Acute poisoning with the neonicotinoid insecticide imidacloprid in N-methyl pyrrolidone

Background: Imidacloprid [1-(6-chloro-3-pyridylmethyl)-N-nitroimidazolidin-2-ylideneamine, CAS 138261-41-3] belongs to a relatively new class of insecticidal chemistry, the chloronicotinyl neonicotinoid compounds. Animal studies indicate relatively low toxicity to mammals because they have resistant nicotinic receptor subtypes compared to insects, as well as protection of the central nervous system by the blood brain barrier. Despite wide usage, human exposure experience resulting in toxicity is quite limited. Case Report: Here, we report a case of acute ingestion of an insecticide formulation containing 9.7% imidacloprid, <2% surfactant, and the balance as solvent, N-methyl pyrrolidone. Clinical manifestation included drowsiness, disorientation, dizziness, oral and gastroesophageal erosions, hemorrhagic gastritis, productive cough, fever, leukocytosis, and hyperglycemia. The patient recovered without complication with supportive treatment and was discharged 4 days after ingestion. Follow-up barium upper gastrointestinal examination I month later was normal. Because moderate to high dose imidacloprid in animals causes central nervous system activation similar to nicotine, including tremors, impaired pupillary function, and hypothermia, it is unclear whether imidacloprid had a causal role in the patient's initial drowsiness and dizziness. It is more likely that the formulation ingredients, particularly N-methyl pyrrolidone, caused most of the clinical symptoms including minor central nervous system depression, gastrointestinal irritation, and hyperglycemia.