Fluorouracil (5-FU)

Pronunciation: flor-oh-YOOR-a-sil.

Generic name
fluorouracil
Drug class
Antineoplastic antimetabolite (pyrimidine analogue) -- systemic chemotherapy form; topical antimetabolite/keratolytic -- topical cream form
Form
Systemic: solution for injection/infusion (e.g. 25 mg/mL, 50 mg/mL). Topical: cream or solution (0.5% to 5% strength depending on brand/market).
Route
TWO DISTINCT ROUTES: (1) intravenous or intra-arterial injection/infusion (systemic chemotherapy); (2) topical application to the skin (cream/solution for actinic keratosis and superficial skin cancer). These are different products for different conditions, not interchangeable forms of the same treatment.
Legal status
Prescription-only in all markets reviewed. The systemic (injectable) form is administered only in a hospital/oncology setting; the topical cream form is prescription-only but self-applied at home under medical supervision.

Availability and supply rules vary by country

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: Efudix (fluorouracil 5% w/w cream) (7), Fluorouracil Ebewe / Alphapharm / Mylan / Agila / Intas / Accord (injection, generics) (7) · Full directory

What fluorouracil is and how it works

Fluorouracil (5-FU) is used as two genuinely different products. As a systemic chemotherapy medicine given by injection or infusion into a vein or artery, it treats certain cancers (colorectal, breast, stomach, and pancreatic cancer), working throughout the body to slow or stop cancer cell growth. As a separate topical cream or solution applied directly to the skin, it treats actinic keratosis (precancerous skin patches) and some superficial skin cancers, working locally on treated skin only. These are not the same treatment and are used for entirely different medical situations. (1) (4)

If you are receiving fluorouracil by injection or infusion for cancer treatment, your care team will usually check for a genetic condition called DPD deficiency before you start, because people who completely lack this enzyme can have severe, sometimes life-threatening reactions to the systemic medicine. If you have been prescribed fluorouracil cream for a skin condition, the main things to expect are a strong, visible skin reaction (redness, peeling, soreness) at the treated area during the course of treatment, and the need to avoid sun exposure on treated skin.

Mechanism of action: how fluorouracil works

Fluorouracil is a pyrimidine analogue antimetabolite that is converted intracellularly to active metabolites which inhibit thymidylate synthase, disrupting DNA synthesis, and are also incorporated into RNA, disrupting RNA processing/function -- effects most pronounced in rapidly dividing cells (tumor cells systemically; hyperproliferative/dysplastic keratinocytes topically). DPD is the rate-limiting enzyme that catabolises (breaks down) more than 80% of administered fluorouracil; its deficiency causes markedly increased systemic exposure and toxicity risk. (1) (2)

What fluorouracil is used for

Systemic (IV/infusion) form -- colorectal and breast cancer

Used by injection or infusion, alone or combined with other chemotherapy medicines, in the palliative management of colon, rectal, and breast cancer. (2)

Systemic (IV/infusion) form -- gastric and pancreatic cancer

Also used by injection or infusion for gastric (stomach) and pancreatic adenocarcinoma. (1)

Topical cream form -- actinic keratosis

Applied directly to the skin to treat actinic (solar) keratosis -- precancerous skin patches caused by sun damage. (4) (5)

Topical cream form -- superficial basal-cell carcinoma and other superficial skin lesions

Also used topically for superficial basal-cell carcinoma and, in the UK, for keratoacanthoma, Bowen's disease, and arsenical keratoses when other treatments are not suitable. (4)

Before taking fluorouracil

Do not take / not appropriate for

  • SYSTEMIC (injectable) form: must not be given to anyone with known complete dihydropyrimidine dehydrogenase (DPD) deficiency -- an absolute contraindication in the UK/EU product information, reflecting a real risk of life-threatening or fatal toxicity in this group. (United Kingdom, European Union) (2)
  • SYSTEMIC (injectable) form: the US label directs testing for DPYD genetic variants before starting (unless immediate treatment is necessary) and avoiding use in patients with certain homozygous/compound heterozygous DPYD variants causing complete DPD deficiency. (United States) (1)
  • TOPICAL cream form: do not use together with the antiviral medicines brivudine or sorivudine (or their close analogues) -- a specific, serious drug interaction distinct from the systemic form's DPD warning. (all countries) (4)
  • Neither form should be used in pregnancy; the topical cream is also contraindicated in breastfeeding, and the systemic form is contraindicated in breastfeeding. (all countries) (4) (2)

