Physiological disposition of a series of rifamycins in rat: a comparative study.

The disposition of four C3-substituted piperazinyl rifamycins was studied in the rat following the intravenous administration of 5 mg/kg of the 14C-labelled antibiotics. Considerable quantitative differences in the pharmacokinetics of these antibiotics were shown in blood levels, tissue distributions and body clearances. Feces were largely the major route of elimination for the parent drug and metabolites. The results suggest that the liver compartimentalization, regulating the biliary excretion, is to be the kinetic parameter affecting the pharmacokinetic behaviour of this class of antibiotics.