The toxicity of organophosphorus compounds to mammals.

The acute toxicity of most of the commonly used organophosphorus insecticides is essentially the same. A few compounds with low toxicity, such as malathion, have been developed but further efforts in that direction are needed. Most of the organophosphorus insecticides exert a generalized cholinergic action by inhibiting central and peripheral cholinesterases. The phosphoramides are an exception in that they do not gain access to the cholinesterase of the central nervous system in vivo and consequently atropine is a more effective antidote for them than for organophosphorus compounds. Young animals are more susceptible to the organophosphorus compounds than are adults. Enzyme-inducing agents decrease the toxicity of the phosphorothioates and phosphorodithioates. All organophosphorus insecticides can inhibit esterases that catalyse the detoxification of some insecticides of this class and ester-type drugs.