What is fulvestrant?

Fulvestrant (Faslodex®) is a hormonal therapy drug used to treat breast cancer that has spread. It can be given alone or with other types of treatment. It is best to read this information with our general information about hormonal therapies and advanced breast cancer. It is sometimes given to treat breast cancer in men.

Fulvestrant is usually given if other hormonal therapies have stopped controlling the cancer.

Your cancer doctor or nurse will explain how long you should take fulvestrant for. You usually have it for as long as it is effective in controlling the cancer.

Your doctor will talk to you about this treatment and its possible side effects before you agree (consent) to have treatment.

How fulvestrant works

Hormones are chemicals that our bodies make. Hormones act as messengers and help control how cells and organs work. Hormonal therapies are drugs that change the way hormones are made or how they work in the body.

Many breast cancers need the hormone oestrogen to grow. This is called oestrogen-receptor positive (ER positive) breast cancer. These cancers have receptors (proteins) on the breast cancer cells. The receptors let hormones, such as oestrogen, attach to the cell.

Fulvestrant blocks the receptors and stops oestrogen reaching the cancer cells. This slows down or stops the cancer cells from growing. Fulvestrant also reduces the number of receptors on the breast cancer cells.

When fulvestrant is given

Fulvestrant is used to treat breast cancer that has spread. It is given to treat breast cancer in women who have been through the menopause.

Sometimes it is given to treat breast cancer in men. It is usually given if other hormonal therapies have stopped controlling the cancer.

Your cancer doctor or nurse will explain how long you should take fulvestrant for. You usually have it for as long as it is effective in controlling the cancer.

How is fulvestrant given?

Fulvestrant is given as an injection into a muscle (intramuscular).

You are given fulvestrant as 2 injections, one in each buttock. The injections are given one after the other. Each one takes 1 to 2 minutes.

The first 3 doses are given 2 weeks apart, after that you have the injections once a month. You can have the injections at the hospital or they can be given at your GP surgery by your GP or practice nurse. If you are not able to visit the surgery, a district nurse may give you the injections at home.

If you sometimes delay the injections by a day or two it will not make much difference. But it is important to make sure you have your injections every month as prescribed.

About side effects

We explain the most common side effects of this treatment here. We also include some less common side effects.

You may get some of the side effects we mention, but you are unlikely to get all of them. If you are also having treatment with other cancer drugs, you may have some side effects that we have not listed here. Always tell your doctor, nurse or pharmacist about any side effects you have.

Your doctor can give you drugs to help control some side effects. It is important to take them exactly as your nurse or pharmacist explains. This means they will be more likely to work for you. Your nurse will give you advice about managing your side effects. After your treatment is over, most side effects start to improve.

Serious and life-threatening side effects

Some cancer treatments can cause severe side effects. Rarely, these may be life-threatening. Your cancer doctor or nurse can explain the risk of these side effects to you.

Contact the hospital

Your nurse will give you telephone numbers for the hospital. If you feel unwell or need advice, you can call them at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.

More information

We cannot list every side effect for this treatment. There are some rare side effects that are not listed. You can visit the electronic Medicines Compendium (eMC) for more detailed information.

Side effects while given

Allergic reaction

Some people have an allergic reaction while having this treatment. Signs of a reaction can include:

  • feeling hot or flushed
  • a skin rash
  • itching
  • shivering
  • feeling dizzy
  • a headache
  • feeling breathless.

If you feel unwell or have any of these signs, tell a doctor or nurse straight away. Do not take any more of this treatment until you have spoken to them.

Injection site

You may have some pain, swelling, redness, or a darker colour around the area that was injected. Let your doctor know if this happens. Painkillers may help.

Hot flushes and sweats

These are common. During a flush, your neck and face may feel warm and look red. Flushes can last for a few seconds or for up to 10 minutes. You may have sweats then feel cold and clammy. Some people feel anxious or irritable during a hot flush.

There are things you can do to try to reduce flushes:

  • Wear clothes made from natural fabrics, such as cotton.
  • Dress in layers of clothes that you can remove as needed.
  • Use cotton sheets and have layers of bedding.
  • Keep the room temperature cool or use a fan.
  • Have cold drinks rather than hot ones. Try to avoid drinks with caffeine in them.

You may have fewer hot flushes and sweats as your body adjusts to hormonal treatment. Or your doctor can prescribe drugs to help. Some people continue to have flushes and sweats but they usually stop a few months after treatment finishes.

Women coping with hot flushes can read more in our information about managing menopausal symptoms. Men coping with hot flushes can read more in our information about managing hormonal symptoms.

