- Drugs List
- Therapeutic Indications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
Tablet formulations of tamoxifen.
Breast cancer (women at moderate to high risk): Primary prevention
Carcinoma of breast
Infertility - female - anovulatory
Treatment of breast cancer.
Prevention of breast cancer in women at moderate to high risk.
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.
The recommended daily dose is 20mg.
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.
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.
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
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 ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
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 https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1
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.
Abnormal vaginal bleeding
Alterations in hepatic enzymes
Cutaneous lupus erythematosus
Deep vein thrombosis (DVT)
Hepatic disorders (fatty changes)
Porphyria cutanea tarda
Radiation recall dermatitis
Reduced platelet count
Reversible cystic ovarian swellings
Risk of endometrial carcinoma
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 ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Last Full Review Date: October 2018
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: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
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: www.nice.org.uk Last accessed: 24 October 2018
The Welsh Medicines Information Centre (WMIC) Porphyria Information Service.
Available at: https://www.wmic.wales.nhs.uk/porphyria_info.php
Last revised: 03 May 2018
Last accessed: 24 October 2018
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Medscape UK | Univadis prescription drug monographs & interactions are based on FDB Multilex Content
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