Effect of Activated Charcoal and Atropine on Absorption and/or Exsorption of Organophosphorus Compounds in Rats

Abstract

Effects of activated charcoal and atropine for the removal of organophosphorus compounds, which remain in the gastrointestinal tract or have already been absorbed into the systemic circulation, were investigated in rats. Activated charcoal extensively adsorbed the organophosphates fenitrothion, tolclofos methyl, piperophos and salithion, and its immediate administration after oral ingestion of fenitrothion remarkably reduced serum fenitrothion levels, but had no effect on the serum levels of the compound which had been absorbed from the gastrointestinal tract. Thus, all of the organophosphorus compounds were poorly exsorbed (0.002-0.39% of the dose in 120 min) from the blood into the intestinal lumen probably due to their extensive protein binding and large distribution volumes. Atropine inhibited absorption of fenitrothion in the perfusion in-situ and also delayed the absorption of the compound in-vivo, but had no significant effect on exsorption of fenitrothion. The serum fenitrothion levels on treatment with both atropine and charcoal significantly decreased compared with those of the control. We conclude that, oral activated charcoal will not be able to enhance the elimination of organophosphorus compounds which have already been absorbed into the systemic circulation, but constitute a useful method for the removal of the compounds remaining in the gastrointestinal tract because of its excellent adsorptive capacity.