Letrozole is a medicine used for treating breast cancer. It can also help prevent breast cancer coming back.

It is mainly prescribed for women who have been through the menopause and have a type of cancer called "hormone-dependent" breast cancer.

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

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

Letrozole 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 and younger women
• as a fertility treatment if you have polycystic ovary syndrome

• You usually take letrozole once a day – try to take it at the same time each day.
• Most people are given letrozole for 5 years, but some will take it for up to 10 years.
• 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.

Letrozole can be taken by adults only (aged 18 years and over).

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

• have had an allergic reaction to letrozole 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)

Letrozole comes as 2.5mg tablets. The usual dose is 1 tablet, taken once a day.

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

Swallow the tablet whole with a drink of water. Do not crush or chew it. You can take letrozole with or without food.

What if I forget to take it?

If you forget a dose take it as soon as you remember, unless your next dose is due in 2 or 3 hours. In this case skip the missed dose and take your next one at the usual time.

Do not take a double dose to make up for a forgotten dose.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice about other ways to help you remember to take your medicine.

What if I take too much?

If you take too many letrozole tablets by accident, you may get symptoms like feeling sick, blurred vision or a fast heartbeat.

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

Common side effects

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

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

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

• hot flushes and sweating
• dry or itchy vagina, 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
• low mood or depression

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

Serious side effects

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

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

Letrozole is not recommended when pregnant or breastfeeding. This is because it can harm your baby.

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

There are very few medicines that interfere with the way letrozole works in the body.

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

Mixing letrozole with herbal remedies and supplements

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

There's very little information about taking other herbal remedies and supplements together with letrozole.