Comparison of the adsorptive properties of activated charcoal and alaskan montmorillonite for some common poisons

Abstract

Activated charcoal and our own preparation of Alaskan montmorillonite have been compared in vitro with respect to their adsorption isotherms at 37° for six common poisons. When evaluated on the basis of the maximum adsorption capacity and dissociation constant in 0.1 N HCl (“artificial gastric juice”), montmorillonite adsorbs d-amphetamine, tripelennamine, ferrous sulfate, and ethyl alcohol about as well as activated charcoal. With substances which are not ionized at the pH of gastric juice, notably salicylic acid and pentobarbital, a 100-fold difference in dissociation constants and a 3- to 13-fold difference in adsorption capacities occur in favor of charcoal. Both adsorbents are expected to dissociate free salicylate if allowed to pass into the intestinal tract. When the pH rises from 1 to 7.4, the dissociation constant of the salicylate-charcoal complex increases 5-fold and the capacity decreases 3-fold. Over the same pH range, however, the montmorillonite-salicylate complex increases its dissociation constant more than 10-fold and decreases its capacity more than 50-fold. Despite its less acceptable appearance, activated charcoal is judged to be superior to montmorillonite as a gastrointestinal adsorbent for general clinical use in acute poisonings.