Organophosphate poisonings with parathion and dimethoate

Organophosphate toxicity is the leading cause of morbidity and death in poisoning by insecticides. The clinical symptoms of pesticide toxicity range from the classic cholinergic syndrome to flaccid paralysis and intractable seizures. The mainstays of therapy are atropine, oximes, benzodiazepines and supportive care. The toxicokinetics vary not only with the extent of exposure, but also with the chemical structure of the agent.

We report two cases of poisoning with parathion-ethyl and dimethoate. The patients developed a cholinergic syndrome immediately, accompanied by bradycardia and hypotension.

The patients were admitted to the intensive care unit (ICU) a few hours after ingestion. Atropine was administered according to the cholinergic symptoms. The patients recovered in the ICU after 10-12 days and were discharged after 3 and 4 weeks.

Organophosphate blood and urine levels were determined on admission and during hospitalisation. The pesticides were rapidly distributed and slow elimination rate of the poisons was documented. In the case of parathion-ethyl the distribution half-life estimated was t(1/2alpha) = 3.1h while the terminal half-life was t(1/2beta) = 17.9 h. Using a one-compartment model for dimethoate the elimination half-life was t(1/2beta) = 30.4 h in plasma and 23.8 h in urine. The serum pseudo-cholinesterase activity was below the limit of detection at admission and recovered during the following 3weeks.