Cholinesterase inhibition organophosphate nerve agents

Although bicyclophosphates do not inhibit acetylcholinesterase, they exhibit a synergistic toxic effect with materials that do. Individuals who have had previous exposure to cholinesterase inhibitors such as nerve agents and commercial organophosphate or carbamate pesticides may be at a greater risk from exposure to bicyclophosphates. 

Nerve agents are hydrolyzed by the enzyme organophosphate (OP) hydrolase. The hydrolysis of GB, soman (GD), tabun (GA), and diisopropyl flu-orophosphate occurs at approximately the same rate. The isomers of the asymmetric OPs may differ in overall toxicity, rate of aging, rate of cholinesterase inhibition, and rate of detoxification. The rates of detoxification differ for different animal species and routes of administration. The onset of effects from nerve agents depends on the route, duration, and amount of exposure. The effects can occur within seconds to several minutes after exposure. There is no... 

Although the organophosphate insecticides are similar to nerve agents in inhibiting cholinesterase, they differ in other characteristics. For example, the cholinergic crisis caused by acute, severe intoxication with the insecticides is generally much longer... 

Potency of Nerve Agents as Cholinesterase Inhibitors. The potency of the anticholinesterase activity of nerve agents and other organophosphates is measured by either the bimolecular rate constant (kj) for the reaction of the phosphate compound with the enzyme or by the molar concentration causing 50% inhibition of the enzyme (I50) in vitro. The relationship between I50 and kj as a function of time (r) is expressed by the following equation (Eto 1974) ... 

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