HUMAN URINARY METABOLITES OF 1-(TETRAHYDRO-2-FURANYL)-5-FLUOROURACIL(FTORAFUR)

Two hydroxylated metabolites were isolated from the urine of a patient who received the antineoplastic drug ftorafur (5 g/m2). These metabolites were identified by mass spectrometry and NMR spectroscopy as trans-3''- and cis-4''-hydroxyftorafur. The compounds were not converted to 5-fluorouracil when incubated in plasma, base (pH 9) or H2O. Because of their stability, it is unlikely that these metabolites are in vivo precursors of 5-fluorouracil. Less stable, unisolatable, hydroxylated ftorafur derivatives may be intermediates in the conversion of ftorafur to 5-fluorouracil.