Sounds like 'an-as-tro-zole'

Anastrozole is used to treat breast cancer. Anastrozole is also called Anatrole or Arimidex.

What is anastrozole?

Anastrozole is used to treat some types of breast cancer in women who have gone through menopause. This type of breast cancer is called oestrogen receptor-positive (ER-positive) breast cancer. Anastrozole belongs to a group of medicines called aromatase inhibitors.

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 through a complex process. Aromatase inhibitors are a type of medicine that block this process and reduce the amount of oestrogen in the body. In this way exemestane slows or stops the growth of the cancer cells. Read more about aromatase inhibitors.


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

  • 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.

How to take anastrozole

  • 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 is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
  • Do not stop taking anastrozole suddenly; speak to your doctor before stopping.

Things to consider while you are taking anastrozole

  • 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.
  • 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.
  • If you haven't gone through the menopause yet, let your doctor know. Another option might be better for you.
  • If you have osteoporosis, let your doctor know.

What are the side effects of anastrozole?

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, such as 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 doctor or nurse. 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 troublesome. 
  • 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 troublesome
  • 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

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

Learn more

Arimidex Medsafe Consumer Information


  1. anastrozole NZ Formulary
  2. Breast cancer NZ Formulary
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 12 Jan 2018