Complete urinary excretion profile of 5-fluorouracil during a six-day chemotherapeutic schedule, as resolved by 19F nuclear magnetic resonance.

We determined the urinary excretion of 5-fluorouracil (5FU) and its metabolites during six days of chemotherapy, using the non-invasive approach of 19F nuclear magnetic resonance. With this method, which requires no labeled drug, one can study the biological sample directly and simultaneously identify and quantify all the fluorinated metabolites. The daily urinary excretion of 5FU and its metabolites was high (94.8% of 5FU administered) and nearly constant all during the treatment. By far the major excreted catabolite was alpha-fluoro-beta-alanine, which made up 78.9% of the total. Unchanged 5FU (10.8% of dose injected) was found only during the first 2 h after injection. We observed neither accumulation of 5FU nor modifications in its metabolism during the treatment.