Teysuno | Cancer Research UK
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What Teysuno is

Teysuno (prounounced tay-sun-oh) is a chemotherapy drug used to treat advanced stomach cancer. You have it in combination with another chemotherapy drug called cisplatin.

You may also have it as part of trials for other cancers.

Teysuno is made up of 3 drugs

  • Tegafur – the body changes tegafur into a common chemotherapy drug called fluorouracil
  • Gimeracil, which makes tegafur last longer in the body so you need a lower dose
  • Oteracil – this protects normal cells and so reduces the side effects

It is one of a group of chemotherapy drugs known as the anti metabolites. These stop cells making and repairing DNA. Cancer cells need to make and repair DNA in order to grow and multiply.


How you have Teysuno

Teysuno is a capsule. You take the capsules twice a day, morning and evening. Swallow them whole with plenty of water. You should take the capsules either an hour before eating or an hour after eating.  

It is very important that you take capsules according to the instructions your doctor or pharmacist gives you. For example, whether you have a full or empty stomach can affect how much of a drug gets into your bloodstream. So check the pack leaflet and follow the instructions it gives. You should take the right dose, not more or less. And never stop taking a cancer drug without talking to your specialist first.

For advanced stomach cancer you take Teysuno twice a day for 3 weeks and then don’t take it for a week. This is one cycle of treatment. Then your next cycle of treatment starts. You usually continue taking it in this way for as long as it works.  

Teysuno’s side effects are listed below. You can use the links to find out more about each side effect.

For general information, see our cancer drug side effects section.


Common side effects

More than 10 in every 100 people have one or more of these side effects

  • An 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, a sore throat, pain passing urine, or you may feel cold and shivery. If you have a severe infection this can be life threatening. Contact your treatment centre straight away if you have any of these effects or if your temperature goes above 38°C. You will have regular blood tests to check your blood cell levels
  • Tiredness and breathlessness from a drop in red blood cells (anaemia) – you may need a blood transfusion
  • Bruising more easily from 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)
  • Feeling or being sick happens in about 6 out of every 10 people (60%) – this is usually well controlled with anti sickness medicines
  • Tiredness and weakness affects about 4 in 10 people (40%) during and after treatment
  • Diarrhoea happens in about 3 out of 10 people (30%) – drink plenty and tell your doctor or nurse if you are worried about how bad it is, or if it continues for more than 3 days
  • Loss of appetite occurs in about 3 out of 10 people (30%)
  • Constipation – your nurse may give you medicines to help prevent this. Tell them if you are constipated for more than 3 days
  • Numbness or tingling in fingers and toes that can cause difficulty with fiddly things such as doing up buttons. This starts within a few days or weeks and usually goes within a few months of finishing treatment

Occasional side effects

Between 1 and 10 in every 100 people have one or more of these side effects


Rare side effects

Fewer than 1 in 100 people have these side effects

  • Mood changes – you may feel sad and depressed
  • Liver changes that are very mild and unlikely to cause symptoms. These will almost certainly go back to normal when treatment is finished. You will have regular blood tests to check how well your liver is working
  • Chest pain due to damage to heart muscle – this is usually temporary but for a small number of people may be permanent
  • Blood clots – let your nurse or doctor know if you have a sore, painful, red area on your leg or sudden chest pain and breathlessness
  • A stroke or mini stroke – let your nurse or doctor know straight away if you have facial weakness, arm weakness, or speech problems
  • A split in the wall of the bowel (bowel perforation) is very rare but is a serious side effect if it happens. Let your doctor or nurse know straight away if you have sudden, severe tummy (abdominal) pain
  • Loss of interest in sex
  • Breast tenderness
  • Difficulty getting an erection

Important points to remember

You will not get all these side effects and they may be mild. A side effect may get worse through your course of treatment. Or you may have more side effects as the course goes on. This depends on

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

Coping with side effects

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

Other medicines

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

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment with this drug and for 6 months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


Do not breastfeed during this treatment because the drug may come through in the breast milk.


Immunisations and chemotherapy

You should not have immunisations with live vaccines while you are having treatment or for at least 6 months afterwards. In the UK, these include rubella, mumps, measles (usually given together as MMR), BCG, yellow fever and Zostavax (shingles vaccine).

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 treatment. It is safe to have the flu vaccine.

It is safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with vaccines you take by mouth (oral vaccines), but not many people in the UK have these now. So there is usually no problem in being with any baby or child who has recently had any vaccination in the UK. You might need to make sure that you aren't in contact with anyone who has had oral polio, cholera or typhoid vaccination recently, particularly if you live abroad.


More information about Teysuno treatment

We don’t list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at www.medicines.org.uk/emc

If you have a side effect we don’t mention here and you think it may be due to this treatment, you can report it to the Medicines Health and Regulatory Authority (MHRA) at www.mhra.gov.uk

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Updated: 27 October 2014