Fluracil

Indications

Fluorouracil (5-FU) is an anticancer medicine. As an injection it is used, often with other medicines, to treat cancers of the bowel (colon and rectum), breast, stomach, food pipe (oesophagus), pancreas, and head and neck. A cream form is used separately for some skin conditions.

How It Works

Fluorouracil is an antimetabolite: it looks like a natural building block of DNA. Cancer cells take it up, and it blocks an enzyme (thymidylate synthase) they need to make new DNA, so they cannot grow and divide.

Dosage and Administration

Given only as prescribed by a cancer specialist. The dose is worked out from body size, the type of cancer and the treatment plan, and is given in cycles. It is given into a vein, as an injection or a slow drip (sometimes over several days using a pump), by a doctor or nurse in hospital or a chemotherapy unit. Blood tests are done before each cycle.

Interactions

• Brivudine and Sorivudine (antiviral medicines) can cause dangerous, sometimes fatal, fluorouracil toxicity; they must not be used together or within 4 weeks of each other.
• Folinic acid (Leucovorin) increases its effect; this is often used on purpose in treatment plans.
• Warfarin: the risk of bleeding can rise, so blood clotting tests are needed.
• Phenytoin levels can rise.
• Live vaccines should not be given during treatment.

Contraindications

Known complete lack of the enzyme DPD (dihydropyrimidine dehydrogenase); severe bone marrow suppression; serious active infection; very poor general health; recent use of Brivudine or Sorivudine; pregnancy and breastfeeding; allergy to fluorouracil.

Side Effects

Common: nausea, vomiting, diarrhoea, mouth sores, loss of appetite, tiredness, hair thinning, low blood counts, darkening of skin or nails, sensitivity to sunlight, and soreness, redness or peeling of the palms and soles (hand-foot syndrome). Get urgent medical help if you have a temperature of 38°C or higher or shivering, severe or frequent diarrhoea, mouth sores that stop you eating or drinking, unusual bleeding or bruising, chest pain or a racing heartbeat, or sudden confusion or unsteadiness.

Pregnancy and Lactation

Fluorouracil can harm an unborn baby. Do not use it in pregnancy. Both men and women should use reliable contraception during treatment and for some months after, as the doctor advises. Do not breastfeed during treatment.

Precautions and Warnings

Some people have low DPD enzyme levels and can have severe reactions; a test may be done before starting. Tell the doctor about heart disease, liver or kidney problems, and all other medicines you take. Avoid strong sun and use sunscreen. Avoid people with infections where possible. Drink plenty of fluids if you have diarrhoea.

Overdose

Overdose causes severe nausea, vomiting, diarrhoea, mouth ulcers, bleeding and very low blood counts. It is managed in hospital, where a specific antidote may be given if available.

Therapeutic Class

Anticancer medicine (antimetabolite, pyrimidine analogue).

Storage

Kept by the hospital or pharmacy below 30°C (or as the pack says), protected from light. Do not refrigerate or freeze. Keep out of the reach of children.