Toxicokinetic and toxicodynamic aspects of organophosphorus (OP) insecticide poisoning

As the majority of OP insecticides are lipophilic and not ionised they are absorbed rapidly following ir;halation or ingestion; dermal absorption is s lower but severe poisoning may still ensue if exposure is prolonged. Follow ing absorption, OP compounds accumulate in fat, liver, kidneys and salivary glands. Phosphates (P=O) are biologically active as AChE inhibitors, where as phosphorothioates (P=S) need bioactivation to their phosphate anologues (oxons) to become biologically active. Oxons inhibit AChE by phosphorylatio n of the serine hydroxyl group in the substrate-binding domain of the enzym e. The rate of spontaneous reactivation of alkyl phosphorylated AChE depend s on the chemical structure of the OP compound. Spontaneous reactivation of dimethyl phosphorylated AChE proceeds quite rapidly. However, unless oxime s are employed, there is no such expectation of rapid recovery for patients intoxicated with diethyl phosphoryl insecticides. (C) 1998 Elsevier Scienc e Ireland Ltd. All rights reserved.