Factors modifying the toxicity of organophosphorus compounds including dichlorvos

The effect of repetitive doses of organophosphorus agents in experimental animals has been studied. The cumulative LD50 dose depended upon the time interval between injections of toxic agent. From these data it was possible to obtain the rate of detoxification of these agents. In the case of soman and sarin TOCP pretreatment, an inhibitor of plasma aliesterase, modified both the acute LD50 and the rate of detoxification. The results therefore suggest that recovery of plasma aliesterase contributes to a large extent in detoxification of chronically administered soman and sarin. In contrast, tolerance to chronically administered dichlorvos can not be correlated to recovery of plasma aliesterase, but correlates well with a rapid spontaneous reactivation of acetylcholinesterase.