Oteracil

**Semantic type:** Pharmacologic Substance

**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.

**Synonyms:** - OTERACIL - Oxonic Acid