Fluorouracil
Fluorouracil is an antimetabolite chemotherapy medication used to treat various cancers including colorectal, breast, gastric, pancreatic, and certain skin cancers. It works by interfering with DNA and RNA synthesis in rapidly dividing cells, ultimately inhibiting cell growth and reproduction.
Fluorouracil is a chemotherapy drug that inhibits cancer cell growth by disrupting DNA and RNA synthesis.
Key facts at a glance
- ATC
- L01BC02
- RxNorm
- 4492
- Generic
- Fluorouracil
- Class
- atc-l01
- Brands
- Tolak, Adrucil, Fluoroplex, Efudex, Favlyxa, Carac
- Availability
- rx
- Lactation
- unknown
- Routes
- topical, oral
- Forms
- injection, cream, solution, capsule
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 500mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 250mg twice daily
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 400mg daily
- Maximum
- consult physician
- Frequency
- once daily
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
10 groupspregnancy
first trimesteravoid
avoid use during pregnancy unless benefits outweigh risks to the mother outweigh potential harm to fetus
regular fetal monitoring and ultrasound examinations
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
second trimesteravoid
avoid use during pregnancy unless benefits outweigh risks
regular fetal monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
third trimesteravoid
avoid use near term due to risk of fetal toxicity and complications
fetal monitoring and assessment of fetal growth
Use of this medication in this population requires careful consideration of risks and benefits.
lactation
breastfeedingdiscontinue breastfeeding
do not breastfeed during treatment and for at least 1 week after last dose
not applicable
Use of this medication in this population requires careful consideration of risks and benefits.
geriatric
elderlyconsider dose reduction based on organ function
use with caution due to potential decreased hepatic and renal function; monitor for adverse effects
regular monitoring of renal and hepatic function, complete blood counts
Use with caution and monitor for adverse effects.
pediatric_age
children adolescentsweight-based dosing with careful monitoring
used in pediatric oncology; dosing based on body surface area; requires specialized pediatric oncology management
frequent complete blood counts, liver function tests, and close monitoring for toxicity
Use with caution and monitor for adverse effects.
renal_impairment
mild to moderateno standard dose reduction; monitor closely
use with caution; fluorouracil is primarily metabolized hepatically but monitor renal function
monitor renal function and adjust dose based on toxicity
Use with caution and monitor for adverse effects.
renal_impairment
severeconsider dose reduction
use with caution in severe renal impairment; consider dose reduction and close monitoring
frequent monitoring of renal function and blood counts
Use with caution and monitor for adverse effects.
hepatic_impairment
mildno standard dose adjustment; monitor closely
use with caution; fluorouracil is extensively metabolized in liver
monitor liver function tests and for signs of hepatotoxicity
Use with caution and monitor for adverse effects.
hepatic_impairment
moderate to severesignificant dose reduction or avoid
use with extreme caution or avoid in moderate to severe hepatic impairment due to altered metabolism
frequent liver function monitoring, bilirubin, and clinical assessment
Use of this medication in this population requires careful consideration of risks and benefits.
Statistics and clinical data
Commonly prescribed since
General prescribing information
Drug class
Drug class information
Common uses
Common therapeutic uses
Mechanism of action
Pharmacological mechanism
Treats colorectal cancer (often with leucovorin), breast cancer, gastric cancer, pancreatic cancer, and topical forms are used for actinic keratosis and superficial basal cell carcinoma.
Fluorouracil is converted to active metabolites that inhibit thymidylate synthase, blocking DNA synthesis. It is also incorporated into RNA and DNA, causing cell death in rapidly dividing cancer cells.
Can cause significant bone marrow suppression, mucositis, nausea, diarrhea, and hand-foot syndrome. Topical use may cause local skin reactions. Contraindicated in pregnancy (Category D) and in patients with known dihydropyrimidine dehydrogenase (DPD) deficiency. Requires regular blood count monitoring during treatment.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 24, 2026. · Read our editorial policy