[Methods of determination and theoretical principles of the serum protein binding of drugs (author's transl)].

A survey is given of the methods applied in the determination of protein binding (electrophoresis, ultrafiltration, gel-filtration, ultracentrifugation, dialysis and microbiological plate test). Basing on our own investigations as well as on papers by other authors the possibilities of errors and limitations of the methods are discussed. The protein binding is reversible and can be explained by the law of mass action. By the representation of the test results according to Scatchard plot it is possible to ascertain the number of the binding groups of the albumin molecule and the equilibrium constant of the reaction. Based on these results the affinity (free reaction, energy) of the protein binding can be calculated. The protein binding can be described especially in therapeutical concentration rather well by the Freundlich isothermal curve. The binding powers which cause the protein binding are discussed. The examination of various substance groups, such as sulphonamides, antibiotics and steroid hormones has shown that the hydrophobic binding plays the main role in the binding of drugs to albumin. As an example of an ionogenic binding the binding or aminoglycosides to alubmin is discussed.