Also known as 5-FU, 5-Fluoracil, 5-Fluorouracil, 5-Fluracil, AccuSite, Adrucil, Carac, FU, Fluoro Uracil, Fluorouracilo, Fluorouracilum, Fluouracil, Flurablastin, Fluracedyl, Fluracil, Fluril, Fluroblastin, Ribofluor, Ro 2-9757

An antimetabolite fluoropyrimidine analog of the nucleoside pyrimidine with antineoplastic activity. Fluorouracil and its metabolites possess a number of different mechanisms of action. In vivo, fluoruracil is converted to the active metabolite 5-fluoroxyuridine monophosphate (F-UMP); replacing uracil, F-UMP incorporates into RNA and inhibits RNA processing, thereby inhibiting cell growth. Another active metabolite, 5-5-fluoro-2′-deoxyuridine-5′-O-monophosphate (F-dUMP), inhibits thymidylate synthase, resulting in the depletion of thymidine triphosphate (TTP), one of the four nucleotide triphosphates used in the in vivo synthesis of DNA. Other fluorouracil metabolites incorporate into both RNA and DNA; incorporation into RNA results in major effects on both RNA processing and functions.

Originator: NCI Thesaurus | Source: The website of the National Cancer Institute (http://www.cancer.gov)

Can I take Fluorouracil while breastfeeding?

Most sources consider breastfeeding to be contraindicated during maternal antineoplastic drug therapy. It might be possible to breastfeed safely during intermittent therapy with an appropriate period of breastfeeding abstinence, but the duration of abstinence is not clear. Limited information indicates that a maternal continuous intravenous fluorouracil infusion at a dose of 200 mg/square meter daily produces undetectable levels in milk. If fluorouracil use is undertaken, monitoring of the infant’s complete blood count and differential is advisable. Topical fluorouracil applied away from the breast should pose negligible risk for the breastfed infant; however, it is important to ensure that the infant’s skin does not come into direct contact with the areas of skin that have been treated.

Drug levels

Maternal Levels. A mother who was 9 months postpartum was diagnosed with rectal cancer and began treatment with pelvic radiotherapy and a continuous intravenous infusion of fluorouracil 200 mg/square meter daily. Her plasma fluorouracil concentration was constant at about 110 micromoles/L (14.3 mg/L) from weeks 2 to 5 of therapy. She discontinued nursing her infant and pumped her breasts twice daily and collected 36 breastmilk samples before, during and for 10 days following fluorouracil therapy (exact times not specified). Fluorouracil was undetectable (<0.5 micromol/L [<65 mcg/L]) in all of the milk samples.[1] Infant Levels. Relevant published information was not found as of the revision date.

Effects in breastfed infants

Maternal Levels. A mother who was 9 months postpartum was diagnosed with rectal cancer and began treatment with pelvic radiotherapy and a continuous intravenous infusion of fluorouracil 200 mg/square meter daily. Her plasma fluorouracil concentration was constant at about 110 micromoles/L (14.3 mg/L) from weeks 2 to 5 of therapy. She discontinued nursing her infant and pumped her breasts twice daily and collected 36 breastmilk samples before, during and for 10 days following fluorouracil therapy (exact times not specified). Fluorouracil was undetectable (<0.5 micromol/L [<65 mcg/L]) in all of the milk samples.[1] Infant Levels. Relevant published information was not found as of the revision date.

Possible effects on lactation

Relevant published information was not found as of the revision date.

References

Peccatori FA, Giovannetti E, Pistilli B et al. “The only thing I know is that I know nothing”: 5-fluorouracil in human milk. Ann Oncol. 2012;23:543-4. PMID: 22275286

Last Revision Date

20160401

Disclaimer:Information presented in this database is not meant as a substitute for professional judgment. You should consult your healthcare provider for breastfeeding advice related to your particular situation. The U.S. government does not warrant or assume any liability or responsibility for the accuracy or completeness of the information on this Site.

Source: LactMed – National Library of Medicine (NLM)

3D Model of the Fluorouracil molecule

MolView – data visualization platform