Doxorubicin and daunorubicin plasmatic, hepatic and renal disposition in the rabbit with or without enterohepatic circulation.

The pharmacokinetics, metabolism and disposition of doxorubicin and daunorubicin were studied for periods up to 100 hr in rabbits with (group II) or without a biliary fistula (groups I and III) and with (group I) or without (groups II and III) ligatured ureters using high-performance liquid chromatography to separate parent drug and metabolites. The plasma decay of doxorubicin and daunorubicin was triexponential. Metabolites appearing in the plasma after doxorubicin and daunorubicin bolus i.v. injection were respectively doxorubicinol and daunorubicinol, the latter being the major compound after daunorubicin injection. The elimination of daunorubicin was faster than that of doxorubicin. No differences in the elimination were observed between the 3 groups. In bile, 21% of the injected dose of doxorubicin were excreted mainly as the parent drug and 60% of the injected dose of daunorubicin were excreted, mainly as daunorubicinol. Enterohepatic circulation did not affect the biliary excretion of both doxorubicin and daunorubicin. Ligature of ureters increased slightly the biliary excretion of doxorubicin. The hepatic clearance of daunorubicin was greater than that of doxorubicin. The total urinary excretion was not different between the II and III groups and amounted to 11.6 and 12.8% of the injected dose of doxorubicin and daunorubicin, respectively. Metabolic ratios of doxorubicinol/doxorubicin and daunorubicinol/daunorubicin were similar in bile and urine.