1. The ability of activated charcoal, treated in differing ways with poly(hydroxyethylmethacrylate), to adsorb paracetamol was studied.
2. Activated charcoal was coated with 2, 4 or 10% by weight of poly(hydroxyethylmethacrylate). Neither the percentage by weight (2, 4 or 10%) coating of activated charcoal by the polymer nor the procedure used to apply the coat affected the total adsorption of paracetamol at equilibrium, but these factors did influence the speed of adsorption.
3. The impregnated charcoals, and those with the lowest percentage by weight coating (2%), removed paracetamol from a stirred solution most rapidly. These charcoals also removed the drug most efficiently during column perfusion.
4. Biocompatibility studied in vivo in the dog revealed a smaller fall in blood platelets with haemoperfusion through 4% encapsulated charcoal than with 4% impregnated charcoal.
5. Dye-adsorption studies indicated that impregnation produced less complete coating of the charcoal, and that the lower percentage by weight coatings were the least complete.
6. The most acceptable compromise for clinical use appeared to be the 4% encapsulated charcoal, as the removal of paracetamol was reasonably rapid and the fall in blood platelet levels was acceptable.