fluorouracil at a glance
Medicine class
Fluoropyrimidine antimetabolite and cytotoxic treatment.
Available forms
Hospital-administered injection or infusion, and prescription skin cream.
Key safety check
DPD deficiency testing is required before intravenous treatment because deficiency can cause severe or fatal toxicity. Routine testing is not required before topical treatment.
What is fluorouracil used for?
Different formulations are licensed for different purposes:
Injections may be used alone or with other treatments for common cancers, particularly colon and breast cancer.
Tolak cream treats non-thickened actinic keratosis on the face, ears or scalp in adults.
How does fluorouracil work?
Fluorouracil is converted into active compounds that block thymidylate synthase, impair DNA formation and disrupt RNA. Rapidly dividing cancerous or precancerous cells are particularly affected. DPD is the main enzyme that breaks fluorouracil down, so reduced DPD activity increases systemic exposure and toxicity.
fluorouracil preparations and strengths
Cream
Route: Cutaneous
Strengths: 40 mg/g, 5%
Injection
Route: Parenteral
Strengths: 25 mg/mL, 50 mg/mL
How to take fluorouracil
Systemic fluorouracil is prepared and administered by trained cancer-care professionals. Use Tolak cream only on the prescribed skin area and follow its label.
Wash, rinse and gently dry the treatment area before applying a thin film.
Avoid the eyes, mouth, nose, other mucous membranes, open wounds and damaged skin.
Wash your hands thoroughly afterwards and avoid transferring cream to another person.
Do not cover the area unless specifically instructed, as this can intensify inflammation.
Avoid sunlight, sunlamps and tanning beds during topical treatment.
fluorouracil side effects
Common or expected effects
- Systemic treatment: nausea, vomiting, diarrhoea, sore mouth, reduced blood-cell counts, infection risk, weakness, hair loss and hand-foot skin reactions.
- Topical treatment: redness, inflammation, dryness, scaling, itching, burning, swelling, crusting or erosion. Some inflammation is expected as abnormal skin cells respond.
Get urgent medical advice
- Fever, chills or other infection signs during systemic treatment.
- Severe diarrhoea, persistent vomiting, extensive mouth ulcers or gastrointestinal bleeding.
- Chest pain, breathlessness, palpitations or fainting.
- Confusion, difficulty speaking or walking, seizures or marked weakness.
- Severe allergic reaction, extensive blistering or ulceration.
- Mouth sores, abdominal pain, diarrhoea, vomiting, fever or chills during topical treatment.
fluorouracil in pregnancy
Tolak must not be used during pregnancy. Systemic fluorouracil can harm a fetus and is considered during pregnancy only by a specialist when the potential benefit justifies the risk. Discuss pregnancy planning, contraception and fertility preservation with the treatment team beforehand.
fluorouracil while breastfeeding
Breastfeeding is contraindicated with Tolak and must stop during systemic fluorouracil treatment because risk to the infant cannot be excluded. Seek specialist advice before treatment.
fluorouracil interactions
The treatment team should review all prescribed, over-the-counter and complementary products.
Brivudine, sorivudine and related antivirals
They inhibit DPD and can cause potentially fatal toxicity. Concurrent use is contraindicated and separation is required.
Folinic acid or calcium folinate
May enhance fluorouracil activity but increase gastrointestinal and blood-related toxicity, requiring careful monitoring.
Common questions about fluorouracil
Answers are fully visible for fast scanning and source review.
Is fluorouracil chemotherapy?
Yes. It is a cytotoxic antimetabolite used systemically for cancer and topically against abnormal cells in actinic keratosis.
Why is DPD testing needed before systemic treatment?
DPD breaks fluorouracil down. Complete or partial deficiency can cause severe or fatal toxicity, so testing is required before intravenous treatment.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.