Medically Reviewed on 10/10/2022

Generic Name: fluorouracil

Brand Name: Adrucil (discontinued brand)

Drug Class: Antineoplastics, Antimetabolite

What is fluorouracil, and what is it used for?

Fluorouracil (5-FU) is a chemotherapy medication used in the treatment of some cancers including gastric, pancreatic, colorectal, and breast cancers in adults. Fluorouracil is used as a systemic drug administered as intravenous injection in these cancers.

In addition, topical formulations of fluorouracil are used to treat certain types of skin cancers. Fluorouracil is an antimetabolite antineoplastic drug that interferes with cellular metabolic process and synthesis of DNA and RNA, which affects rapidly growing cancer cells leading to their death.

Fluorouracil is a pyrimidine analog that has a structure similar to pyrimidine, one of the compounds that are the building blocks of DNA and RNA. Inside the body, fluorouracil gets converted into its active metabolites which get incorporated into the DNA and RNA in place of the pyrimidines required for the synthesis of DNA and RNA. The fluorouracil metabolites inhibit cell growth and inhibit thymidylate synthase, an enzyme that is essential for DNA replication and repair, leading to extensive DNA damage and cellular death.

4 types of cancer 

The uses of fluorouracil include:




  • Fluorouracil injection should be administered only under the supervision of an experienced cancer chemotherapy physician because of the possibility of severe toxic reactions.
  • Patient should be hospitalized for the initiation of fluorouracil therapy because of the risk for severe toxic reactions.
  • Patients with low or absent dipyrimidine dehydrogenase (DPD) activity due to gene mutations are at a higher risk for serious or fatal adverse reactions. DPD is an enzyme that breaks down pyrimidine derivates thymine and uracil.
    • Monitor patients for evidence of acute early-onset or unusually severe toxicity which may indicate reduced or absent DPD activity. Withhold or permanently discontinue fluorouracil based on clinical assessment.
    • No fluorouracil dose has been proven safe for patients with absent DPD activity and there is insufficient data to recommend a dose for partial DPD activity.
  • Fluorouracil can cause toxicity to various body systems. Patients should be monitored for symptoms and fluorouracil should be withheld if toxicities occur and appropriate therapies instituted. The risks of resumption of fluorouracil after the toxicities have resolved have not been established. Fluorouracil associated toxicities include:
    • Cardiotoxicity: Risk factors include administration by continuous infusion and presence of coronary artery disease.
    • Hyperammonemic encephalopathy: Elevated ammonia in blood and associated brain damage, with no identifiable cause.
    • Neurologic toxicity: Neurological events such as acute cerebellar syndrome that affect balance, coordination and gait, confusion, disorientation, and visual disturbances.
  • Fluorouracil can cause severe diarrhea. Administer fluids, electrolyte replacement, or antidiarrheal treatments as necessary, and withhold fluorouracil for Grade 3 or 4 diarrhea until resolved or decreased in intensity to Grade 1, then resume fluorouracil at a reduced dose.
  • Fluorouracil can cause inflammation of the gastrointestinal mucous membrane (stomatitis, mucositis, and esophagopharyngitis) resulting in the sloughing of mucous membrane or ulcerations. Withhold fluorouracil for Grade 3 or 4 mucositis and resume fluorouracil at a reduced dose once mucositis has resolved or reduced in severity to Grade 1.
  • Fluorouracil can cause fetal harm. Advise women of reproductive potential and men with female partners to use effective contraception during fluorouracil treatment and for up to 3 months following cessation of therapy.
  • Fluorouracil can cause hand-foot syndrome (palmar-plantar erythrodysesthesia), symptoms of which include pain, tingling, swelling, tenderness, peeling, and redness in palms and feet soles. Administer treatment for symptom relief, withhold fluorouracil administration for Grade 2 or 3, and resume fluorouracil at a reduced dose when the condition is completely resolved or decreased in severity to Grade 1.
  • Fluorouracil can suppress bone marrow function resulting in decreased blood cell counts. Obtain complete blood counts prior to each treatment cycle and as needed. Withhold fluorouracil until Grade 4 myelosuppression resolves; resume fluorouracil at a reduced dose when myelosuppression has resolved or improved to Grade 1 in severity.
  • Concomitant use with anticoagulant medications such as warfarin can increase blood clotting time. Monitor the patient and adjust anticoagulant dosage appropriately.


Skin Cancer Symptoms, Types, Images See Slideshow

What are the side effects of fluorouracil?

Common side effects of fluorouracil include:

Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

What are the dosages of fluorouracil?

