Anastrozole

Anastrozole is a hormonal therapy drug.  It is usually only used after you have been through menopause.

It is used to:

Anastrozole is also sometimes used to:

  • reduce the risk of breast cancer developing if your family history or a genetic test shows you have a higher risk of breast cancer.  

It is best to read this information with our general information about hormonal therapies and the type of cancer you have. 

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

Anastrozole and breast cancer prevention

Updated November 2023

You may have read in the news recently about anastrozole being offered in England to prevent breast cancer.

Anastrozole can be used after menopause to reduce the risk of breast cancer developing if your family history or a genetic test shows you have a higher risk of breast cancer.

For more information about this story, please visit the NHS England website.

 

How anastrozole works

Hormones are chemicals that our bodies make. They 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 rely on the hormone oestrogen (or estrogen) to grow. This is called oestrogen receptor-positive (ER positive) breast cancer.

Anastrozole blocks an enzyme (a type of protein) that helps produce oestrogen in the fatty tissues of the body. This reduces the amount of oestrogen in the body.

Taking anastrozole tablets

During a course of treatment, you usually see a:

  • cancer doctor
  • specialist nurse
  • specialist pharmacist. 

This is who we mean when we mention doctor, nurse or pharmacist in this information

Anastrozole comes as tablets you can take at home. You may have it with other drugs. You take it once a day, with or without food. Try to take it at the same time each day. Swallow the tablet whole with a glass of water.

If you forget to take your tablet, take your next dose as usual. Do not take a double dose.

Anastrozole is a long-term treatment. You may need to take it for several years. Your nurse, doctor or pharmacist will talk to you about your treatment plan. Always take the tablets exactly as explained. This is important to make sure they work as well as possible for you.

Other things to remember about your tablets:

  • Keep them in the original package and at room temperature, away from moisture, heat and direct sunlight.
  • Keep them safe, somewhere children cannot see or reach them.
  • Get a new prescription before you run out of tablets, and make sure you have plenty for holidays.
  • If your treatment is stopped, return any unused tablets to the pharmacist.

Your doctor, nurse or pharmacist may also give you other medicines to take home. Take all your medicines exactly as they have been explained to you. Do not stop taking any of your medicines unless they tell you to.

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. You may have some rarer side effects that we have not listed here.

If you are having other cancer treatments, you may have some side effects that we have not listed here. 

You will see a doctor, nurse or pharmacist regularly while you are having this treatment. Always tell them about any side effects you have. They can give you drugs to help control most side effects. They can also offer advice to help you cope. 

Most side effects can be managed. But sometimes side effects are harder to control. It is important not to stop taking hormonal therapy without telling your doctor. If side effects cannot be managed, your doctor may suggest you take a different type of hormonal therapy.

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.

Common side effects

Hot flushes and sweats

Hot flushes are a common side effect of this treatment. During a flush, your neck and face may feel warm and look red. Flushes may last from a few seconds up to 10 minutes. You may have sweats and 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.
  • Wear layers of clothes that you can remove if you feel hot.
  • Use cotton bed sheets and have layers of bedding that you can remove if you feel hot.
  • Keep room temperatures 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. Flushes and sweats usually stop a few months after treatment finishes, but some people continue to have them.

You can read more about coping with hot flushes in our information about managing menopausal symptoms.

Muscle or joint pain

You may get pain in your muscles or joints. If this happens, tell your doctor so they can give you painkillers. Being physically active may help with the pain and keep your joints flexible. Keeping to a healthy weight may help too. Tell your doctor or nurse if the pain does not get better.

Feeling sick

Any sickness is usually mild. Tell your doctor, nurse or pharmacist if this happens. It may help to take your anastrozole tablets with food or at night. 

Headaches

This treatment may cause headaches. If you have headaches, tell your doctor. They may give you painkillers to help.

Skin changes

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

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

Bone thinning (osteoporosis)

If you take this treatment for several months or more, you may get bone thinning. This is called osteoporosis. This can increase your risk of a broken bone (fracture). You may have bone density scans to check your bone health before and during treatment.

Doing regular exercise, such as walking, can improve your bone health. Eating a healthy diet can help too. Your doctor may prescribe drugs called bisphosphonates to help protect your bones. They may also advise you to take calcium and vitamin D supplements.

Low mood or depression

If your mood is low, or you think you may be depressed, talk to your doctor, nurse or GP. It is common to have different feelings when you are diagnosed with cancer. Or you may be dealing with hormonal changes.

Your doctor or nurse can refer you for counselling or talk to you about medication that might help. We have more information about getting help with depression.

Less common side effects

Vaginal bleeding or dryness

This treatment can cause vaginal changes. You may have bleeding when you start this treatment, or if you change to anastrozole from another treatment. If bleeding continues for more than a few days, tell your doctor or nurse.

Talk to your doctor, nurse or pharmacist about treatments to help with vaginal dryness. They can give advice and may be able to prescribe something to help. You can buy non-hormonal creams, gels or lubricants from a chemist. We have more information about cancer and sex

Loss of appetite

This treatment can affect your appetite. If you do not feel like eating 3 big meals a day, try to eat small, frequent meals or snacks instead.

Changes to your taste

You may get a bitter or metal taste in your mouth. Sucking sugar-free sweets may help with this. Some foods may taste different or have no taste. Try different foods to find out what tastes best to you. Taste changes usually get better after treatment finishes. Your nurse can give you more advice.

Diarrhoea

This is usually mild. If it does not get better, your doctor, nurse or pharmacist can prescribe drugs to control it. If you have diarrhoea, make sure you drink at least 2 litres (3½ pints) of fluids every day.

Hair thinning

Your hair may become thinner when you are taking this treatment. This is usually mild. Ask your nurse for advice if you are worried about this.

Effects on the liver

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

Raised cholesterol level

This treatment can raise the level of cholesterol (a fatty substance) in the blood. You may have a blood test to check the level of cholesterol. Your doctor may give you medicines to control your cholesterol levels.

Pain, numbness or tingling in hand and fingers

Some people may get pain, numbness or tingling in the hands and fingers. These symptoms may be caused by carpal tunnel syndrome, which is caused by pressure on a nerve in the wrist. If you have these symptoms, tell your doctor, nurse or pharmacist.

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.

Other information

Blood clot risk

Cancer and some cancer treatments can increase the risk of a blood clot. Contact the hospital straight away on the 24-hour number if you have any of these symptoms during or after treatment:

  • throbbing pain or swelling in a leg or arm
  • reddening of the skin in the area – if you have black or brown skin, this can be harder to notice, but the skin might become darker
  • suddenly feeling breathless or coughing.

Always call 999 if you have:

  • chest pain
  • difficulty breathing.

A blood clot is serious, but it can be treated with drugs called anticoagulants. These thin the blood. Your doctor, nurse or pharmacist can give you more information about preventing and treating blood clots.

Other medicines

Some medicines can affect how this treatment works or be harmful while you are having it. Always tell your cancer doctor, nurse or pharmacist about any drugs you are taking or planning to take, such as: 

Lactose

These tablets contain a type of sugar called lactose. If you have been told by a doctor that you cannot digest some sugars or are lactose intolerant, talk to your doctor before taking this drug.

Breastfeeding

You are advised not to breastfeed while having this treatment, or for some time after treatment finishes. This is because the drugs could be passed to the baby through breast milk.

Your doctor or nurse can give you more information.

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.

Medical and dental treatment

If you need medical treatment for any reason other than cancer, always tell the doctors and nurses 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.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert health professionals and people living with cancer.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 November 2023
|
Next review: 01 November 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

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