Understanding Fluorouracil (5FU)
Fluorouracil (pronounced floor-oh-YOOR-uh-sil), commonly called 5FU, is a chemotherapy drug classified as an antimetabolite. It’s used to treat various cancers, including:
- Colorectal cancer
- Breast cancer
- Stomach cancer
- Pancreatic cancer
- Skin cancer (as a topical cream)
How Does 5FU Work?
5FU mimics natural molecules in the body but with a key difference—it blocks DNA production in rapidly dividing cancer cells. Without DNA, cancer cells can’t grow or multiply, leading to tumor shrinkage.
How is 5FU Given?
1. Intravenous (IV) Infusion
- Short-term: Through a cannula (arm vein, replaced each session).
- Long-term: Via a central line, PICC line, or portacath (for multiple cycles).
- Continuous infusion: Some patients wear a portable pump for days at a time.
2. Topical Cream (For Skin Cancer)
- Applied directly to actinic keratosis or superficial skin cancers.
- Causes local irritation but avoids systemic side effects.
Treatment Schedule & Cycles
5FU is given in cycles, with rest periods for recovery. The exact schedule depends on cancer type:
- Weekly infusions
- Every 2-4 weeks (combined with other chemo drugs like leucovorin or oxaliplatin)
- Continuous pump infusion (over 46-48 hours)
Before Starting: DPD Enzyme Test
A blood test checks for DPD deficiency (low levels of dihydropyrimidine dehydrogenase).
- DPD deficiency increases severe side effect risks.
- If deficient, your doctor may lower the dose or choose alternative treatment.
Common Side Effects (Occur in >10% of Patients)
| Side Effect | Management Tips |
|---|---|
| Infection risk (low white blood cells) | Watch for fever (≥37.5°C), chills, cough. Seek urgent medical help. |
| Fatigue & weakness | Rest when needed; light exercise may help. |
| Nausea & vomiting | Take anti-sickness meds as prescribed. Eat small, frequent meals. |
| Diarrhea | Stay hydrated; use anti-diarrheal meds if prescribed. |
| Mouth sores | Use a soft toothbrush, avoid acidic/spicy foods, rinse with saltwater. |
| Hand-foot syndrome | Moisturize skin; avoid hot water & friction. |
| Hair thinning/loss | Scalp cooling may help. Hair regrows post-treatment. |
Less Common but Serious Side Effects
⚠ Heart problems (irregular heartbeat, chest pain) → Seek emergency care.
⚠ Severe allergic reaction (rash, swelling, breathing difficulty) → Call 911.
⚠ Lung issues (shortness of breath, cough) → Report immediately.
Important Precautions
Before Treatment
✔ Blood tests (check liver, kidney, blood cell counts).
✔ Heart tests (ECG) if high-risk for cardiac issues.
During Treatment
- Avoid grapefruit (interferes with drug metabolism).
- Use sunscreen (skin becomes more sun-sensitive).
- Stay hydrated (helps flush toxins).
Pregnancy & Fertility
- Contraception required (for both men & women).
- Women: Avoid pregnancy 6+ months post-treatment.
- Men: Avoid fathering a child 3+ months post-treatment.
- Fertility preservation options (sperm/egg freezing) should be discussed before starting chemo.
Vaccinations
🚫 No live vaccines (MMR, BCG, yellow fever) during & 12 months after treatment.
✅ Safe vaccines: Flu shot, COVID-19 vaccine (may be less effective).
When to Call Your Doctor
🆘 Fever ≥37.5°C or chills (sign of infection).
🆘 Severe diarrhea (≥6 loose stools/day).
🆘 Chest pain, irregular heartbeat.
🆘 Unusual bleeding/bruising.
Long-Term Monitoring
- Regular blood tests (check for anemia, liver/kidney function).
- Heart follow-ups (if high-dose or prolonged use).
Additional Resources
- Patient Leaflet: UK eMC Website
- Side Effect Reporting: MHRA Yellow Card Scheme
Final Thoughts of Fluorouracil 5 FU
5FU is a powerful chemotherapy drug with manageable side effects when monitored closely. Always follow your oncology team’s guidance for the best outcomes.
Have questions about 5FU treatment? Ask in the comments below!
Disclaimer: This guide is for educational purposes only. Always consult your healthcare team for personalized medical advice.