Exemestane (Aromasin®)

Exemestane is a hormonal therapy drug used to treat breast cancer.

You have exemestane as tablets. Your cancer doctor or nurse will tell you how long you take it for.

Like all hormonal therapy drugs, exemestane can cause side effects. Some of these can be serious so it’s important to read the detailed information below. How hormonal therapy affects people varies from person to person. Your doctor or nurse can talk to you more about this and give you advice on how to manage side effects.

Tell your doctor or nurse straight away if you feel unwell or have severe side effects, including any we don’t mention here. If you need to see a health professional for any reason other than cancer, always tell them that you are having this treatment.

How exemestane works

Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies are drugs that interfere with the way hormones are made or how they work in the body.

Many breast cancers rely on the hormone oestrogen to grow. This type of breast cancer is called oestrogen receptor-positive (ER positive) breast cancer.

In women, after the menopause, oestrogen is no longer made in the ovaries. Instead, it is made in the fatty tissues of the body. This happens when an enzyme (a type of protein) called aromatase changes other hormones into oestrogen. Exemestane is a type of drug called an aromatase inhibitor. It blocks (inhibits) the activity of aromatase and reduces the amount of oestrogen in the body.

When exemestane is given

Exemestane is used to treat breast cancer in women who have been through the menopause. Sometimes it’s used to treat breast cancer in men.

Exemestane may be used after other treatments to reduce the risk of breast cancer coming back. You will usually take it after having two or three years of another hormonal therapy called tamoxifen.

Exemestane may also be used after other hormonal therapies, to control breast cancer that has spread to other parts of the body (secondary breast cancer).

Your doctor or nurse will explain how long you should take exemestane for.

Taking your tablets

You take exemestane as a tablet once a day after food. You take it at the same time each day, whether that is in the morning or in the evening.

Do not stop taking any of your tablets unless your doctor tells you to. Here are some important things to remember:

  • If you forget to take your tablets, just take your usual dose the next day. Don’t take a double dose.
  • Keep tablets in the original package and at room temperature, away from heat and direct sunlight.
  • Keep them safe and out of the sight and reach of children.
  • Get a new prescription before you run out of tablets and make sure you have plenty for holidays.
  • Return any remaining tablets to the pharmacist if your treatment is stopped.

Possible side effects of exemestane

We explain the most common side effects of exemestane here. We also include some rarer side effects. You may get some of the side effects we mention, but you are very unlikely to get all of them. If you are having other drugs as well, you may have some side effects that we don’t list here.

You will see a doctor or nurse regularly while you have this treatment. Always tell your doctor or nurse about the side effects you have. They can prescribe drugs to help control them and give you advice about managing them. Don’t stop taking exemestane without talking to your doctor first.

More information about this drug

We’re not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the electronic Medicines Compendium (eMC).

Hot flushes and sweats

These are common and are often mild, but this can vary. Hot flushes and sweats may improve after the first few months. Cutting down on nicotine, alcohol and hot drinks containing caffeine, such as tea and coffee, can help. Dress in layers, so you can remove clothes as needed. Natural fabrics, such as cotton, may feel more comfortable.

If hot flushes are troublesome, tell your doctor. Low doses of certain antidepressant drugs can help to reduce them.

We have more information for women and information for men about coping with hot flushes.

Joint and muscle pain

You may have pain and stiffness in your joints, and sometimes in your muscles, while taking exemestane. Let your doctor and nurse know if this happens. They can prescribe painkillers and give you advice. Being physically active and maintaining a healthy weight can help to reduce joint pain and keep joints and muscles flexible. Let your doctor know if it doesn’t get better.

Feeling sick, indigestion or tummy pain

Any sickness is usually mild, but let your doctor or nurse know if this happens. Try taking your exemestane tablets with food or at night. Exemestane may also cause indigestion or tummy pain. Let them know if you have any of these symptoms. They can prescribe drugs to help. If you don’t have an appetite, try to eat lots of small meals or snacks regularly.

