Pharmacological effects:
Classification: Antineoplastic, antimetabolite
Action / Kinetics: An oral prodrug of 5'-deoxy-5-fluorouridine (5'DFUR) that is converted to 5-fluorouracil (5-FU). 5-FU is metabolized to 5-fluoro-2-deoxyuridine monophosphate (FdUMP ) and 5-fluorouridine triphosphate (FUTP) which cause cell injury in two ways. First, FdUMP and the folate cofactor, N5-10-methylenetetrahydrofolate, bind to thymidylate synthase to form a covalently bound ternary complex which inhibits the formation of thymidylate from uracil . Thymidylate is essential for the synthesis of DNA so a deficiency inhibits cell division. Secondly, nuclear transcriptional enzymes can mistakenly incorporate FUTP in place of uridine triphosphate during RNA synthesis; this interferes with RNA processing and protein synthesis. Readily absorbed from the GI tract. Peak blood levels, capecitabine: 1.5 hr; peak blood levels, 5-FU: 2 hr. Food reduces the rate and extent of absorption. t1 / 2, capecitabine and 5-FU: 45 min. Metabolites excreted in the urine.

Indications:
Metastatic breast cancer in those resistant to both paclitaxel and an anthracycline-containing chemotherapy regimen or resistant to paclitaxel and for whom further anthracycline therapy is not indicated (eg, those who have received cumulative doses of 400 mg/m2 of doxorubicin or doxorubicin equivalents).