How does letrozole work?
Letrozole belongs to a group of medicines called aromatase inhibitors.
Aromatase inhibitor medicines are used to treat certain types of breast cancer where the cancer cells need oestrogen (a hormone) in order to grow.
After the menopause, your ovaries stop producing oestrogen. Instead, your body makes oestrogen from an enzyme called aromatase.
Aromatase inhibitors reduce the amount of aromatase in your body and this stops your body producing oestrogen. This helps prevent cancer cells growing, as they no longer have anything to feed on.
When will I feel better?
Letrozole will start to reduce the amount of oestrogen in your body immediately.
However, it takes several weeks or months for the medicine to work fully.
During this time you're likely to have menopause symptoms as your body gets used to having less oestrogen. These symptoms will gradually improve as your body adjusts to the medicine.
Are there any long-term side effects?
Letrozole is generally safe to take for a long time. However, your specialist team will monitor your health carefully.
This is because letrozole reduces levels of oestrogen in your body. Your body needs oestrogen for strong and healthy bones. If you take letrozole for a long time your bones can become weaker (osteoporosis) and more likely to break.
You may have bone density scans before you start taking letrozole, 1 or 2 years into treatment and again after you finish your treatment.
Your doctor may recommend a type of medicine called a bisphosphonate to help reduce bone damage. They can also give you advice on exercise and diet to help keep your bones strong.
Letrozole can also increase your blood pressure and cholesterol levels. Your doctor will monitor these during your regular check-ups and will recommend treatment if you need it.
What will happen if I stop taking it?
If you want to stop taking letrozole for any reason, your doctor will be able to discuss alternatives for treating your breast cancer or preventing it coming back.
Sometimes people are given a short break from letrozole. This can help if you're getting side effects such as joint pain. However, only take a break from your medicine if you've discussed it with your specialist first and they agree to it.
Important
Do not stop taking letrozole without talking to your doctor first.
Are there other medicines like letrozole?
Medicines such as tamoxifen, anastrozole and exemestane work in a similar way to letrozole. These medicines lower your oestrogen levels and can cause similar side effects.
However, medicines affect people in different ways. If you're bothered by side effects from taking letrozole, talk to your doctor. They may want to try you on one of these other medicines instead.
What are the benefits of taking letrozole?
Letrozole helps stop your breast cancer coming back. By taking this medicine for 5 years (or sometimes up to 10 years), you have a better chance of being alive 15 years after your breast cancer was first diagnosed.
Your specialist will be able to explain the benefits and risks of taking letrozole.
They can also calculate how well letrozole is likely to work for you. This is done by comparing your details with those of more than 20,000 other people who have had treatment for breast cancer.
The exact benefits and how well it's likely to work for you depend on a combination of different things.
This varies for each person and includes factors like your age when the breast cancer was found, how it was found and whether you've had chemotherapy or not.
Will it affect my contraception?
Letrozole is generally only given to you if you've gone through the menopause.
However, some people find they start having periods again after taking letrozole. If this happens to you, it's important to use reliable contraception. Talk to your doctor if your periods start again, or if there's any chance that you're pregnant.
Letrozole is not recommended during pregnancy.
Can I drive or ride a bike?
Some people feel extremely tired when taking letrozole.
If you feel tired or dizzy, or if you get blurred vision, do not drive, cycle or use machinery or tools until you feel better.
It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.
Talk to your doctor or pharmacist if you're unsure whether it's safe for you to drive while taking letrozole. GOV.UK has more information on the law on drugs and driving.
Can I drink alcohol while taking letrozole?
There's no evidence that drinking alcohol causes any problems when taking letrozole.
Some people taking letrozole may get hot flushes or redness when they drink alcohol. In this case, avoiding alcohol may help.
Is there any food or drink I need to avoid?
Most people can eat and drink normally when taking letrozole.
Some people may get hot flushes or redness when they drink alcohol.
Some people find letrozole affects their appetite.
If you lose your appetite, try to make sure you have a balanced diet. Try eating smaller meals more often.
If it makes you feel hungrier and you're putting on too much weight, ask your doctor or specialist nurse to refer you to a dietitian.