Letrozole for breast cancer (Femara)

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Take one 2.5 mg letrozole tablet every day.

You can take the tablets before or after meals.

The most common side-effects of treatment are hot flushes, sweating, joint pain, and feeling tired. These can occur in more than 1 in 10 people who take letrozole.

Type of medicineAn aromatase inhibitor hormone antagonist
Used forBreast cancer
Also calledFemara®
Available asTablets

Letrozole is known as a hormonal breast cancer treatment.

Some breast cancers need the hormone oestrogen to grow. In women who have been through the menopause, the main source of oestrogen is through the change of sex hormones called androgens into oestrogen. An enzyme called 'aromatase' is needed for this change to occur. Letrozole works by inhibiting (or blocking) this enzyme. This reduces the amount of oestrogen in your body, which slows the growth of the cancer cells.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking letrozole it is important that your doctor knows:

  • If you have not yet gone through the menopause, or if there is a possibility you might be pregnant.
  • If you have problems with the way your liver works, or the way your kidneys work.
  • If you have osteoporosis (a loss of bone density, or 'brittle bones').
  • If you have ever had an allergic reaction to a medicine.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The manufacturer's leaflet will give you more information about letrozole and a full list of the side-effects which you may experience from taking it.
  • Take one 2.5 mg tablet of letrozole each day, exactly as your doctor tells you to. Your dose will be printed on the label of the tablet pack to remind you.
  • You may take letrozole at whatever time of day you find easiest to remember, but try to take your doses at the same time each day. This will help you to avoid missing any doses.
  • You can take the tablets before or after your meals.
  • If you forget to take a dose, take it as soon as you remember. If you do not remember until the following day, skip the missed dose. Do not take two doses together to make up for a forgotten dose.
  • Try to keep your regular appointments with your doctor or clinic. This is so your doctor can check on your progress. Letrozole lowers the levels of female hormones in your body, which can reduce the strength of your bones. You will need to have bone density tests before and during your treatment to check for this.
  • Letrozole is a long-term treatment so it's important to continue to take the tablets regularly unless your doctor tells you otherwise.
  • If you are having an operation or dental treatment, tell the person carrying out the treatment that you are taking letrozole.
  • If you buy any medicines, check with a pharmacist that they are safe to take with your other medicines.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with letrozole. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common letrozole side-effects
What can I do if I experience this?
Hot flushes, sweatingTry to keep cool by wearing light, airy clothes
Headache, muscle or joint painAsk your doctor or pharmacist to recommend a suitable painkiller
Feeling tired, weak or dizzyDo not drive or use tools or machines until you feel better
Feeling or being sick, indigestion, abdominal painStick to simple meals - avoid rich or spicy foods
ConstipationTry to eat a well-balanced diet and drink several glasses of water each day
DiarrhoeaDrink plenty of water to replace lost fluids
Appetite changes, weight changes, feeling depressed, hair loss, skin rash, swollen legs or feet, vaginal bleedingSpeak with your doctor if any of these become troublesome
High blood levels of cholesterol, high blood pressureYour doctor will arrange for you to have tests to check for these

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

  • Manufacturer's PIL, Femara® 2.5 mg Tablets; Novartis Pharmaceuticals UK Ltd, The electronic Medicines Compendium. Dated May 2013.
  • British National Formulary; 66th Edition (September 2013) British Medical Association and Royal Pharmaceutical Society of Great Britain, London

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Prof Cathy Jackson
Document ID:
3745 (v24)
Last Checked:
Next Review:
The Information Standard - certified member

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