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Drug

Fluorouracil

Pronounced

"flewr-oh-YOUR-uh-sill"

Side Effects

Nausea, vomiting, loss of appetite, dry/itchy skin, or skin darkening may occur. Nausea and vomiting can be severe. In some cases, drug therapy may be necessary to prevent or relieve nausea and vomiting. Not eating before your treatment may help relieve vomiting. Changes in diet such as eating several small meals or limiting activity may help lessen some of these effects. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Mild diarrhea is also a common side effect. However, diarrhea can rarely become severe, causing very serious problems due to dehydration. Tell your doctor right away if you develop: diarrhea that is severe or doesn't stop, abdominal or stomach pain/cramping, or blood/mucus in your stool.

Temporary hair loss may occur. Normal hair growth should return after treatment has ended.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Hand and foot problems sometimes occur with fluorouracil use. You can prevent or reduce these problems by protecting your hands and feet from a great deal of heat or pressure. For example, avoid taking hot baths/showers, handwashing dishes with hot water, taking long walks, and rubbing your hands/feet. Tell your doctor right away if you develop the following symptoms on your hands/feet: redness, peeling skin, blisters, pain, numbness, tingling, or swelling. If you develop these symptoms, consult your doctor for treatment options (such as reducing your dose or stopping fluorouracil therapy, applying ice packs to the hands/feet).

Tell your doctor right away if you have any serious side effects, including: headache, mental/mood changes (such as confusion), vision changes, unusual eye movements, loss of coordination, unusual tiredness.

Get medical help right away if you have any very serious side effects, including: easy bruising/bleeding, blood in the urine, black/bloody stools, vomit that looks like coffee grounds, stomach/abdominal pain, chest pain, jaw/left arm pain, fast/slow/irregular heartbeat, mouth sores, sore throat, painful swallowing, heartburn, pain/redness/swelling of the arms/legs.

This medication can lower the body's ability to fight an infection. Tell your doctor right away if you develop any signs of an infection (such as sore throat that doesn't go away, fever, chills).

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

Fluorouracil can commonly cause a rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe reaction. Get medical help right away if you develop a rash.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Precautions

Before using fluorouracil, tell your doctor or pharmacist if you are allergic to it; or to flucytosine; or to capecitabine; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: poor nutrition, decreased bone marrow function/blood cell disorders (such as anemia, leukopenia, thrombocytopenia), a certain enzyme deficiency (dihydropyrimidine dehydrogenase - DPD), a serious infection, liver problems, kidney problems.

Tell your health care professional that you are using fluorouracil before having any immunizations/vaccinations. Avoid contact with people who have recently received live vaccines (such as flu vaccine inhaled through the nose).

To lower the chance of getting cut, bruised, or injured, use caution with sharp objects like razors and nail cutters, and avoid activities such as contact sports.

This medication may make you more sensitive to the sun. Limit your time in the sun. Avoid tanning booths and sunlamps. Use sunscreen and wear protective clothing when outdoors. Tell your doctor right away if you get sunburned or have skin blisters/redness.

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using fluorouracil. Fluorouracil may harm an unborn baby. Men and women using this medication should ask about reliable forms of birth control during treatment and for some time after the last dose. If you or your partner becomes pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this drug passes into breast milk. Because of the possible risk to the infant, breastfeeding is not recommended while using this drug. Consult your doctor before breastfeeding.

Medical Alert

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).

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RxAnswers™ is a copyrighted combined product from TraceGains and First DataBank, Inc.

Drug information is selected from data included with permission and copyrighted by First DataBank, Inc. This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your healthcare professional. Always seek the advice of your healthcare professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your healthcare professional. This information does not contain any assurances that this product is safe, effective or appropriate for you.

This information is intended only for residents of the United States. Products sold under the same brand names in other countries may contain different ingredients.

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Information expires December 2025.