Effect of sodium taurodeoxycholate (TDC) on the pharmacokinetics of methylene blue (MB) was investigated in the rats of experimental hepatic failure induced by $CCI_4$. Intravenous infusion of TDC increased the distribution volume of central compartment ($Vd_1$) and the total body clearance ($CL_t$) of MB. Increased lipophilicity through ion-pair formation with TDC seemed to be the probable cause of increased $Vd_1$ and $CL_t$.