Common side effects

Feeling sick

You may feel sick in the first few days after this treatment. Your doctor will give you anti-sickness drugs to help prevent or control sickness. Take the drugs exactly as your nurse or pharmacist tells you. It is easier to prevent sickness than to treat it after it has started.

If you feel sick, take small sips of fluids and eat small amounts often. If you continue to feel sick, or if you vomit more than once in 24-hours, contact the hospital as soon as possible. They will give you advice and may change the anti-sickness drug to one that works better for you.

Diarrhoea

This treatment may cause diarrhoea. Diarrhoea means passing more stools (poo) than is usual for you, or having watery or loose stools. If you have a stoma, it will be more active than usual.

If you have diarrhoea:

  • try to drink at least 2 litres (3½ pints) of fluids each day
  • avoid alcohol, caffeine, milk products, high-fat foods and high-fibre foods
  • contact the hospital for advice.

Feeling tired

Feeling tired is a common side effect. It is often worse towards the end of treatment and for some weeks after it has finished. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can give you more energy. If you feel sleepy, do not drive or operate machinery.

Headaches

This treatment may cause headaches. If this happens, tell your doctor or nurse. They can give you painkillers.

Muscle or joint pain

You may get pain in your muscles or joints for a few days after treatment. If this happens, tell your doctor so they can give you painkillers. Tell them if the pain does not get better. Having warm baths and taking regular rests may help.

Effects on the liver

Treatment may affect how your liver works. This is usually mild. You will have blood tests to check how well your liver is working.

Skin changes

This treatment may affect your skin. Your doctor or nurse can tell you what to expect. If your skin feels dry, try using an unperfumed moisturising cream every day. It can cause a rash, which may be itchy.

Always tell your doctor or nurse about any skin changes. They can give you advice and may prescribe creams or medicines to help. Any changes to your skin are usually temporary and improve when treatment finishes.

Urine infection

Fulvestrant can make you more likely to get a urine infection. Let your doctor know if you have pain or discomfort when you pass urine, if you need to go more often or if your urine is cloudy or smelly. Your doctor may prescribe antibiotics.

Less common side effects

Blood clots (thrombosis)

Fulvestrant slightly increases the chances of a blood clot. A clot can cause symptoms such as:

  • pain
  • redness and swelling in a leg or arm
  • breathlessness
  • chest pain.

Contact your doctor straight away if you have any of these symptoms. A blood clot is serious but your doctor can treat it with drugs that thin the blood. Your doctor or nurse can give you more information.

Vaginal bleeding or discharge

Some women may have vaginal bleeding. If this happens it is usually in the first few weeks of treatment. Or it may happen when you change from another hormonal therapy to fulvestrant. If it continues for more than a few days tell your doctor or nurse.

Another uncommon side effect is a white vaginal discharge or sometimes vaginal thrush. Tell your doctor if you have this.

Bruising and bleeding

Fulvestrant can reduce the number of platelets in your blood. Platelets are cells that help the blood to clot. Tell your doctor if you have any bruising or bleeding you cannot explain. This includes nosebleeds, bleeding gums, blood spots or rashes on the skin.

Always let your doctor or nurse know about any side effects you have, as there are usually ways in which they can be controlled or improved.

Other information

Fertility

Some cancer drugs can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.

Contraception

Your doctor will advise you not to get pregnant or make someone pregnant while having this treatment. The drugs may harm a developing baby. It is important to use contraception during your treatment and for a while after treatment finishes. Your doctor, nurse or pharmacist can tell you more about this.

Breastfeeding

Women are advised not to breastfeed while having this treatment. This is because the drugs could be passed to the baby through breast milk.

Medical and dental treatment

If you need medical treatment for any reason other than cancer, always tell the doctors and nurses that you are having cancer treatment. Give them the contact details for your cancer doctor so they can ask for advice.

If you think you need dental treatment, talk to your cancer doctor or nurse. Always tell your dentist you are having cancer treatment.

Alcohol

This treatment contains alcohol. If this is a problem for you, tell your doctor, nurse or pharmacist. Your blood alcohol level may be above the legal limit after you have the treatment. It is best not to drive or operate machinery for a few hours after having this treatment, even if you feel okay.

How we can help

How to print a PDF from this website
Instructions on how you can make a PDF version of this page using the print function on your browser.
Clinical Information Nurse Specialists
Our Cancer Information Nurse Specialists are dedicated cancer nurses available to talk to on our Macmillan Cancer Support Line. 
0808 808 00 00
7 days a week, 8am - 8pm
Email us
Get in touch via this form
Chat online
7 days a week, 8am - 8pm
Online Community
An anonymous network of people affected by cancer which is free to join. Share experiences, ask questions and talk to people who understand.
Help in your area
What's going on near you? Find out about support groups, where to get information and how to get involved with Macmillan where you live.