How Fluorouracil Injection (5-FU) Works

Fluorouracil is an anti-cancer compound included in a group of drugs called antimetabolites. The drug is used as palliative care for patients with breast cancer, colorectal cancer, gastric (stomach) cancer, and pancreatic cancer, and it is available both as an injection and topical ointment. Being an antimetabolite, fluorouracil works by mimicking the work of normal substances in the cells that affect the cellular metabolism, making the cells unable to divide. The process of cellular division is needed for the cancer to grow, and by attacking it at very specific phases of the cycle, fluoroucacil is expected to slow cancer growth. Since this drug interferes with DNA and RNA synthesis, it is considered a pyrimidine analog.

The National Cancer Institute (NCI) Drug Dictionary defines fluorouracil as “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.”

Fluorouracil Injection (5-FU) for Breast Cancer

Fluorouracil injection, also known as 5-FU, was approved by the U.S. FDA in October 1999. It is produced by the company Gensia Sicor Pharmaceuticals. In the case of breast cancer, the main indication of fluorouracil is to help relieve the symptoms of the disease in advanced stage patients, which means that is is used as palliative care.

“All dosages are based on the patient’s actual weight. However, the estimated lean body mass (dry weight) is used if the patient is obese or if there has been a spurious weight gain due to edema, ascites or other forms of abnormal fluid retention,” according to the informational labeling about fluorouracil’s safety.

“It is recommended that prior to treatment each patient be carefully evaluated in order to estimate as accurately as possible the optimum initial dosage of fluorouracil.”

Treatment with fluorouracil injection can cause adverse events; 30 percent of patients experience diarrhea, nausea, and occasional vomiting, mouth sores, poor appetite, watery eyes, sensitivity to light (photophobia), taste alterations, a metallic taste in the mouth during infusion, discoloration along vein, and low blood counts. More rare side effects include skin reactions, hair-thinning, nail changes, or hand-foot syndrome.

Note: Breast Cancer News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

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