Response of rabbit whole-blood cholinesterase in vivo after continuous intravenous infusion and percutaneous application of dimethyl organophosphate inhibitors

The in vivo reactions of three dimethyl organophosphates with rabbit whole-blood cholinesterase were studied during continuous intravenous infusion or percutaneous application of these compounds. 3-(Dimethoxyphosphinyloxy)-N,N-dimethylcrotonamide (Bidrin) was poorly absorbed when applied as an undiluted liquid; 1-carbomethoxy-1-propen-2-yl dimethyl phosphate (Phosdrin) and DDVP, 2,2-dichlorovinyl dimethyl phosphate (Vapona) were absorbed more readily. The absorption of Bidrin, Phosdrin, and Vapona was enhanced when the compounds were applied with dimethylsulfoxide. Whole-blood cholinesterase was progressively inhibited during intravenous infusion of the compounds, followed by rapid but incomplete reversal of enzyme inhibition during an immediate postinfusion period. Differences in the enzyme inhibition and recovery curves are discussed in relation to possible mechanisms of in vivo inhibition. Theoretical equations, derived from the experimental data and programmed into an analog computer, successfully described the inhibition process.