Sounds like 'let-ro-zole'

Letrozole is used to treat some types of breast cancer. Find out how to take it safely and possible side effects. Letrozole is commonly called Letara or Letrole.

Type of medicine Also called
  • Used for breast cancer in women
  • Belongs to a group of medicines known as aromatase inhibitors
  • Letara®
  • Letrole®

What is letrozole?

Letrozole is used to treat breast cancer in women who have gone through menopause. This type of breast cancer is called oestrogen receptor-positive breast cancer (cancer that grows in response to the hormone oestrogen).

Letrozole is a type of medicine called an aromatase inhibitor. Aromatase is an enzyme that helps the body make oestrogen. Letrozole blocks (inhibits) the activity of aromatase. This reduces the amount of oestrogen in your body, and in this way, slows the cancer's growth.

In New Zealand, letrozole is available as tablets. 


  • The usual dose of letrozole is 1 tablet (2.5 mg) once a day.
  • Letrozole is a long-term treatment; you may have to take it for several years.
  • Always take your letrozole exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions.

How to take letrozole?

  • Take letrozole at the same time each day, either in the morning or the evening. 
  • You can take letrozole with or without food.
  • It is not harmful if you miss a dose of letrozole. If you forget to take your dose, take it as soon as you remember, but if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
  • Do not stop taking letrazole suddenly; speak to your doctor before stopping.

Precautions before starting letrozole

  • Are you still having menstrual periods? If you have not gone through the menopause you should not take letrozole.
  • Do you have osteoporosis (a condition that causes your bones to be thinner and weaker than normal)?
  • Do you have problems with your liver?
  • Do you have high blood pressure or high cholesterol?
  • Are you pregnant or breastfeeding?
  • Are you taking any other medicines, including medicines you can buy without a prescription, such as herbal and complementary medicines?

If any of these apply, it’s important that you tell your doctor or pharmacist before you start letrozole. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

What are the side effects of letrozole?

Like all medicines, letrozole can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Hot flushes and sweats

This is quite common when you are taking letrozole and is often mild, but this can vary. Hot flushes and sweats may improve after the first few months. You can try to reduce this effect by not smoking, reducing alcohol and avoiding hot drinks containing caffeine, such as tea and coffee. Try to dress in layers, so you can remove clothes as needed, and wear clothes made from natural fabrics, such as cotton. If hot flushes are troubling you, tell your doctor or nurse. There are some medicines that can help to reduce flushes.

Other side effects

Side effects What should I do?
  • Nausea, feeling sick or vomiting
  • Try taking letrozole with food or just before bed
  • Tell your doctor if troublesome
  • Increased or reduced appetite
  • Thinning hair
  • Joint pain, stiffness 
  • Feeling tired, or dizzy or have lack of energy 
  • Headache
  • Constipation or diarrhoea (runny poos)
  • Sweating
  • Mood swings
  • Difficulty sleeping
  • These may improve with time 
  • Tell your doctor if troublesome
  • Avoid driving if you feel tired or dizzy
  • Vaginal bleeding 
  • Swollen legs or feet
  • Tingling in the arms or hands
  • Tell your doctor immediately or ring HealthLine 0800 611 116
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product


Letrozole may interact with some medicines and herbal supplements so check with your doctor or pharmacist before starting letrozole or before starting any new medicines or supplements.

Learn more


  1. Letrozole New Zealand Formulary
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 12 Feb 2019