Urinary metabolites of busulfan in the rat.

After ip administration of 15 mg/kg [1,4-14C]busulfan to rat, the urinary excretion was 70% of the total radioactivity after 72 hr. Three major metabolites were isolated and quantified by HPLC. Of the total radioactivity in the urine, unchanged busulfan was excreted as a minor amount (6%) and the following metabolites were identified as: 3-hydroxysulfolane (39%), tetrahydrothiophene 1-oxide (20%), and sulfolane (13%) using GC/MS and NMR spectroscopy. The cytotoxicity of busulfan and its major metabolites was examined using a V79 Chinese hamster cell line.