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Femara Print


Generic name: Letrozole
Trade name: Femara
Other names:
Drug type:

Letrozole is also called Femara. It is a type of hormone therapy drug called an aromatase inhibitor, and is used to treat breast cancer

Many breast cancers are stimulated to grow by the female sex hormones oestrogen and progesterone. These breast cancers are called ‘hormone sensitive’ or ‘hormone receptor positive’ and can be treated with drugs that block the effects of these hormones.

Although women who have had their menopause don’t produce oestrogen from their ovaries, they still produce a small amount by turning other sex hormones (androgens) into oestrogen. Androgens are made by your adrenal glands, the small glands above your kidneys. Androgens need an enzyme called aromatase to turn them into oestrogen. This change happens mainly in fatty tissue, muscle and the skin. Aromatase inhibitors stop or ‘inhibit’ aromatase, so it can’t change the androgen into oestrogen. These drugs are only suitable for women who've had their menopause.

You take letrozole as a tablet, once a day.

There is general information about hormone therapies in the cancer treatment section.

We've listed the side effects associated with letrozole below. You can use the links to find out more about each side effect. Where there is no link, please click on search at the top of the page.

Common side effects

Many women will have one or more of the following side effects

  • Hot flushes and sweats - this happens in about 3 out of 10 women treated (30%)
  • Painful joints - this affects about 1 out of 5 women treated (20%)
  • Tiredness or fatigue - about 1 in 5 women treated (20%) get this side effect

Occasional side effects

  • Skin rashes - these are usually mild. You should let your doctor know if you have a rash. This happens in about 1 in 10 (10%) women having this treatment
  • Headaches - in about 1 in 10 women (10%)
  • Dizziness occurs in around 1 in 10 women (10%)
  • Feeling or being sick - this is usually mild and can be easily controlled by anti sickness tablets, or if necessary injections. It affects about 1 in 10 women treated (10%).
  • Fluid retention causing ankle and or finger swelling. This affects about 1 in 10 women treated (10%).
  • Loss of appetite or indigestion
  • Hair thinning
  • Diarrhoea - if this happens it is usually mild. You should drink plenty of fluids. If it gets severe or persistent you could become dehydrated, so you should tell your doctor or nurse. Some people get constipation
  • Vaginal dryness
  • Decreased interest in sex (reduced libido)
  • Feeling low in mood
  • Cough and breathlessness - this affects less than 1 in 10 (10%) of women having letrozole
  • Increased levels of cholesterol in the blood. This is usually only slightly increased. You will have regular blood tests to check this.
  • Loss of bone density - this is caused by a lack of oestrogen over a long period of time. When your bones are less ‘dense’ they may break more easily. You should have a 'DEXA scan' to check your bone density before you start treatment.
  • Vaginal bleeding. This mainly happens when women have changed from one type of hormone therapy to another during the first few weeks of treatment. You should tell your doctor or nurse if the bleeding continues. This affects fewer than 1 in 20 (5%) women treated.

Important points to remember

The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment, or more side effects may develop as the course goes on. This depends on

  • How many times you've had the drug before
  • Your general health
  • The amount of the drug you have (the dose)
  • Other drugs you are having

Some side effects are inconvenient or upsetting but not damaging to your health.

Some side effects are serious medical conditions and need treating. Where we have urged you to contact your doctor, this is because

  • Your side effect may need treating
  • Your drug dose may need reducing to try to prevent the side effect

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and other over the counter remedies - some drugs can react together.Talk to your doctor, pharmacist or nurse about all your side effects so that they can help you manage them. You should have a contact number for your chemotherapy nurse, clinic or ward nurse. You can ring if you have any questions or problems. They can give you advice or reassure you. If in doubt, call them.

Last Updated on Thursday, 21 January 2010 09:25