December 2014 were included.

RESULTS: Of the 34 patients with methemoglobinemia, 15 ingested dapsone (14 with acute overdose and one with chronic therapeutic use) and 19 had been exposed to other toxic agents, such as sodium nitrites, indoxacarb, primaquine, and lidocaine. The clinical characteristics and the course of dapsone-induced and other toxic-agent-induced methemoglobinemia were compared. There was no significant difference in clinical presentation and methemoglobin level (38.5% vs. 35.0%, p = 0.456) upon their ED arrival between the two groups. However, the methemoglobin level after use of methylene blue and the total dose of methylene blue were higher in patients with dapsone-induced methemoglobinemia than in those with other agent-induced methemoglobinemia (11.9% vs. 1.7%, p = 0.001, 455 mg vs. 144 mg, p = 0.006). The majority of dapsone-induced methemoglobinemia (93.3%) required more than 72 h for normalization of the methemoglobin level, despite the use of methylene blue. Five of the study patients died due to multiorgan failure, and all of whom were inpatients with dapsone-induced methemoglobinemia.

CONCLUSION: The clinical course of dapsone-induced methemoglobinemia was worse than that of other toxic-agent-induced methemoglobinemia despite no significant difference in their initial clinical presentation. Continuous treatment with serial monitoring of the serum methemoglobin is necessary for patients with dapsone-induced methemoglobinemia.