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Letrozole oral

Updated 2 Feb 2023 | Breast cancer


Oral formulations of letrozole.

Drugs List

  • FEMARA 2.5mg tablets
  • letrozole 2.5mg tablets
  • Therapeutic Indications


    Adjuvant therapy postmenop. women for hormone receptor+ early breast cancer
    Advanced breast cancer (post-menopausal) after anti-oestrogen failed
    Advanced hormone dependent breast cancer in post menopausal women
    Early invasive breast cancer in postmenop women prev treated with tamoxifen
    Hormone receptor +ve, HER2 -ve breast cancer in post menopausal women

    Adjuvant treatment of postmenopausal women with hormone receptor positive invasive early breast cancer.

    Extended adjuvant treatment of early invasive breast cancer in postmenopausal women, who have received prior standard adjuvant tamoxifen therapy (5 years).

    Advanced breast cancer in post-menopausal women after other anti-oestrogen therapy has failed.

    First-line treatment in post-menopausal women with hormone-dependent advanced breast cancer.

    Neo-adjuvant therapy in post-menopausal women with hormone receptor positive, HER-2 negative breast cancer where chemotherapy is not suitable and immediate surgery is not indicated.


    Whilst the doses stated below are those recommended by the manufacturer, local cancer network protocols for the relevant indication should be consulted.


    The recommended dose is 2.5mg once daily.

    Due to a lack of long term data, the optimal duration of therapy has not yet been established.

    Extended adjuvant setting: Continue letrozole for 5 years or until tumour relapse occurs, whichever comes first.

    Adjuvant setting: Continue letrozole for 5 years or until tumour relapse occurs, whichever comes first. A sequential treatment schedule may be considered (letrozole 2 years and tamoxifen 3 years).

    In metastatic or advanced disease: Treatment with letrozole should continue until tumour progression is evident.

    Neo-adjuvant setting: Treat with letrozole for 4 to 8 months for optimal tumour reduction. Discontinue if the response is inadequate.

    Additional Dosage Information

    Advise patient that if a dose is missed, it should be taken as soon as possible. However, if it is less than 3 hours until the next scheduled dose, the missed dose should be skipped and the normal dosing schedule resumed.


    Children under 18 years
    Premenopausal females
    Breast cancer in males

    Precautions and Warnings

    Glucose-galactose malabsorption syndrome
    Lactose intolerance
    Renal impairment - creatinine clearance below 10ml/minute
    Severe hepatic impairment - Child-Pugh score greater than or equal to 10

    Advise ability to drive/operate machinery may be affected by side effects
    Contains lactose
    Consult local policy on the safe use of oral anti-cancer drugs
    Define menopause biochemically if in doubt about hormonal status
    Monitor closely patient with Child-Pugh C hepatic impairment
    Patients at risk of osteoporosis should have bone density assessed
    Advise patient to rest affected limb if tendonitis occurs
    May cause loss of bone mineral density
    Treatment or prophylaxis of osteoporosis should be started as appropriate
    Female: Ensure adequate contraception during treatment

    In patients whose post-menopausal status seems unclear, LH, FSH and/or estradiol levels must be assessed before initiating treatment in order to establish menopausal status.

    Despite a clear post-menopausal status, there are reports of woman regaining ovarian function. Adequate contraception should be discussed where necessary.

    Letrozole is a potent oestrogen lowering agent and reductions in bone mineral density can be anticipated. During adjuvant treatment with letrozole, women with osteoporosis or at risk of osteoporosis and those at risk of bone fractures should have their bone mineral density formally assessed by bone densitometry at the commencement of treatment and at regular intervals thereafter. Treatment for osteoporosis should be initiated as appropriate and patients should be carefully monitored.

    Pregnancy and Lactation


    Letrozole is contraindicated during pregnancy.

    The manufacturer states that letrozole is contraindicated during pregnancy. Letrozole is thought to cause congenital malformations when administered during pregnancy. Briggs (2015) suggests this may be due to letrozole's inhibition of estrogen synthesis in all tissues.

    Animal studies have shown reproductive toxicity. An increased incidence of developmental abnormalities and foetal resorptions were observed, however it is not known whether this was an indirect consequence of inhibition of oestrogen biosynthesis, or a direct drug effect.


    Letrozole is contraindicated during breastfeeding.

    The manufacturer recommends that letrozole is contraindicated during breastfeeding.

    At the time of writing, there is no data on the transfer of letrozole or its metabolites into human breast milk.

    The molecular weight, low plasma protein binding and long terminal elimination half-life suggest it is likely that letrozole will be excreted into breast milk.

    LactMed (2017) states that some manufacturers recommend that breastfeeding is discontinued during treatment, and for 3 weeks after the last dose.

    Side Effects

    Abdominal pain
    Anaphylactic reaction
    Angina pectoris
    Arterial thrombosis
    Blurred vision
    Bone pain
    Breast pain
    Cardiac failure
    Carpal tunnel syndrome
    Cerebrovascular accident
    Dry mouth
    Dry mucous membranes
    Dry skin
    Endometrial hyperplasia
    Erythema multiforme
    Eye irritation
    Hot flushes
    Impaired memory
    Increased appetite
    Increased sweating
    Increased urinary frequency
    Increases in hepatic enzymes
    Myocardial infarction
    Myocardial ischaemia
    Night sweats
    Ovarian cysts
    Peripheral oedema
    Pulmonary embolism
    Taste disturbances
    Tendon inflammation
    Tendon rupture
    Thromboembolic disorders
    Toxic epidermal necrolysis
    Transient ischaemic attack
    Trigger finger
    Tumour pain
    Urinary retention
    Urinary tract infections
    Vaginal bleeding
    Vaginal discharge
    Vaginal dryness
    Weight gain
    Weight loss


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: March 2018

    Reference Sources

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.

    Summary of Product Characteristics: Femara 2.5 mg Tablets. Novartis Pharmaceuticals UK Ltd. Revised December 2019.

    Summary of Product Characteristics: Letrozole 2.5 mg Dr. Reddy's Laboratories UK Ltd. Revised October 2019.

    Summary of Product Characteristics: Letrozole 2.5 mg film-coated tablets. Teva UK Ltd. Revised October 2017.

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Letrozole Last revised: 10 October 2017
    Last accessed: 27 March 2018

    NICE Evidence Services Available at: Last accessed: 23 March 2018

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