Doxorubicin pharmacokinetics in the rabbit.

The levels of doxorubicin, doxorubicinol and DOX aglycone achieved in plasma, urine and feces after i.v. administration of doxorubicin at 7.9 mg/kg into five New Zealand White rabbits were determined by high-performance liquid chromatography and fluorometry. The parent drug was the major compound found in the plasma. Doxorubicinol and DOX aglycone only appeared in trace amounts in the plasma. The plasma disappearance curves were triphasic with mean half-lives of 2 min, 18 min and 15 h for the alpha-, beta- and gamma-phases, respectively. Plasma protein binding was studied by ultracentrifugation and electrophoresis. Doxorubicin was mainly bound to albumin to an extent of 73.9%. The mean percentage of the administered dose excreted in the urine was 8.0%. Doxorubicinol and doxorubicin were the major compounds present in the urine with small amounts of DOX aglycone. Neither the parent drug nor any fluorescent metabolites were identified in the feces. The rabbit seems to be a good experimental model for the pharmacokinetics study of anthracyclines since the plasma and urine pharmacokinetics parameters and the extent of metabolism are similar in both humans and rabbits.