Family doctor



TAMOXIFEN - a patient's guide


This drug is used in the treatment of breast cancer and endometrial cancer, but it can have significant side effects. This article profiles these and how the medicine works.

Brand Names:

  • Genox
  • Nolvadex
  • Tamofen


Tamoxifen (tam-ox-i-fen) is a medicine that is used for the treatment of breast cancer and endometrial (en-do-me-tre-al) cancer. In breast cancer tamoxifen stops oestrogen (a female hormone) from working in the breast tissue, this is called an "anti-oestrogen effect", which reduces the stimulation of breast cancer growth from the oestrogen in the body. Tamoxifen is not a steroid.

Sometimes tamoxifen is used alone, other times it is used along with other medicines.

Tamoxifen also has a couple of other useful effects in that it lowers cholesterol and helps keep up the bone density. It is not prescribed for these effects, but it is nice to know that there are other benefits of taking tamoxifen.

While tamoxifen has been undergoing trials for prevention of breast cancer, it is not currently recommended for this.


The usual dose is 20 mg or 40 mg of tamoxifen per day.


Tamoxifen must not be taken during pregnancy, and therefore pregnancy should be avoided while taking tamoxifen and for 2 months after finishing taking tamoxifen (as it takes a while to leave the body). Hormonal contraception ("the pill") is not advisable with tamoxifen.

Tamoxifen should not be used during breastfeeding.

Patients with bony metastases may be prone to hypercalcaemia (high calcium in the blood).

Side effects:

The side effects of tamoxifen are an improvement on some older medicines for breast cancer, and the benefits of treatment are far greater than the risks of treatment.

Some women who have not yet reached menopause may miss periods while on tamoxifen for breast cancer. Hot flushes, upset stomach, and vomiting are reasonably common.

There is an increased possibility of problems of the endometrium (lining of the womb) including a small risk of endometrial cancer, therefore women must report to their doctor without delay if any of the following symptoms occur:

  • Unusual bleeding from the vagina (e.g. bleeding between periods, heavier periods than usual or bleeding after menopause)
  • Changes in vaginal discharge
  • Pain or pressure below the stomach

These symptoms are warnings that the doctor needs to investigate. Even without these symptoms an annual pelvic examination may be useful. Remember that the benefits of treatment are far greater than the risks of treatment.

Side effects can happen on the eye, and therefore if you have blurred vision lasting more than 2 weeks or a change in colour vision, talk immediately to your doctor.

There may be increased risk of thromboembolic (blockage of a blood vessel) problems such as deep vein thrombosis (DVT); this may be further increased if there is use of cytotoxic medicines also.

Other possible side effects include:

  • Vaginal discharge
  • Pruritis vulvae (itching in the genital area)
  • Headache
  • Lightheadedness
  • Skin rashes
  • Cystic ovarian swellings
  • Changes to blood counts and liver enzyme levels
  • Tumour flare-up


Anticoagulants may have increased effect when used with tamoxifen.

Use of tamoxifen with cytotoxic medicines may increase the risk of thromboembolic (blood vessel blockage) problems.

Patient information:

  • Follow the instructions on the label of the medicine or as directed by your doctor.
  • Talk to your doctor without delay if you have changes in vaginal bleeding, vaginal discharge, or pain or pressure below the stomach.
  • Talk to your doctor promptly if you have a change in colour vision or blurred vision for two weeks.
  • It is important not to become pregnant while using this medicine.
  • Discuss any questions or concerns you may have about this medicine with your doctor.

See also:

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