1 Organophosphorus Pesticides: Pharmacology

Abstract

Pesticides and agricultural chemicals are used to maintain an adequate food supply for the ever-increasing world population. A large number belong to the organophosphorus family and are biologically active against economically important parasitic pests. The organophosphorus compounds, currently in use, have a margin of safety between their effective use concentrations and their minimum toxic concentrations to mammals. However, it is always possible that mammals may become overexposed to these compounds or to toxic residues of these compounds following the application of excessive amounts to crops, either by hazard, by negligent handling or by intentional self-administration. A full understanding of the mechanism of their biological effects is therefore necessary so that these chemicals may be handled safely and effective remedies may be made available to counteract the effects of overexposure. The principal biological effect of organophosphorus chemicals in the mammalian system is the inhibition of cholinesterases. The pharmacology of the organophosphorus cholinesterase inhibitors has many facets. Much has been discovered concerning their mode of action and the therapeutic measures to be adopted in the event of intoxication by these compounds. The chapter summarizes recent developments in the understanding of the mode of action of the organophosphorus compounds in mammals.