How does it work?

This medicine contains the active ingredient tamoxifen citrate, which is a type of medicine known as an 'anti-oestrogen'. It is mainly used to treat women with breast cancers that respond to the female sex hormone, oestrogen. Most breast cancers are sensitive to oestrogen, and their growth is increased in the presence of this hormone. Oestrogen binds to oestrogen receptors on the breast cancer cells and causes changes within the cells that result in faster growth of the cancer. Tamoxifen works by blocking these oestrogen receptors, thereby blocking the effect of oestrogen on the cancer. This reduces the size of oestrogen-sensitive tumours. Tamoxifen is also used in the treatment of female infertility that is caused by problems with ovulation. Again, it acts by blocking oestrogen receptors, this time in a part of the brain called the hypothalamus. The effect of this is an increase in the levels of the hormones that control the development and release of an egg. These hormones are released from the pituitary gland and are known as follicle stimulating hormone (FSH) and luteinising hormone (LH). FSH stimulates the ovaries and LH causes the release of an egg from the ovaries (ovulation). In the normal menstrual cycle, oestrogen acts on receptors in the hypothalamus after ovulation. This causes the pituitary gland to stop releasing FSH and LH. As tamoxifen blocks the oestrogen receptors in the hypothalamus, it prevents this action of oestrogen. FSH and LH levels therefore increase, which increases the chances of egg development and ovulation.

What is it used for?

Breast cancer

Infertility in women caused by failure of ovulation

Warning!

As this medicine may potentially cause harm to a developing baby, it should not be used during pregnancy. Pre-menopausal women should use a non-hormonal method of contraception to prevent pregnancy both during, and for two months following, treatment with this medicine.

Your doctor may want you to stop taking this medicine prior to any planned surgery or period of prolonged immobility. Discuss this with your doctor.

Tamoxifen is associated with a small increase in the risk of endometrial cancer. The benefits of taking tamoxifen to treat breast cancer outweigh this risk, however, to minimise the risk you should consult your doctor if you experience any abnormal gynaecological symptoms during or after treatment, so that they can be investigated. Symptoms to report include vaginal bleeding, menstrual irregularities, vaginal discharge, or symptoms such as pelvic pain or pressure. Consult your doctor for further information.

Tamoxifen is associated with an increased risk of abnormal blood clots in the blood vessels (deep vein thrombosis or pulmonary embolism), particularly during periods of immobilisation and following surgery. The benefits of taking tamoxifen to treat breast cancer outweigh this risk, however you should consult your doctor immediately if you experience any of the following symptoms during treatment: stabbing pains and/or unusual swelling in one leg, pain on breathing or coughing, sudden breathlessness or sudden severe chest pain. Consult your doctor for further information.

Use with caution in

Breast cancer patients with a personal or family history of abnormal blood clots in the veins

Severe obesity

Smokers

Not to be used in

Breastfeeding

Infertility patients with a personal or family history, or genetic risk, of abnormal blood clots in the veins with no known cause

Pregnancy

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy. If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and Breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

This medicine must not be used during pregnancy as it may potentially cause harm to a developing baby. Pre-menopausal women should use a non-hormonal method of contraception to prevent pregnancy both during, and for two months following, treatment with this medicine.

As there is no safety information available, the manufacturer does not recommend the use of this medicine when breastfeeding. Alternatively, if this medicine must be used, the mother should not breastfeed. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Headache

Blood disorders

Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain

Visual disturbances

Severe swelling of lips, face or tongue (angioedema)

The presence of tissue similar to the lining of the uterus at other sites in the pelvis (endometriosis)

Severe blistering skin reaction affecting the tissues of the eyes, mouth, throat and genitals.(Stevens-Johnson Syndrome)

Suppression of menstrual periods

Stimulation of tumour growth

Hair loss (alopecia)

Liver disorders

Itching of the external female genitalia (pruritus vulva)

Cancerous changes in the endometrium (lining of the womb).

Increased risk of abnormal blood clots within the blood vessels (thromboembolic disorders)

Fibroids in the womb (uterus)

Vaginal bleeding or discharge

Hot flushes

The side effects listed above may not include all of the side effects reported by the drug's manufacturer. For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

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