Tell your clinician about

  • For the systemic (injectable) form: any known or suspected DPD enzyme deficiency, any prior severe reaction to fluorouracil or capecitabine, heart problems (angina, prior heart attack, arrhythmia), and all other medicines, especially warfarin (increased bleeding/INR risk).
  • For the topical cream form: any current use of brivudine or sorivudine, any plan for significant sun/UV exposure during treatment, and whether you are pregnant, planning pregnancy, or breastfeeding.
  • For both forms: whether you could be pregnant or are breastfeeding, since both forms are contraindicated in these situations.
(1) (2) (4)

How to take fluorouracil

  • SYSTEMIC (injectable) form: given only by a healthcare professional, as an intravenous or intra-arterial injection or infusion, in a hospital or specialist oncology setting. Your care team will typically test for DPD deficiency beforehand and select your dose and schedule based on your cancer, other medicines, and DPD test result.
  • TOPICAL cream form: applied by the patient at home, thinly, to the affected skin area, once or twice daily depending on the specific product and market -- follow your own product's label exactly, since strength and frequency genuinely differ (e.g. a lower-strength 0.5% US product applied once daily for up to 4 weeks, versus a higher-strength 4-5% UK product applied once or twice daily for 3-4 weeks). Wash hands after application unless the hands are the treated area.
  • Do not apply the topical cream to a larger area than your product's label specifies (the UK product specifies no more than 500 cm2 at any one time).
(2) (4)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6) (7) (8)

Missed dose

Systemic (injectable) form: doses are scheduled and administered by your oncology team, who will manage any missed or delayed dose directly as part of your treatment plan. Topical cream form: if you miss an application, simply apply your next dose at the usual time -- do not apply extra cream to make up for a missed application.

Overdose

Systemic (injectable) form: administered by healthcare professionals under close monitoring; any concern about an incorrect dose is identified and managed by the treating team immediately, given the real risk of severe toxicity. Topical cream form: if a large amount is accidentally swallowed, or applied to a much larger skin area than directed, contact a doctor, pharmacist, or poison control promptly. (2)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Systemic form: nausea, vomiting, diarrhea, mouth sores (mucositis), hair thinning, and changes in blood counts.

What to notice: Systemic form: nausea, vomiting, diarrhea, mouth sores (mucositis), hair thinning, and changes in blood counts.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Topical cream form: intense redness (erythema), skin erosion, and pain or burning at the treated site -- this is an expected, visible part of how the treatment works, not necessarily a sign something is wrong, but should still be discussed with your prescriber.

What to notice: Topical cream form: intense redness (erythema), skin erosion, and pain or burning at the treated site -- this is an expected, visible part of how the treatment works, not necessarily a sign something is wrong, but should still be discussed with your prescriber.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (4)

Serious warnings

DPD (dihydropyrimidine dehydrogenase) deficiency toxicity -- SYSTEMIC form — emergency

Symptoms: Severe or unusually early/intense mucositis, diarrhea, low blood counts (infection, bruising, bleeding), or neurological symptoms following the start of treatment.

Action: This is a real, serious, well-documented risk -- your care team will typically test for DPD deficiency before your first dose. People with complete DPD deficiency must not receive this systemic medicine (an absolute contraindication in the UK/EU information; the US label directs avoiding use in this group and testing before starting). Report any severe or rapidly worsening symptoms during treatment to your care team immediately. (1) (2) (3)

Cardiotoxicity -- SYSTEMIC form — emergency

Symptoms: Chest pain, irregular heartbeat, or signs of heart failure (shortness of breath, swelling).

