Fluorouracil: uses, dosing, side effects & brands
Fluorouracil is a nucleoside metabolic inhibitor sold in the U.S. under 6 brand and generic names, for breast neoplasms, basal cell carcinoma and colonic neoplasms. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Nucleoside Metabolic Inhibitor
- Treats (across its forms)
- Breast Neoplasms, Basal Cell Carcinoma and Colonic Neoplasms
- Available as
- Topical · Injectable · Solution
- Sold as
- 6 products — Tolak, Adrucil and Efudex, and others
- Prescription?
- Prescription only
- Generic available?
- Yes
- What the pharmacy pays
- about $0.61 per ml — not your price
- Boxed warning
- Boxed warning
How Tolak is dosed
From the FDA label for Tolak (application NDA022259). Other fluorouracil products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
Prior to application of Tolak Cream, wash, rinse, and dry the treatment areas. Apply Tolak Cream once daily in an amount sufficient to cover the lesions of the face, ears, and/or scalp with a thin film, using the fingertips to gently massage the medication uniformly into the skin. Apply Tolak Cream for a period of 4 weeks as tolerated. Thoroughly wash hands following Tolak Cream application. Tolak Cream is for topical use only. Do not apply to eyes, nose, mouth or mucous membranes. Not for ophthalmic, oral or intravaginal use. Apply Tolak Cream after washing, rinsing, and drying the treatment area(s) ( 2 ). Apply Tolak Cream once daily in an amount sufficient to cover the lesions of the face, ears, and/or scalp with a thin film, using the fingertips to gently massage the medication uniformly into the skin ( 2 ). Tolak Cream should be applied for a period of 4 weeks as tolerated ( 2 ). Wash hands thoroughly following Tolak Cream application ( 2 ). Tolak Cream is for topical use only. Do not apply to eyes, nose, mouth or mucous membranes ( 2 ). Not for ophthalmic, oral, or intravaginal use ( 2 ).
Everything below is the FDA label for Tolak (topical). Fluorouracil is also sold as injectable and solution, and those are different medicines to take — follow the label for the one you were prescribed.
Tolak side effects
The following serious adverse reactions are discussed in more detail in other sections of the labeling: Application Site Adverse Reactions [see Warnings and Precautions (5.1) ] Hypersensitivity Reactions [see Warnings and Precautions (5.2) ] Ophthalmic Adverse Reactions [see Warnings and Precautions (5.3) ] Photosensitivity [see Warnings and Precautions (5.4) ] Embryofetal toxicity [see Warnings and Precautions (5.5) ] Toxicity in Patients with Dihydropyrimidine Dehydrogenase Deficiency [see Warnings and Precautions (5.6) ] The most common (incidence > 68%) adverse reactions occur at the application site and include erythema, scaling/dryness, crusting, pruritus, stinging/burning, edema, and erosions. Erythema is observed in 99% of patients with actinic keratosis treated with Tolak Cream ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Hill Dermaceuticals at 1-800-344-5707 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The data described below reflect exposure to Tolak Cream in 397 subjects with actinic keratosis in vehicle-controlled trials. The population ranged in age from…
Who shouldn’t take Tolak
Tolak Cream is contraindicated: During pregnancy [see Warnings and Precautions (5.5 , 8.1) ] In patients with dihydropyrimidine dehydrogenase (DPD) deficiency [see Warnings and Precautions (5.6) ] Pregnancy ( 4.1 , 8.1 ). Dihydropyrimidine dehydrogenase (DPD) deficiency ( 4.2 ). 4.1 Pregnancy Tolak Cream may cause fetal harm when administered during pregnancy and is contraindicated in women who are pregnant. If this drug is used during pregnancy, or if the patient becomes pregnant while using this drug, the patient should be apprised of the potential hazard to the fetus. 4.2 Dihydropyrimidine Dehydrogenase Deficiency Tolak Cream is contraindicated in patients with dihydropyrimidine dehydrogenase (DPD) deficiency.
Tolak drug interactions
Subjects using systemic steroids, immunosuppressants, and immunomodulators were generally excluded from the clinical studies of Tolak Cream, as were subjects who used retinoids, topical steroids, glycolic acid products, alpha-hydroxy products, and chemical peeling products in the treatment areas. No clinical trials were designed to specifically evaluate drug interactions.
Every fluorouracil product we track (6)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | 72/100 | Prescription | Topical | Generic | $1 | View → | |
| 2 | Not yet rated | Prescription | Injectable | Generic | $1 | View → | |
| 3 | Not yet rated | Prescription | Topical | Generic | $1 | View → | |
| 4 | Not yet rated | Prescription | Injectable | Generic | $1 | View → | |
| 5 | Not yet rated | Prescription | Topical | Generic | $1 | View → | |
| 6 | Not yet rated | Prescription | Topical | Generic | $1 | View → |
Fluorouracil and breastfeeding
From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.
Full LactMed record for fluorouracil: levels in milk, effects in breastfed infants, and the drugs it would consider insteadMost sources consider breastfeeding to be contraindicated during maternal antineoplastic drug therapy. It might be possible to breastfeed safely during intermittent therapy with an appropriate period of breastfeeding abstinence. The duration of abstinence is not clear, but some have suggested a period of 24 hours before resuming nursing, while others have used a 72-hour abstinence period safely. Limited information indicates that a maternal continuous intravenous fluorouracil infusion at a dose of 200 mg/square meter daily produces undetectable levels in milk. If fluorouracil use is undertaken, monitoring of the infant's complete blood count and differential is advisable. Chemotherapy may adversely affect the normal microbiome and chemical makeup of breastmilk. Women who receive chemotherapy during pregnancy are more likely to have difficulty nursing their infant.
National Institute of Child Health and Human Development, record revised July 15, 2026. LactMed states its information is not a substitute for professional judgement.
What people report to the FDA about fluorouracil
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 88,951 reports naming fluorouracil, and the FDA flagged 94% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- diarrhoea8,207 reports
- neutropenia6,119 reports
- nausea6,043 reports
- vomiting4,838 reports
- neuropathy peripheral3,849 reports
- fatigue3,784 reports
- pyrexia3,578 reports
- thrombocytopenia3,526 reports
Read these as a signal, not a rate. A report does not mean fluorouracil caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
Related calculators
Frequently asked questions
What is Tolak?
Tolak (Fluorouracil) is a nucleoside metabolic inhibitor used to treat Breast Neoplasms, Basal Cell Carcinoma, Colonic Neoplasms, Head and Neck Neoplasms.
What kind of drug is fluorouracil?
The FDA classifies fluorouracil as a nucleoside metabolic inhibitor. Nucleoside metabolic inhibitors are fake DNA building blocks that fast-dividing cancer cells mistake for the real thing. Once inside, they get incorporated into the cell's DNA and also block enzymes such as ribonucleotide reductase, which together halt DNA copying and cause the cancer cell to die. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take fluorouracil with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run fluorouracil against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is fluorouracil sold under?
We track 6 fluorouracil-containing products in the U.S.: Tolak, Adrucil, Efudex, Favlyxa, Fluoroplex and Fluorouracil. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does fluorouracil come in?
Across the brands we track, fluorouracil is currently marketed as topical, injectable and solution, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic fluorouracil?
Yes. Our catalog lists 1 generic fluorouracil product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Fluorouracil: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/fluorouracil
- MLA
- “Fluorouracil: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/fluorouracil.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for fluorouracil on DailyMed (NIH) ↗ — including its boxed warning in full.