Failure of Methylene Blue Treatment in Toxic Methemoglobinemia

A patient who ingested an aniline-containing material developed severe methemoglobinemia. The usual beneficial response from administering methylene blue was not obtained, and within 24 hours a marked hemolytic episode occurred. The patient was found to be glucose-6-phosphate dehydrogenase-deficient and was therefore unable to utilize methylene blue in the NADPH-dependent reduction of methemoglobin. The possible role of methylene blue in precipitating the hemolysis is also discussed.