Fluorouracil

Fluorouracil is also known as FU or 5FU and is one of the most commonly used drugs to treat cancer. It is used to treat many types of cancer including, breast, head and neck, anal, stomach, colon and some skin cancers.

Fluorouracil is part of a group of chemotherapy drugs known as the anti-metabolites. Anti-metabolites are similar to normal body molecules but they are slightly different in structure. These differences mean that anti-metabolites stop cells working properly. Anti-metabolites often stop cells making and repairing DNA. Cancer cells need to make and repair DNA in order to grow and multiply. Anti-metabolites also stop normal cells working properly. This is why you get side effects.

You can have fluorouracil as an injection or infusion into a vein (intravenously). It can also be used as an ointment for skin cancer.

You usually have intravenous fluorouracil as a course of several cycles of treatment. The exact treatment plan depends on which cancer you are being treated for. To find out more about the way chemotherapy treatment is planned click on planning chemotherapy.

The side effects associated with intravenous fluorouracil are listed below. You can use the links (underlined) to find out more about each side effect. Where there is no link, please see our chemotherapy side effects section or click on 'search' at the top of the page.


Common side effects

Many people have one or more of the following side effects


Fatigue - for many people this is the most troublesome side effect of all. Tiredness often carries on after treatment has ended. Most people find their energy levels are back to normal from 6 months to a year after their treatment finishes.
Feeling or being sick (this is usually mild)
Mouth sores and ulcers
Diarrhoea - you should drink plenty of fluids. If it becomes severe or persistent you could get dehydrated so tell your doctor or nurse.
Temporary effect on the bone marrow. The bone marrow makes blood cells and a drop in its function can cause

- An increased risk of getting infections. This is due to a temporary drop in the number of white blood cells produced by the bone marrow. Having a low white blood count means that you are less able to fight infections and can become very ill. You may have headaches, aching muscles, a cough, sore throat, pain passing urine or feel cold and shivery. Infections can sometimes be life threatening. You should contact your hospital urgently if you think you have an infection.

- Tiredness and breathlessness. This is due to a drop in the number of red blood cells made by your bone marrow which is called anaemia. You may need a blood transfusion to treat anaemia.

- Getting bruises more easily. This is due to a drop in the number of platelets produced by your bone marrow. You may have nosebleeds or notice your gums bleed when you brush your teeth. You may have lots of tiny red spots or bruises on your arms or legs. Contact your hospital if you have any of these effects.

This drug may have a harmful effect on a baby developing in the womb. It is not advisable to become pregnant or father a child while on chemotherapy. You should talk to your doctor about contraception before having the treatment.
Occasional side effects

Some people have the following side effects


Hair thinning
Brittle, chipped and ridged nails
Sensitivity of the skin to sunlight - you should not use sunbeds or sit in the sun if having fluorouracil. Cover up or use a sun block.
Rashes which may be itchy
Watery eyes from increased production of tears
Gritty eyes and blurred vision
Loss of appetite
Brown marking on the skin following the line of the vein where fluorouracil has been injected
With continous infusion of fluorouracil an occasional side effect is soreness and redness of the palms of the hands and soles of the (sometimes called hand and foot syndrome or palmar-plantar syndrome). This causes tingling, numbness, pain, dryness, and a rash. Tell your doctor if this happens - you can be given vitamin B6 (pyridoxine) to help control this effect. It can help to keep your hands and feet cool, avoid very hot water, avoid tight fitting gloves or socks and keep your skin well moisturised.
Rare side effects

A very small number of people have these side effects


Total hair loss
Darkened skin
Angina or heart attack
Confusion or unsteadiness
Loss of fertility - you may not be able to get pregnant or father a child after treatment with this drug. It is important to talk to your doctor about your fertility before starting treatment. Women may stop having periods (amenorrhoea). This may only be temporary.
Remember



The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment, or more side effects may develop as the course goes on. This depends on

• How many times you've had the drug before
• Your general health
• The amount of the drug you have (the dose)
• Other drugs you are having

Some side effects are inconvenient or upsetting but not damaging to your health.

Some side effects are serious medical conditions and need treating. Where we have urged you to contact your doctor, this is because

• Your side effect may need treating
• Your drug dose may need reducing to try to prevent the side effect

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and other over the counter remedies - some drugs can react together.

Talk to your doctor, pharmacist or nurse about all your side effects so that they can help you manage them. Your chemotherapy nurse, clinic or ward nurse will have given you a contact number. You can ring if you have any questions or problems. They can give you advice or reassure you. If in doubt, call them.


Immunisations

You should not have immunisations with live vaccines while you are having chemotherapy or for 6 months afterwards. In the UK, these include rubella, mumps, measles (usually given together as MMR), BCG and yellow fever. You can have other vaccines, but they may not give you as much protection as usual until your immune system has fully recovered from your chemotherapy.

It is perfectly safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with oral vaccines, but no one in the UK is given an oral vaccine now. So there is no problem in being with any baby or child who has recently had any vaccination in the UK. If you live abroad, you might need to make sure that you aren't in contact with anyone who has had oral polio or oral typhoid vaccination recently.

Cancer Research UK
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