Fulvestrant (Faslodex) | Cancer Research UK
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What fulvestrant is

Fulvestrant (pronounced full-vest-rant) is a type of hormone treatment. It is also called Faslodex. It is a treatment for post menopausal women with advanced breast cancer.


How fulvestrant works

Many breast cancers are stimulated to grow by the female sex hormones oestrogen and progesterone. These breast cancers are called hormone sensitive or hormone receptor positive. Drugs that block the effects of these hormones can slow or stop the growth of the breast cancer cells. Fulvestrant stops oestrogen getting to the cancer cells by blocking oestrogen receptors and reducing the number of receptors the cancer cells have.


How you have fulvestrant

You have fulvestrant as two injections – one into each buttock. You can have it at your GP surgery. Your doctor or practice nurse gives you the injections. They each take 1 to 2 minutes. You have the injections two weekly for the first 3 doses and then monthly.


Tests during treatment

You have blood tests before starting treatment and regularly during your treatment. The tests check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.


About side effects

We've listed the side effects associated with fulvestrant. You can use the links to find out more about each side effect. Where there is no link, please go to our cancer drug side effects section or use the search box at the top of the page.

You may have a few side effects. They 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)

The side effects may be different if you are having fulvestrant with other drugs.

Tell your doctor or nurse straight away if any of the side effects get severe.


Common side effects

More than 10 in every 100 women have one or more of these.


Occasional side effects

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

  • Headaches
  • Being sick – let your doctor or nurse know if you have this as anti sickness medicines can help
  • Diarrhoea
  • Loss of appetite
  • A skin rash
  • An increased risk of blood clots – let your doctor or nurse know straight away if you have a red, hot, swollen area  on your leg or if you suddenly develop a cough, breathlessness or chest pain
  • Urine infections
  • Back pain – tell your doctor or nurse if you have this
  • A cough and breathlessness
  • Constipation
  • Hot flushes and sweats
  • Joint and bone pain
  • An allergic reaction soon after having the injections – let your nurse or doctor know straight away if you have a sudden skin rash, itching, breathlessness or swelling of the lips, face or throat


Rare side effects

Fewer than 1 in 100 women have these.

  • Vaginal bleeding, a white discharge, or rarely vaginal infection – let your doctor or nurse know if you have vaginal itching or discomfort
  • Weakening of the bones due to loss of bone density – the bones are more likely to break. You will have a DEXA scan to check your bone density before you start treatment or shortly afterwards
  • Bruising more easily due to a drop in platelets – you may have nosebleeds, or bleeding gums after brushing your teeth. Or you may have lots of tiny red spots or bruises on your arms or legs (known as petechiae)
  • Liver failure – let your doctor or nurse know if you feel unwell or if you have yellowing of the skin or whites of the eyes

Important points to remember

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.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant while you are having treatment and for a few 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.

Alcohol and fulvestrant

Fulvestrant contains alcohol (equal to a small amount of beer or wine) and may harm people who have alcohol problems.


Related information

On this website you can read about

Hormone treatment

Breast cancer

Hormone symptoms


More information about fulvestrant

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 www.medicines.org.uk.

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 www.mhra.gov.uk.

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Updated: 1 July 2015