Dichlorvos, neurotoxicity

The development of efficient means for prevention of neurotoxic action of OPC (TOCP, mipaphox, dichlorvos, DFP, etc.) of the delayed type (DNE) remains to be relevant. 

Most insecticides, especially the organophosphate group, cause neurotoxicity as their major mode of action. Assessment of the neurotoxicity includes neurochemical endpoints such as cholinesterase (including acetylcholinesterase, which is the major neurotransmitter in vertebrates such as fish, and other enzymes such as butyrylcholinesterase) inhibition and behavioral endpoints such as swimming speed [79]. Studies done in rats show the neurotoxic action of insecticides such as dimethoate, methyl parathion, dichlorvos, ethyl parathion or propoxur after a prolonged exposure [80,81]. 

Other anticholinesterases recently licensed in Europe include metrifonate. This is an irreversible organophosphorus inhibitor of acetylcholinesterase and is a pro-drug for dichlorvos. The development of metrifonate was delayed because some patients developed muscle weakness and a delayed neurotoxicity has been described for compounds that are chemically related to the drug. 

Neurotoxic chemicals and motor neuropathy Chlorpyrifos, dichlorvos (DDVP), EPN, n-hexane, 2-hexanone, lead, lead chromate, lead II thiocyanate, leptophos, methamidophos, mipafox, omethoate, parathion, trichlor-fon, trichloronate, triorthocresyl phosphate Neurotoxic chemicals and sensorimotor neuropathy acrylamide, allyl chloride, arsenic and compounds, arsenic trichloride, calcium arsenate, carbon disulfide, dichloroacetylene, ethylene oxide, gallium arsenide, lead arsenate, mercuric chloride, mercuric nitrate, mercurous nitrate, mercury, nitrous oxide, phenyl arsine oxide, thallium and soluble compounds, thallous nitrate... 

Delayed neurotoxicity results from degeneration of the axons followed by demyelination (14,15,23). Clinical manifestation includes sensory disturbances, ataxia, weakness, muscle twitching and, in severe cases, complete flaccid paralysis ( 15). A fair number of organophosphate compounds are capable of inducing delayed neurotoxicity. Of the 250 organophosphates (not all pesticides) tested for delayed neurotoxicity in chickens, 47% (117 chemicals) showed positive responses (23). Notable examples of pesticides which possess this neurotoxicity are leptophos, EPN, merphos, dichlorvos, and... 

Caroldi. S., and Lotti, M. (198J). Delayed neurotoxicity caused by a single massive do.se of dichlorvos to adult hens. Toxicol. Lett. 9, 157-159. 

Choudhary, S., and Gill, K. D, (2001). Protective effect of nimodipine on dichlorvos-induced delayed neurotoxicity in rat brain. Biochem Pharmacol. 62, 1265-1272. 

Wadia, R. S., Shinde, S. N., and Vaidya, S. (1985). Delayed neurotoxicity after an episode of poisoning with dichlorvos. Neurol. India 33,247-253-... 

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