Distribution of daunorubicin intravenously injected or intravenously infused as free drug and as a complex with DNA in rabbits.

The tissue distribution of daunorubicin (DNR) was investigated in rabbits after 5 mg/kg DNR i.v. bolus injection or 4 h infusion of 5 mg/kg either as free drug or as a complex with DNA. After i.v. bolus, the highest DNR concentration was observed in lungs and kidneys, a lower concentration in heart and spleen and the least in the liver. The DNR biotransformation to daunorubicinol (DNR-ol) and aglycones was most active in kidneys and liver, while heart, lungs and spleen metabolized DNR to a lower extent. The DNR tissue elimination half-life varied from 4.5 to 8.7 h, whereas concentrations of DNR-ol remained elevated for a longer period of time. After 4 h infusion, the only difference when compared with i.v. bolus consisted of a 3-fold lower initial DNR concentration in heart and lungs. No striking difference could be observed after free versus complexed drug infusion except for a somewhat lower DNR concentration in heart and lungs for the complexed drug.