Permethrin emulsion ingestion: clinical manifestations and clearance of isomers

Oral intoxication with permethrin, an insecticide which prolongs axonal sodium channel depolarization, has not been documented in humans. We treated a 59-year-old man who drank approximately 600 mL of 20% permethrin emulsion in a suicide attempt.

Sequential blood samples were obtained to determine permethrin isomer levels using high-performance liquid chromatography.

Vomiting and diarrhea occurred after ingestion. On admission, loss of consciousness and metabolic acidosis were observed. On regaining consciousness, the patient complained of a burning sensation in the oral cavity. He received fluid therapy after gastric lavage and recovered without severe complications. Apart from initially impaired consciousness, no clinical neurotoxicity such as tremor, hyperexcitation, ataxia, convulsions, or paralysis occurred, though these have been reported in permethrin-intoxicated animals. Serum permethrin concentrations peaked 3-4 hours after ingestion at 868 ng/mL. Clearance of trans permethrin was more rapid than that of cis permethrin.

The unequal clearance of permethrin isomers paralleled findings in animal experiments. Vomiting and diarrhea probably limited absorption in the present case, resulting in a peak serum concentration and a degree of neurotoxicity far less than those seen in animals.