Evidence is presented to show that tannic acid is responsible for the reduced effectiveness of "universal antidote" as compared with activated charcoal alone. Adsorption isotherm data indicate that tannic acid binds strongly to charcoal and hence uses up part of the adsorption capacity that would otherwise be available for binding of a drug or poison. Data on sodium salicylate adsorption from simulated gastric fluid, both with and without the presence of tannic acid, are presented that illustrate clearly that tannic acid interferes significantly with the adsorption of salicylate. Magnesium oxide, another component of "universal antidote," was found to offer no interference to salicylate adsorption, presumably because it does not adsorb to charcoal to any significant extent.
Clearance versus time tests were carried out on three charcoal-based hemoperfusion devices (Sandev, Becton-Dickinson and Gambro) using solutions of 1 gm/L sodium salicylate in a pH 7.4 buffer and in bovine blood at flow rates of 200 rnl/min. Similar tests were performed on a Cordis Dow 2.5 m2 hollowfiber dialyzer at a tube side flow rate (QB) of 200 ml/min. Buffer was pumped through the dialysate side at a flow rate (QD) of 400 ml/min. Two dialyzers were run in series at QB = 200 ml/min and QD = 500 or 1000 ml/min. Mass transfer resistances were computed from the test results. These values are useful in that they constitute an index of the intrinsic initial kinetics of solute transfer in each device. However, the clearance versus time curves indicate that these initial kinetics decrease at different rates for each hemoperfusion unit as sorption capacity begins to be depleted. In contrast, the initial clearances for the dialyzers remain at their initial values. These data reveal much about the relative mass transfer characteristics of these devices. mass transfer, hemoperfusion, dialyzers, clearances, kinetics Nomenclature A C fluid phase concentration K overall mass transfer coefficient Q volumetric flow rate RT total mass transfer resistance S W total solute transfer rate z axial length B blood or buffer D dialysate total external area for mass transfer external surface area per unit length of column Subscripts
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