Updated: January 11, 2026

What Is Fluorouracil? Uses, Dosage, and What You Need to Know in 2026

Author

Peter Daggett

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Brand Names and Generic Name
What Is Fluorouracil Used For?
Cancer Treatment (IV Injection)
Skin Conditions (Topical Cream)
How Is Fluorouracil Given?
What Are the Typical Doses?
Is Fluorouracil a Controlled Substance?
Key Safety Information for 2026

Fluorouracil (5-FU) is a chemotherapy drug used for colorectal, gastric, breast, and pancreatic cancers — and topically for skin conditions. Here's a complete patient guide.

Fluorouracil — commonly called 5-FU or 5-fluorouracil — is one of the most widely used chemotherapy drugs in the world. It has been in use since 1962 and remains a cornerstone of treatment for several types of cancer. It also has important uses in dermatology for treating precancerous and cancerous skin conditions. This guide explains what fluorouracil is, what it's used for, how it's given, and what patients need to know in 2026.

Brand Names and Generic Name

Fluorouracil is the generic name for this drug. Brand names include:

Adrucil — the injectable formulation used in chemotherapy.

Efudex — 5% topical cream/solution for skin conditions.

Carac — 0.5% topical cream for actinic keratosis.

Tolak — 4% topical cream for actinic keratosis.

What Is Fluorouracil Used For?

Fluorouracil is FDA-approved for two broad categories of use:

Cancer Treatment (IV Injection)

Colorectal adenocarcinoma (colon and rectal cancer) — first-line in FOLFOX, FOLFIRI, and other regimens.

Gastric adenocarcinoma (stomach cancer).

Pancreatic adenocarcinoma — part of FOLFIRINOX.

Breast adenocarcinoma — used in CMF and other regimens.

Off-label uses include anal carcinoma, esophageal cancer, cervical cancer, advanced biliary tract cancer, and head and neck squamous cell carcinomas.

Skin Conditions (Topical Cream)

Actinic keratoses (AK) — precancerous rough patches caused by sun damage.

Superficial basal cell carcinoma (sBCC) — a type of skin cancer where surgery or other methods are not feasible.

How Is Fluorouracil Given?

The way fluorouracil is given depends entirely on what condition is being treated:

IV bolus: Rapid injection over approximately 15 minutes. Used in some regimens.

Continuous IV infusion: Infused over 46-48 hours via a portable pump (most common in FOLFOX/FOLFIRI). Patients wear a small pump and return to the clinic to have it disconnected.

Topical cream: Applied once or twice daily to affected skin areas for 2-6 weeks depending on the indication.

What Are the Typical Doses?

Doses vary significantly by indication and regimen. Your oncologist will calculate doses based on your body surface area (BSA) and treatment protocol. Common examples include:

FOLFOX (colorectal cancer): 400 mg/m2 IV bolus on Day 1, then 2,400-3,000 mg/m2 over 46-hour continuous infusion every 2 weeks.

Breast cancer (adjuvant): 500-600 mg/m2 IV on Days 1 and 8 of a 28-day cycle.

Topical (actinic keratosis): Apply a small amount to affected areas once or twice daily for 2-4 weeks. Your skin may look worse before it looks better — this is expected.

Is Fluorouracil a Controlled Substance?

No. Fluorouracil is not a DEA-scheduled controlled substance. It requires a prescription but has no special prescribing restrictions beyond a standard prescription. There are no refill limitations tied to scheduling.

Key Safety Information for 2026

Two critical safety updates for 2026:

DPYD genetic testing: In February 2026, the FDA updated labeling for fluorouracil and capecitabine to more strongly recommend DPYD gene testing before starting treatment. Patients with DPD deficiency face severe or fatal toxicity risk. Ask your doctor about testing.

Drug shortage: Fluorouracil injection has been in shortage since 2023. If you are starting or continuing fluorouracil, confirm availability with your pharmacy or infusion center well in advance of your treatment date.

To understand how fluorouracil works in the body, see our guide on how fluorouracil's mechanism of action. If you need help finding fluorouracil in stock at a pharmacy near you, medfinder can help.

Frequently Asked Questions

Fluorouracil is FDA-approved for colorectal adenocarcinoma, gastric adenocarcinoma, pancreatic adenocarcinoma, and breast adenocarcinoma when given by IV injection. Off-label uses include anal carcinoma, esophageal cancer, cervical cancer, biliary tract cancer, and head and neck cancers.

This depends on your regimen and cancer type. In FOLFOX for colorectal cancer, cycles are every 2 weeks and may continue for 6-12 months or more. Your oncologist will determine the duration based on your response to treatment and tolerance. Each cycle typically involves a 46-48 hour continuous infusion with a portable pump.

They contain the same active ingredient (fluorouracil) but are very different products. Topical fluorouracil cream works locally on the skin with minimal systemic absorption (typically under 6%). IV fluorouracil enters the bloodstream and affects rapidly dividing cells throughout the body. They are not interchangeable.

Capecitabine (Xeloda) is an oral tablet that is converted to fluorouracil in the body. Fluorouracil itself must be given intravenously. Capecitabine is more convenient but carries the same DPD deficiency risk. For some cancer types and regimens, they are considered equivalent — but this is a clinical decision made by your oncologist.

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