Anastrozole

What is anastrozole?

Anastrozole, sometimes known by the brand name Arimidex, is a prescription-only medicine used to treat hormone receptor-positive breast cancer. It belongs to a group of drugs called aromatase inhibitors, which work by lowering the amount of oestrogen in the body[1]. 

What is anastrozole used for?

Anastrozole is used for the following[1]: 

• Treating early and advanced breast cancer in postmenopausal women 

• Helping to prevent breast cancer in women at moderate or high risk due to family history or genetic factors 

• Occasionally treating breast cancer in men, usually alongside other hormone therapies 

How does anastrozole work?

Anastrozole works by blocking an enzyme called aromatase. This enzyme helps convert androgens (male hormones) into oestrogen in postmenopausal women. Since some breast cancers rely on oestrogen to grow, reducing oestrogen levels can slow or stop tumour growth[1]. 

Who can take anastrozole?

Anastrozole is suitable for most adults over the age of 18. However, you should tell your doctor first if you[1]: 

• Are pregnant, trying to get pregnant, or breastfeeding 

• Still have regular periods (not yet postmenopausal) 

• Have severe liver or kidney problems 

• Have osteoporosis or are at risk of fractures 

• Are allergic to anastrozole, lactose, or any other ingredient in the medicine 

Please tell your doctor or pharmacist about any conditions you may have or medication you take before you start treatment, and always follow the instructions in the Patient Information Leaflet[2].  

What is the typical dosage of anastrozole?

Anastrozole comes as 1mg tablets. The typical dosage is 1mg tablet taken once a day. Treatment usually continues for 5 years, but your doctor or pharmacist may recommend a different length of treatment depending on your situation[1]. 

How do you take anastrozole?

To take anastrozole correctly[1]: 

• Take one tablet at the same time each day 

• Swallow it whole with a glass of water – do not chew or crush 

• You can take it with or without food 

Can you stop taking anastrozole?

Do not stop taking anastrozole without speaking to your pharmacist or doctor. If you are having side effects, they may[1]: 

• Recommend a temporary break from treatment 

• Switch you to another aromatase inhibitor 

What do you do if you take too much anastrozole?

If you take more anastrozole than prescribed and begin to feel unwell (such as nausea or vomiting), do the following[1]: 

• Call NHS 111 or go to your nearest A&E 

• Take the medicine packaging with you to show them 

What do you do if you forget to take anastrozole?

If you forget to take a dose[1]: 

• Skip it and take the next dose at your usual time 

• Do not take a double dose to make up for the missed one

What medicines can’t you take with anastrozole?

There are very few medicines that affect the way anastrozole works. But you should avoid taking anastrozole with the following[1]: 

• Hormone replacement therapy (HRT) 

• Medicines used to treat breast cancer (selective oestrogen receptor modulators), e.g., medicines that contain tamoxifen 

• Any medicines or supplements containing oestrogen such as hormonal contraceptives 

• Herbal menopause remedies such as black cohosh or red clover 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[2]. 

What are the side effects of anastrozole?

Common side effects (affecting more than 1 in 100 people) include: 

• Hot flushes and sweating 

• Joint and muscle pain 

• Tiredness or low mood 

• Vaginal dryness, bleeding, or spotting 

• Sleep problems 

• Nausea or reduced appetite 

• Numb or tingling extremities 

• Mild rash or skin changes 

• Hair loss or thinning 

• Bone thinning (osteoporosis) with long-term use 

Less common but more serious side effects include[1]: 

• Liver problems (eye or skin yellowing) 

• Red, purple, or dark, spots on your skin, painful joints, stomach ache or pain in your side, back, or around your genitals as a sign of Henoch-Schonlein purpura 

• Bone fractures 

• Low calcium levels (increased thirst, peeing, and nausea) 

You should contact your GP if you experience any of these symptoms. In rare cases, the medicine may cause a serious allergic reaction (anaphylaxis). You should call 999 or visit A&E immediately if you believe this is happening[1]. 

Symptoms of anaphylaxis include[1]:  

• Difficulty breathing  

• Tightness in throat and chest  

• Swelling of the tongue or throat  

• Feeling faint or dizzy  

• Blue/grey skin or lips  

• Loss of consciousness 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice. 

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[2]. 

Frequently asked questions about anastrozole

How long does anastrozole take to work? 
It begins reducing oestrogen within 24 hours, but full effects may take several weeks or months[1]. 

Can I drink alcohol while taking anastrozole? 
Yes, in moderation. Be aware that alcohol may worsen hot flushes or tiredness[1]. 

Can I drive while taking anastrozole? 
Yes, unless you feel dizzy or very tired. Use caution until you know how it affects you[1]. Do not drive should you feel drowsy or tired. 

For the official NHS guide to anastrozole, visit their website.