Exemestane (Aromasin)

Exemestane is a type of hormone therapy drug. It is also known by its brand name Aromasin. You might have it as a treatment for breast cancer after you have had the menopause.

How exemestane 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. Blocking the effects of these hormones can treat breast cancer.

In women who have had their menopause, oestrogen is mainly produced by changing androgens (sex hormones produced by the adrenal glands) into oestrogens. This process is called aromatisation and happens mainly in the fatty tissues, muscle and skin. It needs a particular enzyme called aromatase.

Exemestane blocks the process of aromatisation. So it lowers the amount of oestrogen in the body. In early breast cancer, taking exemestane can help to stop breast cancer coming back. In advanced breast cancer, the cancer cells may grow more slowly or stop growing completely.

How you have exemestane

You have exemestane as tablets. Try to take it at the same time each day, preferably after a meal. Swallow the tablet whole with a drink of water.

Taking your tablets

Speak to your pharmacist if you have problems swallowing the tablets.

Whether you have a full or an empty stomach can affect how much of a drug gets into your bloodstream.

You should take the right dose, no more or less.

Talk to your healthcare team before you stop taking a cancer drug or if you miss a dose.

When you have exemestane

You take exemestane once a day, usually for a few years.

Tests

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

Side effects

How often and how severe the side effects are can vary from person to person. They also depend on what other treatments you're having. 

When to contact your team

Your doctor, nurse or pharmacist will go through the possible side effects. They will monitor you during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

• you have severe side effects 
• your side effects aren’t getting any better
• your side effects are getting worse

Early treatment can help manage side effects better. 

We haven't listed all the side effects here. Remember it is very unlikely that you will have all of these side effects. But you might have some of them at the same time.

Common side effects

These side effects happen in more than 10 in 100 people (more than 10%). You might have one or more of them. They include:

Increased risk of infection

Increased risk of getting an infection is due to a drop in white blood cells. Symptoms include a change in temperature, aching muscles, headaches, feeling cold and shivery and generally unwell. You might have other symptoms depending on where the infection is.

Infections can sometimes be life threatening. You should contact your advice line urgently if you think you have an infection. 

Difficulty sleeping (insomnia)

It can help to change a few things about how you try to sleep. Try to go to bed and get up at the same time each day and spend some time relaxing before you go to bed. Some light exercise each day may also help. 

Depression

Tell your doctor or nurse if you’re feeling depressed. They can arrange for you to talk to someone and give treatment if necessary.

Headaches and dizziness

Let your doctor or nurse know if you have headaches. They can give you painkillers. Don’t drive or operate machinery if you feel dizzy.

Hot flushes and sweats

We have some tips for coping with hot flushes in women. We also explain some of the possible treatments. Talk to your doctor if your hot flushes are hard to cope with. They might be able to prescribe you some medicines.

Tummy (abdominal) pain

Tell your treatment team if you have this. They can check the cause and give you medicine to help. 

Feeling sick

This is usually mild. Let your doctor or nurse know if you have it.

Liver changes

You might have liver changes that are usually mild and unlikely to cause symptoms. They usually go back to normal when treatment finishes. You have regular blood tests to check for any changes in the way your liver is working.

Sweating

Let your doctor or nurse know if you are sweating much more than normal. There are treatments and things you can do to help control it.

Pain

You may feel pain in different parts of your body such as your muscles and joints. Speak to your doctor or nurse about what painkillers you can take to help with this.

Tiredness and weakness

You might feel very tired and as though you lack energy.

Various things can help you to reduce tiredness and cope with it, for example exercise. Some research has shown that taking gentle exercise can give you more energy. It is important to balance exercise with resting.

Occasional side effects

These side effects happen in between 1 and 10 out of every 100 people (between 1 and 10%). You might have one or more of them. They include:

• bruising, bleeding gums or nose bleeds due to a drop in the number of platelets in your blood
• loss of appetite
• pain in your hands and a weak grip - including numbness and tingling in your hands
• being sick
• diarrhoea or constipation
• indigestion
• hair loss
• skin problems including hives and itchy skin
• thinning of the bones which can lead to small cracks in the bones (fractures)
• pain and swelling of hands and feet

Rare side effects

This side effects happens in fewer than 1 in 100 people (fewer than 1%). You might have one or more of them. They include:

• an allergic reaction which can cause a skin rash, feeling hot and shivering, shortness of breath and dizziness – let your doctor or nurse know if this happens
• feeling very sleepy or drowsy
• inflammation of the liver

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do I need to know?

Other medicines, foods and drinks

Cancer drugs can interact with some other medicines and herbal products. Tell your doctor or pharmacist about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies.

Do not take hormone replacement therapy while you are having exemestane treatment.

The following medicines should be used cautiously when taking exemestane. Let your doctor know if you are taking medicines such as:

• rifampicin (an antibiotic)
• carbamazepine or phenytoin (anticonvulsants used to treat epilepsy)
• St John’s wort - a herbal remedy used as a complementary therapy for mild to moderate depression

Sugar intolerance

This drug contains a type of sugar called sucrose. Tell your doctor if you have an intolerance to any type of sugar.

Pregnancy and contraception

Exemestane might harm a developing baby in the womb. It’s important to use contraception while taking this drug if it’s unclear if you have been through the menopause or you are taking drugs to stop your periods. Talk to your doctor or nurse about effective contraception. They can tell you how long to carry on using contraception after you stop taking exemestane.

Breastfeeding

It is not known whether this drug comes through into the breast milk. Doctors usually advise that you don’t breastfeed during this treatment.

Treatment for other conditions

Always tell other doctors, nurses, pharmacists or dentists that you’re having this treatment. For example, if you need treatment for anything else, including teeth problems.

More information about this treatment

For further information about this treatment go to the electronic Medicines Compendium (eMC) website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

This page is due for review. We will update this as soon as possible.