Studies on the protein binding of antituberculous drugs were carried out by using equilibrium dialysis method to clarify several clinical problems on the interaction between drugs and protein. The results were as follows: 1) The factors related to the protein binding rates of sera to PAS were the concentration of drugs and protein in sera, the ratio of the volume in external and internal compartments, etc. As nearly the same binding rates of serum protein to PAS were obtained both in vivo and

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... vitro under the same PAS concentration, the data in this report were obtained mainly by in vitro method. 2) The binding rates of sera to antituberculous drugs were generally low values, while RFP and PAS showed relatively higher rates than other drugs. 3) Marked individual variations were observed in the binding rates of sera to PAS and. RFP,