Parathion intermediate syndrome

De Bleecker J, Willems J, Van Den Neucker K, et al. 1992. Prolonged toxicity with intermediate syndrome after combined parathion and methyl parathion poisoning. Clin Toxicol 30 333-345. 

Nisse K, Eorceville X, Cezard C, Ameri A, and Mathieu-Nolf M (1988) Intermediate syndrome with delayed distal polyneuropathy from ethyl parathion poisoning. Veterinary and Human Toxicology 40 349-352. 

Repeated or prolonged exposure to parathion can cause the same effects seen with acute exposures. In people working directly in the manufacture or application of parathion, impaired memory and concentration, disorientation, severe depressions, irritability, confusion, headache, speech difficulties, delayed reaction times, nightmares, and sleepwalking and drowsiness or insomnia have all been reported. Parathion cannot cause delayed neurotoxicity but has been reported to be associated with the intermediate syndrome. 

OP insecticide-induced intermediate syndrome (IMS) was reported for the first time in human patients in Sri Lanka in 1987 (Senanayake and Karalliede, 1987). Since then, this syndrome has been diagnosed in OP-poisoned patients in South Africa (1989), Turkey (1990), Belgium (1992), the United States (1992), Venezuela (1998), France (2000), and elsewhere. IMS is usually observed in individuals who have ingested a massive dose of an OP insecticide either accidentally or in a suicide attempt. IMS is clearly a separate clinical entity from acute toxicity and delayed neuropathy. A similar syndrome has also been observed in dogs and cats poisoned maliciously or accidentally with massive dosc.s of certain OPs. OPs that are known to cause IMS include bromophos, chlorpyrifos, diazinon, dicrotophos, dimethoatc, fenthion, malathion, merphos, methamidophos, methyl parathion, monocrotophos, omethoate, parathion, phosmet, and trichlorfon. These compounds and IMS are discussed further in Chapter 26. 

Nisse, P., Forceville, X., Cezard, C. C., Amcri, A., and Mathicu-Nolf, M. (1998). Intermediate syndrome with delayed di.stal polyneuropathy from ethyl parathion poisoning. Vet. Hum. Toxicol. 40, 166-168. 

Early high-toxicity pesticides such as TEPP and parathion have now fallen out of use. Organophosphorus pesticides (and in some cases other phosphate esters such as tricresyl phosphate) are now believed to produce several responses in humans. Acute symptoms can appear within hours of exposure, intermediate syndromes within days, and a delayed response which may take months or even years to develop. The latter is known as OP-induced neuropathy (OPIDN) and is difficult to treat and may be irreversible. 

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