[Determination of protein binding of drugs using equilibrium dialysis. Influence of volume displacement caused by osmotic pressure].

By the determination of the free concentration of a drug using the equilibrium dialysis method, a volume shift could be observed, inducing a dilution of the protein medium. The value of this volume shift varies with the plasmatic sample and could produce a misdetermination of the free fraction which could be important, essentially for the drugs strongly bound to proteins.