Generic Fluorouracil

Common use
Fluorouracil is an antimetabolite used to treat various types of cancer, including colorectal, breast, stomach, pancreatic, and skin cancers. It interferes with the synthesis of DNA and RNA in cancer cells, preventing their growth and replication. It is commonly administered as an intravenous injection or as a topical cream for skin lesions. This medication is typically used in combination with other cancer treatments.

Dosage and direction
The dosage and administration of fluorouracil depend on the type and stage of cancer, the route of administration, and the patient's body surface area. It is usually given in cycles to allow the body time to recover between treatments. Topical formulations should be applied exactly as prescribed to the affected area. Never adjust your dose without medical supervision.

Precautions
Before using fluorouracil, inform your doctor if you have bone marrow suppression, active infections, liver dysfunction, or dihydropyrimidine dehydrogenase (DPD) deficiency. The drug can cause serious side effects such as immunosuppression and gastrointestinal toxicity. Avoid contact with people who are sick or recently received live vaccines. Use sun protection, especially when using topical fluorouracil, as it may increase skin sensitivity.

Contraindications
Fluorouracil is contraindicated in patients with known hypersensitivity to the drug, marked bone marrow suppression, or severe infections. It should not be used in individuals with DPD enzyme deficiency, as it may cause life-threatening toxicity. Topical use is not recommended on open wounds or mucous membranes. Use in pregnancy is contraindicated due to potential harm to the fetus.

Possible side effect
Common side effects include nausea, vomiting, diarrhea, mouth sores, and fatigue. Skin reactions such as redness, peeling, or irritation may occur with topical use. Serious side effects include bone marrow suppression, heart toxicity, and severe gastrointestinal damage. Immediate medical help is necessary if signs of infection, chest pain, or unusual bleeding occur.

Drug interaction
Fluorouracil may interact with medications such as warfarin, phenytoin, and other chemotherapy drugs, increasing the risk of side effects. It can also affect blood counts and liver enzyme levels. Avoid live vaccines during treatment due to immunosuppression. Always inform your doctor about all other medications, supplements, and herbal products you are using.

Missed dose
If a scheduled intravenous dose is missed, contact your healthcare provider immediately for instructions. Do not attempt to take double doses. For topical use, apply the missed dose as soon as you remember unless it is close to the next application. Follow your treatment plan closely for best results.

Overdose
Symptoms of overdose may include severe nausea, vomiting, bleeding, infection, and mouth sores. Overdose can be life-threatening and requires immediate medical attention. Treatment may involve hospitalization and supportive care, including blood transfusions. There is no specific antidote, but uridine triacetate may be used in severe toxicity cases.

Storage
Store fluorouracil injection as directed by your healthcare provider, usually in a refrigerated setting. Topical formulations should be stored at room temperature, away from heat and light. Keep out of reach of children and pets. Do not use after the expiration date or if the product changes color or consistency.

Disclaimer

We provide only general information about medications which does not cover all directions, possible drug integrations, or precautions. Information at the site cannot be used for self-treatment and self-diagnosis. Any specific instructions for a particular patient should be agreed with your health care adviser or doctor in charge of the case. We disclaim reliability of this information and mistakes it could contain. We are not responsible for any direct, indirect, special or other indirect damage as a result of any use of the information on this site and also for consequences of self-treatment.

Clinical Verification

Last Clinically Updated: August 15, 2026

Written By

Dr. Elena Vance, PharmD

Clinical Specialist in Neuropharmacology

Fact Checked By

Marcus Thorne, MS

Biomedical Data & FDA Label Verification

Medically Reviewed By

Dr. Arthur Campbell, MD

Board-Certified Psychiatrist (ABPN)