A rare case of emamectin benzoate poisoning causing methemoglobinemia

Introduction: Emamectin Benzoate (4’-deoxy-4’-epi-methyl-amino Benzoate ), widely used as a broad-spectrum insecticide has a significant human safety margin. Methemoglobinemia from toxin exposure is a rare presentation of its poisoning. Due to their easy accessibility globally, agricultural insecticides have been utilized for self-poisoning on a regular basis. However, methemoglobinemia resulting from its toxic exposure is a rare occurrence. Case presentation: A 49-year-old farmer presented with altered mental status and difficulty in breathing 6 hours after ingesting an unknown substance which was later identified as Emamectin Benzoate at Government Stanley Medical College and Hospital, Chennai, Tamil Nadu, India, in September 2024. On admission the patient presented with hypoxemia, cyanosis and a “saturation gap”, with a co-oximetric methemoglobin level of 48%. The patient was treated with 0.1% methylene blue intravenously (IV) at a dose of 1 mg/kg body weight (total 50 mg) diluted in 50 mL of 5% dextrose over five minutes and also received 1 g intravenous vitamin C three times daily and N-acetylcysteine 1.2 gm for the methemoglobinemia. Despite the initial methylene blue treatment, his clinical status remained unchanged, so a second dose of methylene blue (50 mg) was administered an hour later. His clinical condition improved within 48 hours of treatment and was discharged on the fifth day.Discussion: Acquired methemoglobinemia can be due to substances like local anesthetic, dapsone, amyl nitrate, quinones, sulphonamides and rarely due to insecticides. In this context, Emamectin Benzoate compound caused methemoglobinemia after ingestion.Conclusion: Although rare, methemoglobinemia following pesticide ingestion can be fatal. It should be considered in cases of refractory hypoxemia and a "saturation gap." High clinical suspicion and appropriate management are key to improving patient outcomes.