A case of methanol intoxication caused by methomyl pesticide ingestion

When clinicians treat patients with pesticide poisoning, they often pay attention only to the chief toxic agent and ignore the toxicity of the pesticide's additives or solvents. Occasionally, however, a solvent (e.g. methanol) may itself be the cause of poisoning. We report a case of acute methanol intoxication that occurred after ingestion of a methomyl pesticide that contained methanol as an additive. A 49-year-old man was brought to the emergency department in an unconscious state after ingestion of 20 ml of a carbamate pesticide (chief ingredient: methomyl; active ingredient: methanol). Upon arrival, he was semicomatose and did not breathe spontaneously; however, his cholinesterase level was within normal limits and cholinergic symptoms were not observed. High anion gap metabolic acidosis was present. His blood ethanol level was 74.8 mg/dL. The urine methanol level was 55.60 mg/dL, and urine ethanol level was 22.0 mg/dL. He was treated with hemodialysis; subsequently, his metabolic acidosis resolved and he returned to normal mental status. We guessed that methanol, as the solvent of the methomyl, had produced the symptoms. When treating pesticide-poisoned patients, clinicians should identify the solvent used in the pesticide, because solvents such as methanol may exacerbate the symptoms of poisoned patients.