Tiredness and lack of energy

You may feel tired, sleepy or as though you have no energy when you start taking exemestane. Try to pace yourself until this improves. It’s important to get the right balance of having enough rest and being physically active. Going for regular short walks will help you to feel less tired. If you feel sleepy, don’t drive or use machinery.


If you have headaches, let your doctor or nurse know. They can usually be controlled with mild painkillers.

Diarrhoea or constipation

Diarrhoea is usually mild. If it doesn’t get better, your doctor can prescribe drugs to control it. Make sure you drink at least two litres (three and a half pints) of fluid every day if you have diarrhoea.

Exemestane can also cause constipation. Drinking at least two litres (three and a half pints) of fluids every day will help. Try to eat more foods that contain fibre (such as fruit, vegetables and wholemeal bread) and do some regular gentle exercise.

Difficulty sleeping and mood changes

If you have trouble getting to sleep, try having a warm bath or a hot milky drink before bed. Relaxation techniques, tapes or CDs can also help. Some people may feel low in mood or become depressed while taking exemestane. Talk to your nurse or doctor if this happens. They can suggest ways to help with this.

Skin rashes

You may get a mild skin rash. Tell your doctor or nurse if this happens. It’s very important to contact your doctor straight away if you get a severe skin rash.

Hair thinning

Some people notice that their hair becomes thinner while taking exemestane. This is usually mild. Your hair will get thicker after treatment finishes.

Feeling dizzy

Exemestane may cause dizziness. Let your doctor or nurse know if this is a problem.

Pain, numbness and tingling in hand and fingers

These symptoms may be due to carpal tunnel syndrome, which is caused by pressure on a nerve in the wrist. It’s more common in people taking exemestane. Tell your doctor if you have these symptoms.

Build-up of fluid

You may put on weight or your ankles and legs may swell because of fluid building up. Tell your doctor or nurse if this happens. If your ankles and legs swell, it can help to put your legs up on a foot stool or cushion.

Liver changes

Exemestane may cause changes in the way your liver works. You are very unlikely to notice any problems. Your doctor will take regular blood samples to check your liver is working properly.

Rarely, exemestane causes inflammation of the liver (hepatitis). Tell your doctor straight away if the whites of your eyes or your skin turn yellow, or if you become unwell with itching, or pain on the right side of your tummy.

Possible side effects of long-term exemestane treatment

Bone thinning

Taking exemestane for a few years increases your risk of bone thinning, which is called osteoporosis. This can increase your risk of a broken bone (fracture). You will usually have bone density scans to check your bone thickness before and during treatment. If you are at risk of osteoporosis, your doctor may prescribe drugs called bisphosphonates to protect your bones. They will also usually advise you to take calcium and vitamin D supplements. Regular walking, eating a healthy diet, not smoking and sticking to sensible drinking guidelines will also help. We have more information about how cancer treatments may affect bone health.

Side effects can usually be controlled or improved. Always let your doctor or nurse know about any side effects you have so they can help you feel better.

Other information about exemestane

If you have ongoing problems

Most of the time side effects can be controlled or managed. But for a few people, they can be more troublesome. If this happens, make sure you talk to your cancer doctor or nurse. They can usually suggest ways to improve your side effects. If things don’t improve, go back to your doctor or nurse. They may suggest you try something else.

It’s important not to stop taking exemestane without telling your doctor, as this may affect the success of your treatment. If side effects can’t be managed, your cancer doctor may suggest you take a different type of hormonal therapy.

Other medicines

Exemestane can interact with other drugs. This includes medicines you can buy in a shop or chemist. Tell your doctor about any medicines you are taking, including ones you can buy for yourself, complementary therapies, and herbal drugs such as St John’s wort.

Problems with glucose

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

Medical or dental treatment

If you need to go into hospital for any reason, always tell the doctors and nurses that you are taking exemestane. Explain you are taking hormonal therapy and that no one should stop or restart it without checking with your cancer doctor first. Tell them the name of your cancer doctor so they can ask for advice.

Always tell your dentist you are taking exemestane before having any dental treatment.