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Trastuzumab (Herceptin)

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This page tells you about the possible side effects of the biological therapy trastuzumab (Herceptin). There is information about


What trastuzumab is

Trastuzumab is a monoclonal antibody – a type of targeted treatment. It has the brand name Herceptin. It is used for cancers that have large amounts of a protein called HER2 (human epidermal growth factor receptor 2). Some breast cancers and stomach cancers have large amounts of HER2 and they are called HER2 positive cancers. HER2 makes the cancer cells grow and divide. When Herceptin attaches to HER2 it can make the cells stop growing and die. 

Trastuzumab for HER2 breast cancer that has spread

As a first treatment for breast cancer that has spread you may have trastuzumab with the chemotherapy drugs paclitaxel (Taxol) or docetaxel (Taxotere) or hormone therapies called aromatase inhibitors.

Trastuzumab may be used as a treatment on its own for people who have had at least two types of chemotherapy for breast cancer that has spread and where hormone therapy has not worked. 

Trastuzumab for HER2 early breast cancer

Trastuzumab may be used alongside chemotherapy used before or after surgery and radiotherapy.

Trastuzumab for stomach cancer that has spread

Trastuzumab may be used as a first treatment for a type of stomach cancer called adenocarcinoma of the stomach. You also have chemotherapy with the drug capecitabine (Xeloda) or a combination of fluorouracil and cisplatin

Trastuzumab is also used for cancer of the area where where the food pipe meets the stomach (gastro oesophageal cancer).


How you have trastuzumab

You have trastuzumab into your bloodstream by drip (infusion). You may have it through a thin, short tube (a cannula) put into a vein in your arm each time you have treatment. Or you may have it through a central line, a portacath or a PICC line. These are long, plastic tubes that give the drug directly into a large vein in your chest. You have the tube put in just before your course of treatment starts and it stays in place as long as you need it. Having trastuzumab into a vein takes about 30 to 90 minutes each time.

Trastuzumab is also available as an injection under the skin (a sub cutaneous injection) for women with breast cancer. The injection takes from 2 to 5 minutes.

For breast cancer, you usually have the treatment once a week or 3 weekly. For stomach cancer you have it every 3 weeks. 

For early breast cancer you have the treatment for a year. For breast cancer or stomach cancer that has spread you have it for as long as it is controlling the cancer.

The side effects associated with trastuzumab are listed below. You can use the links (underlined) to find out more about each side effect or look in the cancer drug side effects section. If you are having other drugs in combination with trastuzumab you may also have side effects related to those drugs. 


Common side effects

More than 10 in every 100 people have one or more of these 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 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)
  • A reaction while the drug is given causing chills, fever, swelling of the face and lips, and possibly an itchy rash, feeling sick, breathlessness, wheezing, a headache, flushes, dizziness and faintness – this happens to about half of patients with the first treatment but less often with further treatments. More rarely, it is possible to have a more severe reaction to your first infusion, but your nurse will be watching for this
  • Soreness at the injection area may occur if you have trastuzumab as an injection under the skin
  • Tiredness and weakness (fatigue) during and after treatment – most people find their energy levels are back to normal from 6 months to a year after their treatment finishes
  • Skin rashes
  • Diarrhoea – this affects about 1 in 3 people. It is usually mild but do tell your doctor or nurse as you can be given medicines to stop it
  • Numbness or tingling in the fingers and toes – you may have trouble with fiddly tasks such as doing up buttons. This can start a few days or weeks after treatment and usually goes away within a few months of the treatment finishing
  • Heart problems such as an irregular heartbeat or palpitations – this should get better once treatment is stopped. You will have heart tests before you start treatment and regularly throughout your treatment. You cannot have this drug for early breast cancer if you already have particular heart conditions such as congestive heart failure or angina that needs treatment
  • Taste changes
  • Loss of appetite
  • Weight loss
  • Pain – this may affect the abdomen (tummy), chest, joints or muscles
  • A sore mouth
  • Some people develop soreness, redness and peeling on the palms of the hands and soles of the feet (palmar – plantar syndrome) which may cause tingling, numbness, pain and dryness
  • Low or high blood pressure
  • Sore, red eyes (conjunctivitis)
  • Watery eyes
  • A runny nose 
  • Shaking
  • Hot flushes
  • Dizziness
  • Difficulty sleeping
  • Swollen hands and feet

Occasional side effects

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

  • Long term weakening of the heart muscle leading to chest pain, breathlessness, a cough, swelling in the arms or legs and heart fluttering
  • Indigestion (heartburn)
  • Constipation – drink plenty of fluids. Your doctor or specialist nurse can give you laxatives so let them know if you are constipated for more than 3 days
  • Shingles – pain and a rash in an area of skin. Let your doctor or nurse know if you have this
  • Kidney changes – you will have regular blood tests to check how well your kidneys are working
  • Changes in your nails
  • Hair thinning
  • Sleep problems
  • Itching – let your doctor or nurse know as they may be able to prescribe medicines to help
  • A dry mouth
  • Dry skin
  • Sweating
  • Anxiety or depression
  • Breathlessness from a chest infection or fluid build up around the lungs – let your doctor or nurse know straight away if you suddenly become breathless or develop a cough
  • A sore throat due to infection – let your doctor or nurse know straight away if your suddenly becomes sore

Rare side effects

Fewer than 1 in 100 people have these.

  • Long term lung changes leading to difficulty breathing and a cough
  • Liver problems – you may have regular blood tests to check this
  • Women may stop having periods (amenorrhoea) – this may only be temporary
  • Loss of fertility –– you may not be able to become pregnant or father a child after treatment with this drug. Talk to your doctor before starting treatment if you think you may want to have a baby in the future. Men may be able to store sperm before starting treatment

Important points to 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

Coping with side effects

Talk to your doctor, pharmacist or nurse about all your side effects so 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. It can take up to 7 months for trastuzumab (Herceptin) to be removed from the body so tell your doctor that you have had Herceptin before starting any new medicines during this time. 

Pregnancy and contraception

Trastuzumab can have harmful effects on a baby developing in the womb. You should not become pregnant while taking trastuzumab or for 7 months afterwards. Talk about contraception to your doctor or nurse before having the treatment if there is any chance that you could become pregnant. 


Breastfeeding is not advisable during this treatment and for 7 months afterwards because the drug may come through in the breast milk.



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 trastuzumab

This page does not 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

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at

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Updated: 4 August 2014