Updated contraception advice for tamoxifen

The recommended duration of contraception after finishing tamoxifen treatment has been extended from two months to nine months. This means women should continue their contraception and not become pregnant for at least nine months after tamoxifen therapy has ended.

Tamoxifen is a selective estrogen receptor modulator. It inhibits tumour growth by competing with estrogen for receptor sites in breast tissue and is indicated for:

• treatment of breast cancer
• primary reduction of breast cancer risk in women with a moderately increased or high risk

Pregnancy contraindication

Tamoxifen is contraindicated in pregnancy and the possibility of pregnancy should be excluded before treatment is started. Women of child-bearing potential should be advised to use barrier or other non-hormonal contraceptive methods if they are sexually active, both during treatment and for nine months after treatment has ended.

Women should be informed about the potential risks to the foetus, should they become pregnant while taking tamoxifen or within nine months of finishing treatment.

The Australian pregnancy category for tamoxifen remains unchanged - Category B3. A small number of reports of spontaneous abortions, birth defects and foetal deaths have occurred after women have taken tamoxifen, although no causal relationship has been established.

Why has the contraception duration been extended?

This change is based on US FDA guidance for genotoxic pharmaceuticals which recommends a minimum contraception period of six months plus five elimination half-lives after cessation of therapy.

Disclaimer

Medicines Safety Update is aimed at health professionals. It is intended to provide practical information to health professionals on medicine safety, including emerging safety issues. The information in Medicines Safety Update is necessarily general and is not intended to be a substitute for a health professional's judgment in each case, taking into account the individual circumstances of their patients. Reasonable care has been taken to ensure that the information is accurate and complete at the time of publication. The Australian Government gives no warranty that the information in this document is accurate or complete, and shall not be liable for any loss whatsoever due to negligence or otherwise arising from the use of or reliance on this document.

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