indication

For palliative management of gastrointestinal adenocarcinoma metastatic to the liver, when given by continuous regional intra-arterial infusion in carefully selected patients who are considered incurable by surgery or other means. Also for the palliative management of liver cancer (usually administered by hepatic intra-arterial infusion).

pharmacology

Floxuridine is a pyrimidine analog that acts as an inhibitor of the S-phase of cell division. This selectively kills rapidly dividing cells. Floxuridine is an anti-metabolite. Anti-metabolites masquerade as pyramidine-like molecules which prevents normal pyrimidines from being incorporated into DNA during the S phase of the cell cycle. Flurouracil (the end-product of catabolism of floxuridine) blocks an enzyme which converts cytosine nucleosides into the deoxy derivative. In addition, DNA synthesis is further inhibited because fluoruracil blocks the incorporation of the thymdine nucleotide into the DNA strand.

mechanism of action

Floxuridine is rapidly catabolized to 5-fluorouracil, which is the active form of the drug. The primary effect is interference with DNA synthesis and to a lesser extent, inhibition of RNA formation through the drug's incorporation into RNA, thus leading to the production of fraudulent RNA. Fluorouracil also inhibits uracil riboside phophorylase, which prevents the utilization of preformed uracil in RNA synthesis. As well, the monophosphate of floxuridine, 5-fluoro-2'-deoxyuridine-5'-phosphate (FUDR-MP) inhibits the enzyme thymidylate synthetase. This leads to the inhibition of methylation of deoxyuridylic acid to thymidylic acid, thus interfering with DNA synthesis.

toxicity

Oral, rat LD₅₀: 215 mg/kg. Signs of overdose include nausea, vomiting, diarrhea, gastrointestinal ulceration and bleeding, and bone marrow depression (including thrombocytopenia, leukopenia and agranulocytosis).

biotransformation

Hepatic.

route of elimination

The drug is excreted intact and as urea, fluorouracil, a-fluoro-bureidopropionic acid, dihydrofluorouracil, a-fluoro-b-guanidopropionic acid and a-fluoro-b-alanine in the urine; it is also expired as respiratory carbon dioxide.

drug interactions

Tamoxifen: Floxuridine may reduce clearance rate of Tamoxifen. Monitor for changes in therapeutic/adverse effects of Tamoxifen if Floxiridine is initiated, discontinued or dose changed.

Tolbutamide: Floxuridine, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of Tolbutamide, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in Tolbutamide therapeutic and adverse effects if Floxuridine is initiated, discontinued or dose changed.

Torasemide: Floxuridine, a strong CYP2C9 inhibitor, may increase the serum concentration of Torasemide, a CYP2C9 substrate, by decreasing Torasemide metabolism and clearance. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of Torasemide if Floxuridine is initiated, discontinued or dose changed.

Trastuzumab: Trastuzumab may increase the risk of neutropenia and anemia. Monitor closely for signs and symptoms of adverse events.

Trimethoprim: The strong CYP2C9 inhibitor, Floxuridine, may decrease the metabolism and clearance of Trimethoprim, a CYP2C9 substrate. Consider alternate therapy or monitor for changes in therapeutic and adverse effects of Trimethoprim if Floxuridine is initiated, discontinued or dose changed.

Voriconazole: Floxuridine, a strong CYP2C9 inhibitor, may increase the serum concentration of voriconazole by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of voriconazole if floxuridine is initiated, discontinued or dose changed.

Warfarin: Floxuridine, a strong CYP2C9 inhibitor, may decrease the metabolism of warfarin. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of warfarin if floxuridine is initiated, discontinued or dose changed.

Zafirlukast: Floxuridine, a strong CYP2C9 inhibitor, may decrease the metabolism and clearance of zafirlukast. Consider alternate therapy or monitor for changes in zafirlukast therapeutic and adverse effects if floxuridine is initiated, discontinued or dose changed.