In Vitro Adsorption of Phenobarbital, Chlorpheniramine Maleate, and Theophylline by Four Commercially Available Activated Charcoal Suspensions

Four commercially available antidotal activated charcoal suspensions (Actidose Aqua, InstaChar, LiquiChar, and CharcoAid 2000) were evaluated with respect to their abilities to adsorb three test drugs in vitro from simulated gastric fluid. Different volumes of each suspension were added to glass vials containing 20 mL of stock solutions of each drug. The vials were shaken for a time more than sufficient to ensure adsorption equilibrium, then the charcoal was removed from the samples by filtration. The filtrates were analyzed by ultraviolet spectroscopy to determine the residual drug concentrations. The product containing a 2000 m2/g charcoal (CharcoAid 2000) adsorbed more drug per unit volume of suspension than did the other three products, which contained 900 m2/g charcoal and which were all similar in performance.