Injectable Solution

  • 50 mg/mL


Colon and Rectal Cancer

  • 400 mg/m² intravenous push (IVP) injection on Day 1, followed by 2400-3000 mg/m² IV as a continuous infusion over 46 hours every 2 weeks in combination with leucovorin with or without oxaliplatin/irinotecan

Breast Cancer

  • 500 or 600 mg/m² IV on Days 1 and 8 every 28 days for 6 cycles as a component of a cyclophosphamide-based multidrug regimen

Gastric Cancer

  • 200-1000 mg/m²/day as a continuous infusion over 24 hours (as part of a platinum-containing regimen)
  • Duration and frequency of each cycle varies based on dose and regimen

Pancreatic Cancer

  • 400 mg/m² IVP on Day 1, followed by 2400 mg/m² IV as a continuous infusion over 46 hours every 2 weeks
  • Combination with leucovorin or as a component of a multidrug chemotherapy regimen that includes leucovorin, is 400 mg/m² IVP on Day 1, followed by 2400 mg/m² IV as a continuous infusion over 46 hours every 2 weeks

Other Indications and Uses

  • Off-label use for cervical, bladder, hepatic, prostate, endometrial, and head and neck carcinoma


  • Safety and efficacy not established


  • Fluorouracil overdose can cause life-threatening bone marrow suppression (myelosuppression) including low platelet count (thrombocytopenia), gastrointestinal complications, mucous membrane inflammation (mucositis), weakness (asthenia) irregular heart rhythms (cardiac arrhythmia), swelling (edema) of hands and feet, and neurotoxicity.
  • Fluorouracil overdose is treated with oral administration of uridine triacetate within 96 hours after overdose. The safety and efficacy of uridine triacetate administration after 96 hours following fluorouracil infusion is unknown.

What drugs interact with fluorouracil?

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

  • Fluorouracil has no known severe interactions with other drugs.
  • Serious interactions of Fluorouracil include:
    • adenovirus types 4 and 7 live, oral
    • axicabtagene ciloleucel
    • brexucabtagene autoleucel
    • ciltacabtagene autoleucel
    • deferiprone
    • erdafitinib
    • germanium
    • idecabtagene vicleucel
    • influenza virus vaccine quadrivalent, adjuvanted
    • influenza virus vaccine trivalent, adjuvanted
    • lisocabtagene maraleucel
    • palifermin
    • ropeginterferon alfa 2b
    • siponimod
    • tinidazole
    • tisagenlecleucel
    • tofacitinib
  • Fluorouracil has moderate interactions with at least 40 different drugs.
  • Mild interactions of fluorouracil include:

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

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Pregnancy and breastfeeding

  • There are no adequate and well-controlled studies of fluorouracil use in pregnant women. Animal studies indicate that fluorouracil may impair both male and female fertility.
  • Fluorouracil can cause fetal malformations or loss of pregnancy if administered during pregnancy. Women of pregnancy potential should use effective contraception during fluorouracil treatment and for up to 3 months following cessation of therapy.
  • Fluorouracil can damage spermatozoa. Men with female partners should use effective contraception during fluorouracil treatment and for up to 3 months following cessation of therapy.
  • It is not known if fluorouracil and its metabolites are present in breast milk, however, many drugs are present in breast milk. Decision should be made to discontinue nursing or the drug, taking into account the importance of the drug to the mother, because of the potential for serious adverse effects in the breastfed infant from fluorouracil.

What else should I know about fluorouracil?

  • While you are on fluorouracil therapy, you will need regular blood tests, keep up with your appointments.
  • Notify your physician if you have a known dipyrimidine dehydrogenase (DPD) deficiency before the initiation of fluorouracil therapy.
  • Contact your physician immediately if you develop:
    • Heart-related symptoms such as chest pain, dizziness or shortness of breath
    • Confusion, disorientation, difficulty with balance and coordination, or visual disturbances
    • Severe diarrhea or mouth sores
    • Tingling or burning, redness, flaking, swelling, blisters, or sores on your palms or feet soles


Fluorouracil (5-FU) injection is a chemotherapy medication used in the treatment of some cancers including gastric, pancreatic, colorectal, and breast cancers in adults. Common side effects of fluorouracil include nausea, vomiting, diarrhea, loss of appetite (anorexia), oral inflammation (stomatitis), inflammation of the throat and esophagus (esophagopharyngitis), reduced blood flow to the intestinal region (mesenteric ischemia), gastrointestinal (GI) tissue sloughing, GI ulcer, GI hemorrhage, plaque buildup in coronary arteries (coronary arteriosclerosis), chest pain associated with coronary artery disease (angina pectoris), irregular heart rhythm (cardiac arrhythmia), and others.

Treatment & Diagnosis

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Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Medically Reviewed on 10/10/2022