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Tablet formulations of tamoxifen.

Drugs List

  • tamoxifen 10mg tablets
  • tamoxifen 20mg tablets
  • tamoxifen 40mg tablets
  • Therapeutic Indications


    Breast cancer (women at moderate to high risk): Primary prevention
    Carcinoma of breast
    Infertility - female - anovulatory

    Treatment of breast cancer.
    Anovulatory infertility.
    Prevention of breast cancer in women at moderate to high risk.

    Unlicensed Uses


    Prevention of gynaecomastia in men undergoing long-term bicalutamide treatment, if radiotherapy unsuccessful.


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


    Breast cancer
    The recommended daily dose is 20mg.

    Anovulatory infertility
    Regular menstruation with anovular cycle
    Recommended starting dose is 20mg daily on days 2 to 5 of the menstrual cycle.
    If treatment has been unsuccessful, increase dosage to 40mg in subsequent menstrual periods. Dosage may further be increased to 80mg in subsequent menstrual periods as necessary.

    Irregular menstruation
    Recommended starting dose is 20mg, beginning on any day
    If treatment has been unsuccessful, increase dosage to 40mg in subsequent treatment cycles, beginning a minimum of 45 days later. Dosage may further be increased to 80mg in subsequent treatment cycles as necessary.
    If treatment has been successful (patient responds with menstruation), the next course of treatment is commenced on the second day of the cycle.

    Prevention of breast cancer in women at moderate to high risk
    The recommended dose is 20mg daily, taken for 5 years.

    Gynaecomastia (unlicensed)
    20mg once weekly.

    Additional Dosage Information

    Dose reductions (to no less than the recommended starting dose) may be used to help manage severe side effects.


    Children under 18 years
    Family history of idiopathic venous thromboembolism - if for infertility
    History of deep vein thrombosis- if used for prevention of breast cancer
    History of pulmonary embolism- if used for prevention of breast cancer
    History of venous thromboembolism - if used in infertility treatment

    Precautions and Warnings

    Family history of venous thromboembolism
    Females of childbearing potential
    Predisposition to venous thromboembolism
    Glucose-galactose malabsorption syndrome
    History of thromboembolic disorder
    Lactose intolerance

    Advise patient that dizziness/fatigue may initially affect ability to drive
    Consider use of anticoagulant prophylaxis if at risk of thromboembolism
    Not all available brands are licensed for all indications
    Not all available strengths are licensed for all indications
    Treatment to be initiated by specialist
    Some formulations contain lactose
    Consult local policy on the safe use of oral anti-cancer drugs
    Staff: Not to be handled by pregnant staff
    Exclude pregnancy prior to initiation of treatment
    Investigate if abnormal vaginal bleeding, pain or discharge occurs
    Advise patient of thromboembolic symptoms and to report them if they occur
    Increased risk of venous thromboembolism
    May cause loss of bone mineral density
    Menstruation is suppressed in some pre-menopausal women during treatment
    Infertility:Discontinue 6 weeks before operations and during immobilisation
    Suspend if venous thromboembolism develops
    Advise patient not to take St John's wort concurrently
    Female: Non-hormonal contraception required for 2 months after treatment
    Advise patients risk of endometrial cancer and to report relevant symptoms

    An increased incidence of endometrial changes (including hyperplasia, polyps, cancer and uterine sarcoma) have been reported in association with tamoxifen use. Any patient who reports abnormal gynaecological symptoms (such as vaginal bleeding, menstrual irregularities, vaginal discharge and pelvic pain or pressure) should be promptly investigated.

    Patients with bony metastases are at an increased risk of hypercalcaemia.

    A 2 to 3 fold increase in the risk of developing venous thromboembolism has been shown in healthy women receiving tamoxifen.

    Due to the risk of thrombosis, patients being treated for infertility who are having surgery and subsequent immobility should stop taking tamoxifen at least 6 weeks before surgery. Patients may restart tamoxifen when fully mobile. Breast cancer patients undergoing surgery and subsequent immobility should only stop tamoxifen if the risk of thrombosis outweighs the risk associated with interrupting treatment. All patients should receive appropriate prophylactic measures to prevent thrombosis.

