Agent Name


CAS Number




Major Category



Aimco systox; Demeton-S methyl sulfoxide; Demeton-S-methyl sulfoxid [German]; Demeton-S-methyl sulfoxide; Demeton-S-methyl-sulfoxid [German]; Demeton-methyl sulphoxide; Dimethyl S-(2-eththionylethyl) thiophosphate; ENT 24,964; Ethanethiol, 2-(ethylsulfinyl)-, S-ester with O,O-dimethyl phosphorothioate; Isomethylsystox sulfoxide; Metaisosystox sulfoxide; Metaisosystoxsulfoxide; Metasystemox; Metasystemox R; Metasystox-R; Metasytox R; Methyl oxydemeton S; Metilmercaptofosoksid (USSR); O,O-Dimethyl S-(2-(ethylsufinyl)ethyl) thiophosphate; O,O-Dimethyl S-(2-(ethylsulfinyl)ethyl) monothiophosphate; O,O-Dimethyl S-(2-(ethylsulfinyl)ethyl) phosphorothioate; O,O-Dimethyl S-(2-eththionylethyl) phosphorothioate; O,O-Dimethyl S-(2-ethylsulfinyl)ethyl thiophosphate; O,O-Dimethyl S-ethylsulphinylethyl phosphorothiolate; O,O-Dimethyl-S-(2-aethylsulfinyl-aethyl)-thiolphosphat [German]; O,O-Dimethyl-S-(2-ethylsulfinyl-ethyl)-monothiofosfaat [Dutch]; O,O-Dimethyl-S-(3-oxo-3-thia-pentyl)-monothiophosphat [German]; O,O-Dimetil-S-(2-etil-solfinil-etil)-monotiofosfato [Italian]; Oxydemeton-methyl; Oxydemeton-metile [Italian]; Oxydemetonmethyl; Phosphorothioic acid, O,O-dimethyl S-(2-(ethylsulfinyl)ethyl) ester; Phosphorothioic acid, S-(2-(ethylsulfinyl)ethyl) O,O-dimethyl ester; R 2170; S-(2-(Ethylsulfinyl)ethyl) O,O-dimethl phosphorothioate; S-(2-(Ethylsulfinyl)ethyl) O,O-dimethyl phosphorothioate; S-2-Ethylsulphinylethyl O,O-dimethyl phosphorothioate; Thiophosphate de O,O-dimethyle et de S-2-ethylsulfinylethyle [French]; S-(2-(Ethylsulfinyl)ethyl) O,O-dimethyl ester phosphorothioic acid; [ChemIDplus] UN2784


Organophosphate Insecticides


Colorless or yellow liquid; [HSDB] Clear amber liquid; [CAMEO]


Used as systemic insecticide and acaricide for cotton, vegetables, fruits, and field crops; [HSDB]


A cholinesterase inhibitor; Can be absorbed through skin; [CAMEO] A woman who was five months pregnant attempted suicide by ingestion and was hospitalized with symptoms including miosis, respiratory distress, muscular fasciculations, and coma (12 hours after admittance); Blood cholinesterase was reduced by 90%; The remainder of her pregnancy was without incident, and the babys neurological exams at birth and 8 days later were normal; [HSDB] Occupational exposure less likely to be symptomatic or require hospitalization than exposure to other cholinesterase inhibitors; [Reference #1] The average of two baseline respective cholinesterase activity determinations three days apart, with no exposures to enzyme inhibiting pesticides for at least 30 days, is recommended for each worker prior to exposure to cholinesterase inhibitors because of large inter-individual differences in published baseline values. To be established at least once a year. Removal from workplace exposures is recommended until the cholinesterase activity returns to within 20% of baseline. [TLVs and BEIs]


Banned in the EU for use as pesticide for plant protection; [eChemPortal: ESIS] Restricted use pesticide (RUP); [Reference #1]

Reference Link

EPA Pesticide Chemical Search

Exposure Assessment

Acetylcholinesterase activity in red blood cells = 70% of individual's baseline; Butylcholinesterase activity in serum or plasma = 60% of individual's baseline; Sample at end of shift; [TLVs and BEIs]

Vapor Pressure

2.85E-5 mm Hg

Lethal Concentration

LC50 (rat) = 427 mg/m3/1h

Explanatory Notes

The Guide in the Emergency Response Guidebook is for "Organophosphorus pesticide, liquid, flammable, toxic."

Reference Link

INCHEM JMPR: Oxydemeton-methyl - 2002

Adverse Effects
Other Poison


Links to Other NLM Databases
Health Studies

Human Health Effects from Hazardous Substances Data Bank:

Toxicity Information


Chemical Information

Search ChemIDplus

Biomedical References

Search PubMed

Related Information in HazMap

Occupational diseases associated with exposure to this agent:


Industrial Processes with risk of exposure: