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.
What to report? You don't need to be certain, just suspicious!
The TGA encourages the reporting of all suspected adverse reactions to medicines, including vaccines, over-the-counter medicines, herbal, traditional or alternative remedies.
We particularly request reports of:
- all suspected reactions to new medicines (look for the Black Triangle in PI and CMI documents - this symbol identifies medicines that are new or being used differently)
- all suspected medicines interactions
- suspected reactions causing death, admission to hospital or prolongation of hospitalisation, increased investigations or treatment, or birth defects.
Reports may be submitted:
- online at www.tga.gov.au
- by fax to 02 6232 8392
- by email to ADR.Reports@tga.gov.au
For more information about reporting, visit www.tga.gov.au or contact the TGA's Pharmacovigilance and Special Access Branch ADR.Reports@tga.gov.au.
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.
© Commonwealth of Australia 2021
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For correspondence or further information about Medicines Safety Update, contact the TGA's Pharmacovigilance and Special Access Branch at ADR.Reports@tga.gov.au.
Medicines Safety Update is written by staff from the Pharmacovigilance and Special Access Branch.
Acting Editor: Dr Catherine Brogan
Deputy Editor: Mr Michael Pittman
Contributor: Dr Fiona Mackinnon and Mr David Phuong
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