Fluorouracil

• What fluorouracil is
• How you have treatment
• Common side effects
• Occasional side effects
• Rare side effects
• Important points to remember
• Immunisations and chemotherapy

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 called Efudix 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.

Some other medicines can change how well fluorouracil works, making the fluorouracil either not work so well. Or the fluorouracil can change how some other medicines work. You should not take some antiviral drugs at the same time as fluorouracil and if you take phenytoin your doctor should check the levels of phenytoin in your blood as the fluorouracil can interfere with how your body absorbs the drug.

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.

With this drug, many people have a temporary drop in the number of blood cells made by the bone marrow, leading to the following side effects

• Increased risk of getting an infection from a drop in white blood cells - it is harder to fight infections and you can become very ill. You may have headaches, aching muscles, a cough, sore throat, pain passing urine or feel cold and shivery. 
• Tiredness and breathlessness due to a drop in red blood cells (anaemia) - you may need a blood transfusion
• Bruising more easily due to a drop in platelets - you may have nosebleeds, bleeding gums after brushing your teeth, or lots of tiny red spots or bruises on your arms or legs (known as petechia).

These effects on your bone marrow can begin about 7 days after each treatment and usually go back to normal after about 21 to 28 days. Some of these side effects can be life threatening, particularly infections.  You should contact your doctor if you have any of these side effects.  Your doctor will check your blood counts regularly to see how well your bone marrow is working

Other common side effects include

• 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.
• 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.

 

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
• Continuous infusion of fluorouracil can occasionally cause soreness and redness of the palms of the hands and soles of the feet (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.

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.

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.

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.