letrozole at a glance
Medicine class
Non-steroidal aromatase inhibitor
Licensed role
Endocrine treatment for selected hormone-dependent breast cancers after the menopause
Administration
Swallow the film-coated tablet whole with water, with or without food
Important monitoring
Bone health, blood pressure and cholesterol may require monitoring
What is letrozole used for?
The selected product is licensed for these breast-cancer settings. Fertility treatment is a separate, non-licensed use requiring specialist supervision.
Additional treatment after primary treatment for hormone-receptor-positive invasive early breast cancer in postmenopausal women.
Extended additional treatment after previous tamoxifen for hormone-dependent invasive breast cancer in postmenopausal women.
First-line treatment of hormone-dependent advanced breast cancer after the menopause.
Advanced breast cancer after relapse or progression in women with postmenopausal endocrine status who previously received anti-oestrogen treatment.
Treatment before surgery for hormone-receptor-positive, HER2-negative breast cancer after the menopause when chemotherapy is unsuitable and immediate surgery is not indicated.
Non-licensed use: fertility specialists may use letrozole to induce ovulation.
How does letrozole work?
Aromatase converts androgen hormones into oestrogens, the main source of oestrogen after the menopause. Letrozole blocks this enzyme, reducing stimulation of breast cancers that depend on oestrogen. In fertility care, the temporary fall in oestrogen can increase signals that stimulate ovarian follicle development.
letrozole preparations and strengths
Tablet
Route: Oral
Strengths: 2.5 mg
How to take letrozole
Follow instructions from the prescribing team and the leaflet supplied with the product.
Swallow the tablet whole with water; do not crush or chew it.
It may be taken with or without food.
Do not stop treatment or take a treatment break without discussing this with the specialist team.
If tired, dizzy or affected by blurred vision, do not drive, cycle or operate machinery until fully recovered.
letrozole side effects
Common or expected effects
- Hot flushes and increased sweating
- Joint, muscle or bone pain
- Tiredness
- Nausea or other digestive symptoms
- Headache or dizziness
- Raised cholesterol or blood pressure
- Low mood
- Hair thinning or rash
- Vaginal bleeding
- Reduced bone density, osteoporosis or fractures
Get urgent medical advice
- Severe allergic reaction, including swelling or breathing difficulty
- Sudden chest pain or symptoms of a stroke
- Painful, swollen, warm or red limb suggesting a blood clot
- Yellow skin or eyes, suggesting liver injury
- Fever, chills, repeated mouth ulcers or sore throat suggesting infection or low white blood cells
- Significant tendon pain, swelling or possible rupture
- Severe blistering or peeling skin reaction
letrozole in pregnancy
Letrozole is contraindicated during pregnancy because it may harm fetal development. Ovarian function can occasionally return despite an apparently postmenopausal state, so contraception may need discussion. Specialists sometimes use letrozole off-label to induce ovulation, but it must not be taken during an established pregnancy.
letrozole while breastfeeding
Letrozole is contraindicated while breastfeeding. It is unknown whether letrozole or its metabolites enter human milk, and a risk to the infant cannot be excluded. Discuss alternatives with the specialist team.
letrozole interactions
Tell the prescriber or pharmacist about all prescribed, over-the-counter and complementary products.
Tamoxifen
May substantially reduce letrozole concentrations and diminish its action; concurrent use should be avoided unless specifically directed by a specialist.
Other anti-oestrogens
May oppose or diminish letrozole's action and should generally not be combined with it.
Oestrogen-containing treatments, including HRT
Can reduce letrozole's effect and should not usually be taken concurrently.
Common questions about letrozole
Answers are fully visible for fast scanning and source review.
Is letrozole chemotherapy?
No. It is endocrine therapy called an aromatase inhibitor; it lowers oestrogen rather than acting as conventional cytotoxic chemotherapy.
Is letrozole used for fertility treatment?
Fertility specialists may use it to induce ovulation, but this is a non-licensed use requiring specialist assessment and monitoring.
Why are bone scans used?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.