1. A method of increasing the systemic exposure of rifaximin (AUCtau) in a subject after oral administration, comprising: selecting a subject having liver failure； the oral administration of rifaximin to a subject having liver failure, where the systemic exposure of rifaximin is increased in a subject with liver failure compared to a subject without liver failure. 2. The method of claim 1, wherein the liver failure in a subject has an index model of the terminal stage of liver disease (MELD) of less than 11 for the subject. The method of claim 1, wherein the liver failure in a subject has an index model of the terminal stage of liver disease (MELD) in the range of 11 to 18 for the subject. The method of claim 1, wherein the liver failure in a subject includes a diagnosis of mild hepatic impairment (Child-Pugh A) for the subject. The method of claim 1, wherein the liver failure in a subject includes a diagnosis of chronic alcoholic liver damage (Child-Pugh B) for the subject. The method of claim 1, wherein the systemic effect of rifaximin in a subject suffering from liver failure includes an effect of at least 5 times that of a subject without liver failure. The method according to claim 1, wherein the systemic effect of rifaximin in a subject suffering from liver failure includes an effect of at least 9.6 times greater than that in a subject without liver failure. The method according to claim 1, where the systemic effect of rifaximin in a subject suffering from liver failure includes an effect of at least 13.1 times greater than that in a subject without liver1. Способ увеличения системного воздействия рифаксимина (AUCtau) у субъекта после перорального введения, включающий:отбор субъекта, имеющего печеночную недостаточность； ипероральное введение рифаксимина субъекту, имеющему печеночную недостаточность, где системное воздействие рифаксимина увеличено у субъекта с печеночной недостаточностью по сравнению с субъектом без печеночной недостаточности.2. Способ по п.1,
