Sounds like 'an-as-tro-zole'

Key points about anastrozole

  • Anastrozole is used to treat breast cancer.
  • Anastrozole is also called Anatrole or Arimidex
  • Find out how to take it safely and possible side effects.
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Anastrozole belongs to a group of medicines called aromatase inhibitors and is used to treat some types of breast cancer in women who have gone through menopause. These types of breast cancer are called oestrogen receptor-positive (ER-positive) breast cancers. 

After menopause, the ovaries no longer produce oestrogen but it continues to be made at low levels in fat and other tissues. This happens when an enzyme called aromatase changes other hormones into oestrogen. Aromatase inhibitors are a type of medicine that block this process and reduce the amount of oestrogen in the body. In this way anastrozole slows or stops the growth of the cancer cells. Read more about aromatase inhibitors.

In Aotearoa New Zealand anastrozole is available as tablets (1mg).

  • The usual dose of anastrozole is 1 tablet once a day.
  • Anastrozole is a long-term treatment; you may have to take it for several years.
  • Always take anastrozole exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions.

  • Take anastrozole at the same time each day, either in the morning or the evening. 
  • You can take anastrozole with or without food.
  • If you forget to take your dose, take it as soon as you remember. But if it's nearly time for your next dose, just take the next dose at the right time. Don't take double the dose.
  • Don't stop taking anastrozole suddenly; talk to your doctor before stopping.

Here are some things to know when you're taking anastrozole. Other things may be important as well, so ask your healthcare provider what you should know about.

  • Anastrozole can make you drowsy, especially when you first start taking it. Avoid driving and doing other tasks where you need to be alert until you know how this medicine affects you. It's best to take it at bedtime if it makes you drowsy. Limit alcohol intake, this can make drowsiness worse.
  • Anastrozole can interact with some other medicines and herbal supplements, so check with your doctor or pharmacist before starting anastrozole and before starting any new products.
  • Aromatase inhibitors, such as anastrozole, may decrease bone mineral density (BMD) if you have been through menopause. This means you have a possible increased risk of fractures. You can help to keep your bones strong by regular weight-bearing exercise, eating a healthy diet rich in calcium and vitamin D and not smoking. If you are concerned, talk to your doctor about your risk. .

Like all medicines, anastrozole can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

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. You can try to reduce hot flushes and sweats by not smoking, reducing alcohol and avoiding hot drinks containing caffeine, eg, tea and coffee. Try to dress in layers, so you can remove clothes as needed, and wear clothes made from natural fabrics, such as cotton. If hot flushes are troubling you, tell your healthcare provider. There are some medicines that can help to reduce flushes.

Other side effects

Side effects What should I do?
  • Stomach upset
  • Nausea (feeling sick)
  • Diarrhoea (runny poo)
  • Try taking anastrozole with food or just before bed.
  • Tell your doctor if they bother you.
  • Feeling tired, lack of energy
  • Sleep problems
  • Aching or pain in the joints or muscles
  • Vaginal dryness
  • Headache
  • Hair thinning
  • These may improve with time.
  • Tell your doctor if they bother you.
  • Do not drive if drowsy.
  • Low mood
  • Tell your doctor.
  • Skin rashes, itching, swelling of the face, lips or mouth.
  • Vaginal bleeding
  • Tell your doctor immediately or ring HealthLine 0800 611 116.
For more information on side effects, see the Medsafe consumer information leaflet Arimidex.(external link)

Did you know that you can report a medicine side effect to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product(external link)

Arimidex(external link) Medsafe Consumer Information


  1. Anastrozole(external link) NZ Formulary
  2. Breast cancer(external link) NZ Formulary


5 questions to ask about your medications

5 questions to ask about your medications
Health Quality and Safety Commission, NZ, 2019

Aromatase inhibitors
Breast Cancer Foundation, NZ

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Angela Lambie, Pharmacist, Auckland

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