Anastrozole is a type of hormone treatment. It works by lowering the levels of oestrogen hormones in your body.

It is mainly prescribed for women who have been through the menopause and have a type of cancer called hormone-dependent breast cancer. It can sometimes also be used:

• to prevent breast cancer if you are high risk and have been through the menopause
• to treat breast cancer in men
• to treat breast cancer in younger women before the menopause
• as a fertility treatment if you have polycystic ovary syndrome

Most people who take anastrozole will have had surgery, radiotherapy or sometimes chemotherapy to treat their breast cancer first.

Anastrozole is available on prescription only. It comes as tablets.

• You usually take anastrozole once a day. Try to take it at the same time each day, as this makes it easier to remember.
• Treatment with anastrozole usually lasts for up to 5 years. It is important to complete your course of treatment.
• Common side effects can be like menopause symptoms and include hot flushes, difficulty sleeping, tiredness and low mood.
• Side effects usually improve after a few months as your body gets used to the medicine.
• Your doctor will monitor your blood pressure, cholesterol levels and bone density during your treatment.

Anastrozole is not suitable for some people. Tell your doctor before starting on this medicine if you:

• have had an allergic reaction to anastrozole or any other medicines in the past
• still have periods
• are pregnant, trying to get pregnant or breastfeeding
• have serious kidney or liver disease
• have been told you have fragile or brittle bones (osteoporosis)

Swallow the tablet whole with a drink of water. Do not crush or chew it.

You can take anastrozole with or without food.

Dosage

Anastrozole comes as 1mg tablets. The usual dose is 1 tablet, taken once a day.

Try to take your anastrozole at the same time each day, this will make it easier to remember. You can choose a time that suits your everyday routine

What if I forget to take it?

If you forget to take your medicine, just skip the missed dose. Take your next dose at the normal time.

Do not take a double dose to make up for a forgotten one. If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.

What if I take too much?

If you take too many anastrozole tablets, you may get symptoms like feeling sick, vomiting or diarrhoea.

Like all medicines, anastrozole can cause side effects, although not everyone gets them.

Anastrozole may affect your blood pressure, cholesterol and bone density. Your doctor will monitor this carefully and can recommend additional treatment if needed.

Common side effects

Menopause symptoms usually improve during the first few months of taking anastrozole.

These common side effects happen in more than 1 in 100 people.

• hot flushes and sweating
• dry or itchy vagina and genitals, bleeding from your vagina
• difficulty sleeping
• feeling very tired
• feeling or being sick, loss of appetite
• mild aches in your muscles and bones
• numb or tingling hands
• changes to your skin, including a mild rash
• hair loss or thinning hair
• low mood or depression

Talk to your doctor or a pharmacist if these side effects bother you or do not go away:

Serious side effects

Serious side effects are rare and happen in less than 1 in 100 people.

Tell a doctor if:

• your muscles feel weak, or the joints or tendons in your ankles, legs, shoulders or arms feel weak, painful or swollen
• your skin or the whites of your eyes turn yellow – this can be a sign of liver problems
• your eyesight becomes blurry
• you’re feeling thirsty and peeing a lot, feeling sick and have lost your appetite – you may need a blood test to check your calcium levels
• you get red or purple spots (if you have light skin) or dark spots (if you have darker skin), painful joints, stomach ache, or pain in your side (below your ribs), lower back or around your genitals – these can be signs of Henoch-Schönlein purpura (HSP), a condition affecting your blood vessels

In rare cases, it's possible to have a serious allergic reaction (anaphylaxis) to anastrozole.

Menopause symptoms such as hot flushes, difficulty sleeping, tiredness and low mood usually improve during the first months of taking anastrozole. However, if they are severe or last longer than a few months, talk to your doctor or breast cancer nurse.

What to do about:

• hot flushes and sweating – try cutting down on spicy food, caffeine, smoking and alcohol. It may help to keep the room cool and use a fan. Try spraying your face with cool water, or sipping a cold drink.
• dry or itchy vagina, bleeding from your vagina – ask your doctor or breast cancer nurse to recommend a vaginal moisturiser for treating irritation or dryness. Vaginal bleeding usually happens in the first few weeks after starting anastrozole. Talk to your doctor if it lasts longer than a few days. Also talk to your doctor if these symptoms first appear more than a few weeks after you start taking anastrozole.
• difficulty sleeping – avoid caffeine (tea, coffee, cola and chocolate) in the afternoon and evening. Keep your bedroom dark and quiet, and try going to bed and getting up at a set time each day. It may also help to stop watching TV, looking at your mobile phone or using other electronic devices (like tablets), at least 1 hour before bedtime.
• feeling very tired – gentle exercise and eating healthily can help make you feel less tired. Try going to bed and getting up at a set time each day. Do not drive, ride a bike or operate machinery if you feel very tired while taking anastrozole. This will usually start to improve as your body gets used to the medicine. Speak to your doctor if it does not get better.
• feeling or being sick, loss of appetite – it might help to take anastrozole after you've eaten. Choose foods you normally enjoy but avoid rich or spicy food. Try eating smaller meals but more often. If you're being sick, have small, frequent sips of water to avoid dehydration. Talk to your doctor if your symptoms do not improve or get worse.
• mild aches in your muscles or bones – ask a pharmacist to recommend a suitable painkiller. If the pain lasts more than a week, ask your doctor for advice. If you have a sudden attack of pain in a joint ask a doctor for advice urgently.
• numb or tingling hands – stop taking the medicine and ask your doctor for advice
• changes to your skin, including a mild rash – it may help to take an antihistamine. You can buy these at a pharmacy without a prescription. Check with a pharmacist to see what's suitable for you.
• hair loss or thinning hair – some people find that their hair gets thinner when they start taking anastrozole. This is usually mild. Ask your breast cancer nurse for advice if this is bothering you.
• low mood or depression – it is difficult to know whether this is due to the medicine or a response to menopausal symptoms or being diagnosed with cancer. Speak to your doctor or specialist nurse. They may recommend therapies, like cognitive therapy and mindfulness, or antidepressant medicines.

Anastrozole is not recommended when pregnant or breastfeeding, because it interferes with hormone levels in you and your baby. And there is not enough information available to say if it's safe.

Talk to your doctor straight away if there is any chance that you could be pregnant.

There are very few medicines that affect the way anastrozole works in the body.

However, do not take hormone replacement therapy (HRT) or any other medicines that relieve menopausal symptoms. These may contain ingredients similar to the hormone oestrogen and could stop anastrozole working as well as it should in treating your cancer.

Mixing anastrozole with herbal remedies and supplements

Do not take any herbal remedies or supplements for menopausal symptoms while taking anastrozole. These can stop anastrozole working as well as it should.

There is very little information about taking other herbal remedies and supplements together with anastrozole.