Action: Get emergency medical help immediately -- cardiotoxicity including heart attack, arrhythmia, and sudden cardiac death has been reported, especially with continuous infusion. (2) (1)

Hyperammonemic encephalopathy and neurologic toxicity -- SYSTEMIC form — emergency

Symptoms: Confusion, altered mental status, disorientation, coma, or difficulty with coordination (ataxia), typically within about 72 hours of a dose.

Action: Get emergency medical help immediately -- your care team will withhold further doses and may start ammonia-lowering treatment if this occurs. (1)

Severe myelosuppression (low blood counts) -- SYSTEMIC form — high caution

Symptoms: Signs of infection (fever), unusual bruising or bleeding.

Action: Your care team monitors blood counts regularly during treatment (leukopenia is expected around days 7-14); your care team will withhold your dose or reduce your dose if counts fall too low. Report fever or unusual bleeding/bruising promptly. (2)

Severe mucositis or gastrointestinal bleeding -- SYSTEMIC form — high caution

Symptoms: Mouth ulcers/sores, severe diarrhea, or blood in stool.

Action: Tell your care team promptly -- treatment is stopped at the first sign of oral ulceration or gastrointestinal bleeding. (2)

Severe local skin reaction -- TOPICAL cream form — high caution

Symptoms: Intense redness, blistering, ulceration, or significant pain beyond what your prescriber described as expected.

Action: Some visible skin reaction is an expected part of topical treatment, but tell your prescriber if the reaction seems more severe than expected, does not improve after stopping treatment, or is accompanied by signs of infection. (4)

Fire hazard from treated fabric -- TOPICAL cream form — high caution

Symptoms: Not applicable -- this is a physical/fire-safety hazard rather than a body symptom.

Action: Fabric (clothing, bedding, dressings) that has been in contact with this cream burns more easily. Keep treated fabric away from open flames or sources of ignition, and follow your product's specific disposal/laundering guidance. (4)

Interactions

  • SYSTEMIC form: warfarin -- fluorouracil can increase warfarin's anticoagulant effect; INR should be monitored closely. (1)
  • TOPICAL cream form: brivudine, sorivudine, and related antiviral nucleoside analogues -- a specific, serious contraindicated combination distinct from any systemic interaction. (4)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Both the systemic and topical forms are contraindicated in pregnancy. The systemic form carries a real embryofetal toxicity risk, and effective contraception is required during treatment and for at least 6 months afterward per the UK product information. (1) (2) (3) (4) (5) (6) (7) (8)

Children

The topical cream is not recommended for children per the UK product information. The systemic form's use in children is a specialist oncology decision outside the scope of this general reference page. (1) (2) (3) (4) (5) (6) (7) (8)

Elderly

No separate systemic-form dose adjustment based on age alone was identified in the sources reviewed beyond the general individualization already required for all patients; older adults may be more susceptible to cardiotoxicity and myelosuppression. (1) (2) (3) (4) (5) (6) (7) (8)

Renal Impairment

No specific regulator-reviewed renal-impairment dosing guidance for either form was identified in the sources reviewed for this dossier; systemic-form dosing is individualized by the treating oncology team regardless. (1) (2) (3) (4) (5) (6) (7) (8)

Monitoring

Before starting

  • SYSTEMIC form: DPD deficiency testing (phenotype and/or genotype) before the first dose, per UK/EU guidance and recommended on the US label.
  • SYSTEMIC form: baseline blood counts and cardiac risk assessment.
  • TOPICAL form: confirm no current brivudine/sorivudine use and discuss sun-exposure planning.

During treatment

  • SYSTEMIC form: regular blood counts (leukopenia expected around days 7-14), cardiac monitoring, and prompt assessment of any neurological or mucosal symptoms.
  • TOPICAL form: monitoring of the treated skin area for expected versus excessive reaction, and avoidance of UV/sun exposure on treated skin.
(2) (4)

Storage

Systemic (injectable) form: stored and handled by pharmacy/hospital staff under controlled conditions, not self-stored by patients. Topical cream form: store as directed on your product's own packaging, out of reach of children, and away from heat sources given the fire-hazard warning for contaminated fabric.

