Metabolic studies of 5-fluorouracil—II. Influences of the route of administration on the dynamics of distribution in man

Portal and peripheral plasma and bile levels of 5-fluorouracil were determined after oral and intravenous administration of the 2- 14C labelled isotope in man. Initial peak levels of radioactivity resulting from intravenous administration were followed by a rapid disappearance of the isotope. Ingested drug appeared in the portal plasma in less than 5 minutes and resulted in sustained higher concentrations in the plasma and bile 30 to 60 minutes later. Significant 5-fluorouracil is excreted into the gut via the biliary tree. Sustained portal concentrations of active drug suggest that continued absorption from the small intestine occurs.