Radioactive species in rat urines and tissues after [14C] AD 32 administration

[14-14C]N-Trifluoroacetyldoxorubicin-14-valerate [( 14C]AD 32) was synthesized and administered IV to male rats at 9.09 mg/kg. Urinary radioactivity excreted in the 0-24 h interval was only 2.3% of the dose, N-trifluoroacetyldoxorubicin (AD 41), 13-dihydro-N-trifluoroacetyldoxorubicin (AD 92), and doxorubicin being the major urinary metabolites identified. Doxorubicin and AD 32 were the main radioactive species extracted from tissues at 24 h after treatment. The amount of doxorubicin present in the analysed tissue samples is in agreement with the relatively low toxicity of AD 32 compared with doxorubicin.