Professional information

Clinician-facing context only, sourced from the current US DailyMed label, UK EMC SmPCs (both the injectable and 5% cream products), and the EMA's own DPD-testing referral/binding-decision page; verify against the current full label before prescribing.

United States, United Kingdom, European Union, Canada, Australia, New Zealand

Indication: Systemic: colorectal, breast, gastric, and pancreatic adenocarcinoma (individualized dosing, regimen-dependent).

Dose summary: No fixed standard dose -- individualized by tumor type, regimen, DPD status, and tolerability. Daily infusion typically 30-60 minutes or continuous 24-hour infusion per the UK SmPC, repeated until toxicity or a total cumulative dose threshold.

Renal context: No specific regulator-reviewed renal dose adjustment identified in the sources reviewed; dosing is individualized regardless. (2) (1)

United Kingdom, United States

Indication: Topical: actinic keratosis and superficial basal-cell carcinoma.

Dose summary: UK Efudix 5% cream: thin layer once or twice daily, 3-4 weeks, max 500 cm2 treated area at a time. US Carac 0.5% cream: once daily to face/scalp, up to 4 weeks.

Renal context: Not applicable to the topical form. (4) (5)

Mechanism of action

Hepatic guidance

No specific regulator-reviewed hepatic-impairment dose adjustment for either form was identified in the sources reviewed for this dossier.

Overdose note

Systemic overdose management is supportive, with close monitoring of blood counts, cardiac status, and neurological status; there is no specific antidote. Topical overexposure (accidental ingestion or excessive application) should be assessed by a poison control centre or clinician given the same active ingredient's systemic toxicity potential, particularly relevant in DPD-deficient individuals. (1) (2)

Frequently asked questions

Is fluorouracil chemotherapy the same as fluorouracil cream?

No -- these are two genuinely different products, not two forms of the same treatment. The injectable/infusion form is systemic chemotherapy for certain internal cancers (colorectal, breast, gastric, pancreatic), working throughout the body. The cream is applied only to the skin for actinic keratosis or superficial skin cancer, working locally. Their risks, dosing, and monitoring are different, though both use the same active ingredient and both are affected by DPD enzyme status. (1) (4)

What is DPD deficiency and why does it matter for fluorouracil?

DPD (dihydropyrimidine dehydrogenase) is the enzyme that breaks down more than 80% of fluorouracil in the body. People who completely lack this enzyme (an estimated 0.01-0.5% of the Caucasian population, per the UK SmPC) can experience severe or fatal toxicity from the systemic (injectable) form, which is why UK/EU product information makes complete DPD deficiency an absolute contraindication, and the US FDA label carries a boxed warning recommending DPYD genetic testing before starting treatment (unless immediate treatment is necessary). This is a real, dated regulatory action: the European Medicines Agency formally recommended DPD testing on 30 April 2020, becoming legally binding across the EU in July 2020. DPD status is also noted as relevant to systemic toxicity risk with the topical cream, though to a lesser degree given its localised application. (1) (2) (3)

Why does my fluorouracil cream make my skin look worse before it gets better?

Intense redness, erosion, and soreness during treatment are an expected part of how the topical cream works on precancerous or abnormal skin cells, not necessarily a sign of a problem. Still, tell your prescriber if the reaction seems unusually severe, doesn't settle after finishing treatment, or looks infected. (4)

Can I use fluorouracil cream if I'm taking an antiviral medicine?

Not if that medicine is brivudine or sorivudine (or a closely related antiviral nucleoside analogue) -- this combination is specifically contraindicated with topical fluorouracil. Tell your prescriber about all medicines you are taking, including antivirals, before starting the cream. (4)

What is the mechanism of action of fluorouracil?

Fluorouracil is a pyrimidine analogue antimetabolite that is converted intracellularly to active metabolites which inhibit thymidylate synthase, disrupting DNA synthesis, and are also incorporated into RNA, disrupting RNA processing/function -- effects most pronounced in rapidly dividing cells (tumor cells systemically; hyperproliferative/dysplastic keratinocytes topically). DPD is the rate-limiting enzyme that catabolises (breaks down) more than 80% of administered fluorouracil; its deficiency causes markedly increased systemic exposure and toxicity risk. (1) (2)

What is the generic name of Fluorouracil (5-FU)?

