Metoclopramide-induced methemoglobinemia in an adult

Methemoglobinemia is a condition characterized by increased level of methemoglobin in the erythrocytes and brownish cyanosis. Acquired methemoglobinemia is diagnosed by elevated methemoglobin with normal hemoglobin electrophoresis and normal NADH cytochrome b5 reductase. We report a patient who developed lethargy, confusion, and cyanosis during post-operative period. He had arterial methemoglobin level of 40.6% and oxygen saturation of 59%. No other cause could be found for his methemoglobinemia other than metoclopramide, even though it is rarely reported to cause methemoglobinemia in adults compared to infants. He had an excellent clinical response to treatment with methylene blue with which his clinical symptoms improved and the methemoglobin level returned to normal within 24 hours. Here we discuss the clinical features, diagnosis, and treatment of acquired methemoglobinemia induced by metoclopramide.