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Anastrozole (Arimidex)

Anastrozole is a cancer treatment drug and is also known by its brand name, Arimidex.

It is a treatment for post menopausal women with breast cancer that is hormone sensitive.

How anastrozole works

Anastozole lowers the amount of oestrogen in the body. The female sex hormones oestrogen and progesterone stimulate many breast cancers to grow. Lowering the level of oestrogen can stop or slow the growth of breast cancer cells.

Anastrozole blocks a process called aromatisation that changes sex hormones called androgens into oestrogen. This happens mainly in the fatty tissues, muscle and the skin and needs a particular enzyme called aromatase.

How you have it

You have anastrozole as tablets.

Try to take it at the same time each day. Swallow the tablet whole with a drink of water. You can take it before, with, or after food.

If you accidentally take more anastrozole than you should, let your doctor know straight away.

If you forget a dose, continue with the next dose as normal. Don't take an extra dose to make up for the missed one.

Taking tablets

You must take tablets and capsules according to the instructions your doctor or pharmacist gives you.

You should take the right dose, not more or less.

Talk to your specialist or advice line before you stop taking a cancer drug.

When you have anastrozole

You take anastrozole once a day. Try to take it at the same time each day. It is a long term treatment and you usually need to take it for several 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

We haven't listed all the side effects. It is very unlikely that you will have all of these side effects, but you might have some of them at the same time.

How often and how severe the side effects are can vary from person to person. They also depend on what other treatment you are having. For example, your side effects could be worse if you are also having other drugs or radiotherapy.

When to contact your team

Your doctor or nurse will go through the possible side effects. They will monitor you closely 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.

Coping with side effects

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

Common side effects

Each of these effects happens in more than 10 out of 100 people (10%). You might have one or more of them. They include:

Headaches 

Tell your doctor or nurse if you keep getting headaches. They can give you painkillers to help.

Hot flushes

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

Feeling sick 

Talk to the team looking after you about this. 

Skin rash

Skin problems include a skin rash, dry skin and itching. This usually goes back to normal when your treatment finishes. Your nurse will tell you what products you can use on your skin to help.

Painful or stiff joints

You might feel some pain from your muscles and joints. Speak to your doctor or nurse about what painkillers you can take to help with this.

Tiredness and weakness (fatigue) 

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.

Loss of bone strength

Talk to the team looking after you about this. 

Occasional side effects

Each of these effects happens in between 1 and 10 out of 100 people (1 to 10%). You might have one or more of them. They include:

  • allergic reaction
  • diarrhoea
  • vaginal dryness
  • vaginal bleeding
  • hair thinning
  • liver changes
  • being sick
  • carpal tunnel syndrome
  • loss of appetite
  • raised cholesterol in the blood
  • feeling sleepy
  • bone pain

Rare side effects

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

  • liver inflammation (hepatitis)
  • trigger finger (finger or thumb fixed in a bent position)

What else do I need to know?

Other medicines, foods and drink

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.

Pregnancy and contraception

This treatment might harm a baby developing in the womb. It is important not to become pregnant or father a child while you're having treatment and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.

Breasfeeding

Don’t breastfeed during this treatment because the drug may come through into your breast milk.

Treatment for other conditions

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

Anastrazole for men

Anastrozole might sometimes be used to treat breast cancer in men. Breast cancer is very rare in men. So very little is known about the side effects of this drug in men. Doctors expect the effects to be similar to those listed on this page.

lactose

This drug contains lactose (milk sugar). If you have an intolerance to lactose, contact your doctor before taking this medicine.

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.

Information and help

Dangoor sponsorship

About Cancer generously supported by Dangoor Education since 2010.