The generic name is fluorouracil. (1) (4)

What class of drug is fluorouracil?

Fluorouracil (5-FU) is classed as: Antineoplastic antimetabolite (pyrimidine analogue) -- systemic chemotherapy form; topical antimetabolite/keratolytic -- topical cream form. (1) (4)

References

  1. FLUOROURACIL injection, solution -- full prescribing informationDailyMed (U.S. National Library of Medicine) -- FDA-approved prescribing information · United States · accessed 2026-07-30 · source 1
  2. Fluorouracil injection 50 mg/ml, solution for injection -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- medac Pharma LLP · United Kingdom · accessed 2026-07-30 · source 2
  3. Fluorouracil and fluorouracil related substances (capecitabine, tegafur and flucytosine) containing medicinal products -- referral; EMA recommendations on DPD testingEuropean Medicines Agency (EMA) -- PRAC/CHMP referral procedure and formal recommendation · European Union · accessed 2026-07-30 · source 3
  4. Fluorouracil 5% Cream (Efudix) -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- Viatris Products Limited · United Kingdom · accessed 2026-07-30 · source 4
  5. Carac (fluorouracil cream, 0.5%) -- prescribing information; topical fluorouracil brand overviewU.S. FDA-approved prescribing information (accessdata.fda.gov) and corroborating secondary clinical sources · United States · accessed 2026-07-30 · source 5
  6. Adrucil (fluorouracil injection) and Efudex (fluorouracil 5% topical cream) -- Canadian marketed productsHealth Canada Drug Product Database (DPD) plus Canadian oncology/hospital drug monographs (BC Cancer, Cancer Care Ontario) and manufacturer product monograph · Canada · accessed 2026-07-30 · source 6
  7. EFUDIX (fluorouracil 5% w/w cream) and multiple FLUOROURACIL injection products -- ARTG registrationsTherapeutic Goods Administration (TGA), Australia -- Australian Register of Therapeutic Goods (ARTG) entries · Australia · accessed 2026-07-30 · source 7
  8. Efudix cream and Fluorouracil Accord injection -- New Zealand Data SheetsMedsafe (New Zealand regulator) -- New Zealand Data Sheets · New Zealand · accessed 2026-07-30 · source 8

Brand names by country

Single-ingredient fluorouracil names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • FAVLYXA25 mg/mL · avyxa pharma, llc
  • TOLAK.04 g/g · hill dermaceuticals, inc.
  • Efudex2 g/40g · bausch health us, llc

United Kingdom

  • Fluorouracil Injection (medac) (2)MHRA licensed emc smpc confirmed · 25 mg/mL, 50 mg/mL · medac Pharma LLP
  • Efudix (fluorouracil 5% cream) (4)MHRA licensed emc smpc confirmed · 5% w/w · Viatris Products Limited

Canada

  • EFUDEX CRM

Australia

  • Efudix (fluorouracil 5% w/w cream) (7)TGA ARTG 13721 confirmed · 5% w/w · iNova Pharmaceuticals (Australia) Pty Ltd
  • Fluorouracil Ebewe / Alphapharm / Mylan / Agila / Intas / Accord (injection, generics) (7)TGA ARTG registered confirmed · various, e.g. 50 mg/mL · Sandoz, MedTAS, Mylan, Agila, Intas, Accord

New Zealand

  • Efudix (topical cream) (8)medsafe datasheet and cmi existence confirmed · 5% w/w · Not independently confirmed in this review
  • Fluorouracil Accord (injection) (8)medsafe datasheet existence confirmed · per data sheet title · Accord Healthcare
View brands in additional countries.

European Union

Fluorouracil (national brand names, generic and Efudix-equivalent) (3)

This page covers two genuinely different fluorouracil products (systemic chemotherapy and topical skin cream) and is not a substitute for advice from the clinical team managing your specific treatment. All dosing, DPD-testing, and treatment decisions should be made with your treating specialist or prescriber.

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