Methylene blue-A double-edged sword in the treatment of methemoglobinemia in a patient with emamectin benzoate poisoning: A case report

Abstract

Emamectin benzoate (EB), a widely used avermectin-derived pesticide, rarely causes mammalian toxicity butcan induce severe methemoglobinemia following acute exposure. We report a case detailing the management ofEB-induced methemoglobinemia, complicated by methylene blue-induced hemolytic anemia in a non-G6PD-deficientpatient. A 34-year-old male presented with altered sensorium, hypoxemia, and severe methemoglobinemia (63%)6 h post-ingestion of 15 mL EB (1.9%). While early intubation and targeted pharmacotherapy (methylene blue andVitamin C) successfully normalized his methemoglobin levels, his clinical course was complicated on day six bynon-G6PD-deficient hemolytic anemia (hemoglobin drop: 13.8–6.5 g/dL). The patient recovered fully followingsupportive therapy and red blood cell transfusion. This case demonstrates that while methylene blue effectively reversesEB-induced methemoglobinemia, it can precipitate severe, delayed hemolytic anemia even in G6PD-normal patients.This suggests a potential synergistic hematologic toxicity between EB and methylene blue. Clinicians should maintainprolonged vigilance for hemolysis and carefully weigh alternative therapies for methemoglobinemia