NCIt definition : A modulator of 5-fluorouracil (5-FU) activity and inhibitor of the enzyme orotate
phosphoribosyl-transferase (OPRT), with chemoprotective activity. Oteracil preferentially
localizes in the gastrointestinal (GI) tract where it inhibits OPRT, thereby decreasing
metabolism of 5-FU into its active metabolite 5-fluorouridine-5'-monophosphate (FUMP).
This decreases activated 5-FU-related gastrointestinal toxicity.;