Anastrozole for breast cancer - Arimidex

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Take one 1 mg tablet each day.

You can take the tablet before or after food.

The most common side-effects are headache, hot flushes, feeling sick, rash, joint pain, and feeling weak. These can occur in more than 1 in 10 women who take anastrozole.

Type of medicine An aromatase inhibitor
Used for Breast cancer
Also called Arimidex®
Available as Tablets

Treatment options for women with breast cancer include surgery, radiotherapy, chemotherapy and hormone treatment. Often a combination of two or more of these treatments is used. Anastrozole is a hormone treatment.

Some breast cancers need the hormone oestrogen to grow. In women who have been through the menopause, the main source of oestrogen is through the change of sex hormones called androgens into oestrogen. An enzyme called 'aromatase' is needed for this change to occur. Anastrozole works by blocking (inhibiting) this enzyme. This reduces the amount of oestrogen in your body, which slows the growth of the cancer cells.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking anastrozole it is important that your doctor knows:

  • If you are still having menstrual periods - if you have not gone through the menopause you should not take anastrozole.
  • If you have been told you have a loss of bone density (osteoporosis).
  • If you have problems with the way your liver works, or problems with the way your kidneys work.
  • If you have ever had an allergic reaction to a medicine.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines. It is particularly important that your doctor knows if you are taking a medicine called tamoxifen, or any oestrogen-containing medicines such as hormone replacement therapy (HRT).
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about anastrozole and will provide you with a full list of the side-effects which you may experience from taking it.
  • Take one 1 mg tablet of anastrozole each day, exactly as your doctor tells you to. Your dose will be printed on the label of the tablet pack to remind you.
  • You may take anastrozole at whatever time of day you find easiest to remember, but try to take your doses at the same time each day. This will help you to avoid missing any doses.
  • You can take the tablet before or after a meal.
  • If you forget to take a dose, take it as soon as you remember. If you do not remember until the following day, skip the missed dose. Do not take two doses together to make up for a forgotten dose.
  • Try to keep your regular appointments with your doctor or clinic. This is so your doctor can check on your progress. Anastrozole lowers the levels of female hormones in your body, which can reduce the strength of your bones. You will need to have bone density tests (before and during your treatment) to check for this.
  • Anastrozole is a long-term treatment so it's important to continue to take the tablets regularly unless your doctor tells you otherwise. It is likely you will need to take the tablets for five years.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking anastrozole.
  • If you buy any medicines, check with a pharmacist that they are safe to take with your other medicines.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with anastrozole. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common anastrozole side-effects What can I do if I experience this?
Hot flushes Try to keep cool by wearing light, airy clothes
Feeling or being sick, loss of appetite Stick to simple meals - avoid rich or spicy foods
Feeling weak or sleepy This can happen when you first start treatment but quickly settles. Do not drive or use tools or machines if affected
Headache Ask your pharmacist to recommend a suitable painkiller
Diarrhoea Drink plenty of water to replace the lost fluids
Skin rash, joint aches and pains, vaginal dryness or bleeding, hair thinning, carpal tunnel syndrome If any of these become troublesome, speak with your doctor for advice

If you experience any other symptoms which you think may be due to the tablets, speak with your doctor or pharmacist for further advice.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Prof Cathy Jackson
Document ID:
3784 (v26)
Last Checked:
24/11/2014
Next Review:
23/11/2017
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