Identification and quantitation of 5-fluorouridine in rat urine after administration of 5-fluorouracil or 5-fluoro-2'-deoxyuridine.

The ribonucleoside 5-fluorouridine was identified in 24-hr urine samples from rats after ip administration of 5-fluorouracil (200 mg/kg) or 5-fluoro-2'-deoxyuridine (380 mg/kg) by means of thin-layer chromatography, high-pressure liquid chromatography, capillary gas-liquid chromatography and gas-liquid chromatography-mass spectrometry techniques, and by comparison with the synthetic compound. By use of a specific extraction procedure, 5-fluorouridine was then quantitatively determined by capillary gas-liquid chromatography with a nitrogen-selective detector. These measurements indicate that not more than 0.2% of the administered dose was excreted as 5-fluorouridine; lower urinary metabolite levels were found after treatment with 5-fluorouracil than after 5-fluoro-2'-deoxyuridine administration. Following an ip dose of either drug, variable amounts of 2'-deoxyuridine and thymidine were detected in the urine samples.