    A personal and family history of venous thromboembolism should be determined in breast cancer patients. Screen patients showing prothrombotic risk factors for thrombophilic factors; patients who test positive should be counselled on the risk of thromobosis.

    Discontinue tamoxifen immediately if patient presents with venous thromboembolism, and initiate appropriate treatment. Treatment for infertility should not be restarted unless there is a compelling alternative reason for the thrombosis. Treatment for breast cancer should only be restarted after additional risk assessment.

    Pregnancy and Lactation


    Tamoxifen is contraindicated in pregnancy.

    The manufacturers contraindicate the use of tamoxifen during pregnancy, citing a small number of reports of spontaneous abortions, birth defects and foetal deaths.

    Animal studies showed no teratogenic potential, but intrauterine growth restriction, abortions and premature delivery have been noted in some species.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Tamoxifen is contraindicated in breastfeeding.

    It is not known if tamoxifen is excreted in human milk. The manufacturers contraindicate tamifoxen's use in breastfeeding.

    LactMed states that tamoxifen can inhibit lactation, and should be avoided in nursing mothers.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at


    Advise patient risk of endometrial cancer and to report relevant symptoms

    Advise patient of thromboembolic symptoms, including calf pain or breathlessness, and to report them if they occur.

    Advise patient receiving, or having previously received, tamoxifen to report immediately any abnormal gynaecological symptoms such as menstrual irregularities, vaginal discharge or bleeding, pelvic pain or pressure suggestive of endometrial changes.

    Advise breast cancer patients to use barrier or other non-hormonal methods of contraception during treatment and for 2 months thereafter and inform them of the possible risks to the foetus should they become pregnant during treatment.

    Advise patient that dizziness and fatigue may initially affect ability to drive.

    Advise patient not to take St John's wort concurrently.

    Side Effects

    Abnormal vaginal bleeding
    Alterations in hepatic enzymes
    Bullous pemphigoid
    Corneal changes
    Cutaneous lupus erythematosus
    Cutaneous vasculitis
    Deep vein thrombosis (DVT)
    Dry skin
    Endometrial hyperplasia
    Endometrial polyps
    Erythema multiforme
    Fluid retention
    Gastro-intestinal disturbances
    Hepatic disorders (fatty changes)
    Hepatic failure
    Hepatic necrosis
    Hot flushes
    Hypersensitivity reactions
    Interstitial pneumonitis
    Leg cramps
    Menstrual disturbances
    Optic neuritis
    Optic neuropathy
    Porphyria cutanea tarda
    Pruritus vulvae
    Pulmonary embolism
    Radiation recall dermatitis
    Reduced platelet count
    Reversible cystic ovarian swellings
    Risk of endometrial carcinoma
    Stevens-Johnson syndrome
    Tumour flare
    Uterine fibroids
    Uterine sarcoma
    Vaginal discharge
    Visual disturbances
    Weight gain


    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: October 2018

    Reference Sources

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Tamoxifen Last revised: 10 March 2015
    Last accessed: 24 October 2018

    Summary of Product Characteristics: Tamoxifen Tablets. Generics UK. Revised March 2011.
    Summary of Product Characteristics: Tamoxifen Tablets. Teva. Revised March 2013.
    Summary of Product Characteristics: Tamoxifen Tablets. Wockhardt 10mg film-coated tablets UK Ltd. Revised August 2018
    Summary of Product Characteristics: Tamoxifen Tablets. Wockhardt 20mg film-coated tablets UK Ltd. Revised August 2018
    Summary of Product Characteristics: Tamoxifen Tablets. Wockhardt 40mg film-coated tablets UK Ltd. Revised May 2018

    NICE Evidence Services Available at: Last accessed: 24 October 2018

    The Welsh Medicines Information Centre (WMIC) Porphyria Information Service.
    Available at:
    Last revised: 03 May 2018
    Last accessed: 24 October 2018

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