Fluorouracil – Simple Guide to Uses, Dosage & Safety

If you’ve heard the name fluorouracil (often called 5‑FU) and wonder what it really is, you’re in the right place. It’s a chemotherapy medicine that also shows up in creams for skin problems. Below we break down how it works, why doctors prescribe it, and what you should watch out for.

How Fluorouracil Works

Fluorouracil stops cells from making DNA and RNA properly. Fast‑growing cells – like cancer cells or overactive skin cells – get hit hardest. That’s why it’s used to treat cancers of the breast, colon, head and neck, plus actinic keratosis and some warts when applied as a cream.

When taken by mouth or through an IV, the drug spreads throughout your body. Topical creams stay on the skin and target only the treated area. This difference matters for side effects and how you feel during treatment.

Typical Dosage Forms

Doctors can give fluorouracil in three ways: oral tablets, intravenous infusion, or a prescription cream. The exact dose depends on the condition, your weight, kidney function and other meds you’re using. For skin lesions, the cream is usually applied once or twice daily for a few weeks.

IV infusions are often scheduled every one to two weeks in a clinic. Oral tablets might be taken daily for several months. Always follow the schedule your doctor writes – missing doses can reduce effectiveness, while extra doses raise toxicity risk.

Common Side Effects

Because fluorouracil hits fast‑growing cells, you may notice mouth sores, low white blood cell counts, or hair thinning. The skin cream can cause redness, swelling, and peeling where it’s applied. Most side effects are mild to moderate and improve after treatment ends.

If you develop fever, severe diarrhea, or sudden shortness of breath, call your doctor right away – these could be signs of a serious reaction. Regular blood tests help catch problems early when the drug is given systemically.

Practical Tips for Patients

Keep a medication diary: note each dose, time, and any symptoms you feel. This makes it easier to discuss issues with your healthcare team.

Stay hydrated, especially if you’re on IV or oral fluorouracil. Good hydration helps kidneys clear the drug and can lessen nausea.

If you use the topical cream, wash your hands thoroughly after each application and avoid touching your eyes or mouth. Cover treated skin with a loose dressing only if your doctor says it’s safe.

Don’t skip follow‑up appointments. Blood work, imaging scans, or skin checks let doctors adjust the dose before side effects get out of hand.

When to Seek Help

Any sudden increase in pain, unexplained bruising, or persistent vomiting deserves a call to your clinic. Even though fluorouracil can feel harsh, early intervention prevents complications and keeps you on track with treatment goals.

Remember, fluorouracil is a powerful tool that works best when you partner closely with your doctor, follow the dosing plan, and report anything unusual right away.