THE INTERACTION OF ALBUMIN AND DRUGS WITH 2 HEMOFILTRATION MEMBRANES

The sorption of phenobarbitone sodium, barbitone sodium and fluconazol e onto haemofiltration membranes made from polysulphone or a co-polyme r of polyamide and polyvinylpyrrolidone was investigated in the presen ce and absence of albumin. The sorption of albumin was also followed i n the presence of phosphate-buffered saline. Drug binding to the membr ane was found to be reversible. Knowledge of the lipophilicity of the drug and hydrophobic/hydrophilic nature of the membrane did not allow successful prediction of the extent of binding of all the drugs; nor d id knowledge of the extent of ionization of the drug and the charge of the membrane. Albumin bound to the polysulphone membrane in a manner that suggested the surface area to which it was binding was around 10 times greater than reported. In the presence of albumin there was a la rger coefficient of variation in the binding of drugs to both membrane s. The presence of albumin significantly decreased the binding of fluc onazole, but not the other drugs, to the polysulphone membrane; howeve r, albumin had no effect on the binding of any of these drugs to the p olyamide membrane. We conclude that the binding of drugs to haemofiltr ation membranes cannot be simply predicted from knowledge of the hydro philic/hydrophobic nature or charge of the drug and membrane, nor from the protein binding of the drug.