Human Pesticide Poisonings by a Fat-Soluble Organophosphate Insecticide

Abstract

In five cases of dichlofenthion poisoning due to suicidal ingestions, unusual toxicologic features were encountered. Initial symptoms were mild or delayed and severe cholinergic crises did not appear until 40 to 48 hours after ingestion. Two patients died, and in the three survivors, cholinesterase symptoms persisted for five to 48 days. An almost total inhibiton of both cholinesterase enzymes continued in one patient for 66 days, and prolonged antidotal therapy was required. Residues of the intact pesticide were detected in fat after 54 days in one patient, and in the blood for 75 days in another patient. The partition coefficient of dichlofenthion in fat was 20 times greater than parathion, and exceeded only by leptophos. Considering the chemical and toxicologic properties of this compound, we postulated that the mechanism of protracted intoxication is a slow release from adipose reservoirs.

Organophosphate and Carbamate Poisoning

“…22,23 Highly lipophilic agents cause protracted toxicity. 24,25 Redistribution of lipid soluble OPs from fat stores can "repoison" a patient.…”

Respiratory Complications of Organophosphorus Nerve Agent and Insecticide Poisoning. Implications for Respiratory and Critical Care

“…They can also cause recurrent cholinergic features days to weeks after poisoning, perhaps as fat stores are metabolized and OP is released. In a case series of five dichlofenthion-poisoned patients, one apparently stable patient developed sudden fatal cholinergic respiratory toxicity 60 hours after exposure, a second patient decompensated after 40 hours and needed resuscitation, and a third patient required atropine for 47 days to prevent recurrent cholinergic toxicity (83). Such recurrent effects are likely to explain the delayed encephalopathy and coma reported 4 to 7 days after admission for a small case series of patients poisoned by fat-soluble OP insecticides (84).…”

“…Very fat-soluble OP insecticides, such as dichlofenthion (83) and fenthion (20), cause delayed onset cholinergic poisoning, usually more than 24 to 48 hours after exposure. They can also cause recurrent cholinergic features days to weeks after poisoning, perhaps as fat stores are metabolized and OP is released.…”

Some Physical Factors in Toxicological Assessment Tests

“…Further proof of the relation of partition coefficient indicate accumulation and potential toxicity was found with dichlofenthion and leptophos. Here the individual had a single oral exposure but symptoms of intoxication and high residue levels upon biopsy were found for 30 + days following the exposure (15). Leptophos, of course, has a relatively low acute toxicity in short-term tests but has been demonstrated to be neurotoxic as a result of its accumulation and persistence.…”