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Tamoxifen - Hormone Therapy to Prevent Breast Cancer Recurrence


Updated June 26, 2014

Tamoxifen tablets

Tamoxifen tablets

Karl D. Stephan


Tamoxifen is an antiestrogen (estrogen suppressor) medication, taken as a 10 or 20 mg tablet. Tamoxifen is not a steroid. This medication helps lower the risk that breast cancer will return and improves survival rates.

Drug type:

Tamoxifen is a selective estrogen receptor modulator (SERM). Raloxifene (Evista) is another SERM given to treat breast cancer.


Tamoxifen is given to female and male breast cancer patients to suppress estrogen and prevent the return of breast cancer. It may be given during chemotherapy and radiation, or as a follow-up treatment about two to five years after an initial course of treatment is completed. Tamoxifen can also be given as a preventive medication to patients who are at high risk of developing breast cancer.
Tamoxifen is effective on estrogen-receptor positive breast cancer.


ta MOKS i fen

Also known as:

tamoxifen citrate, Nolvadex, Soltamox, Tamofen

Available as:

brand name and generic tablets

Common Misspellings:

tamoxifan, tamoxifin, tomoxafin


Do not take this drug with grapefruit juice because it amplifies menopause-like symptoms, such as hot flashes. Use contraception during treatment, and for two months after ceasing use of this drug. Do not take tamoxifen if you are pregnant. Do not take with warfarin (a blood thinner) or anastrozole.

How Tamoxifen Works:

Some breast cancers are fueled by estrogen. Tamoxifen works by blocking estrogen receptors in breast tissue, which helps prevent cancer from growing. It can be given after initial treatments (chemotherapy, radiation) have been completed to prevent the original breast cancer from returning and help prevent new tumors from forming.

Common Side Effects:

  • Difficulty breastfeeding
  • Menopausal symptoms (hot flashes, vaginal dryness)
  • Irregular menstrual cycle
  • Osteoporosis (bone thinning)
  • Headache
  • Fatigue
  • Low libido

Rare or low-risk side effects (less than one per cent chance)

  • Endometrial cancer
  • Uterine sarcoma
  • Pulmonary embolism (blocked artery in a lung)
  • Deep vein thrombosis (blood clot)
  • Stroke
  • Cataracts
  • Damage to fetus (birth defects)
  • Memory loss

Is Tamoxifen Worth the Tradeoffs?

Weighing risks and benefits of taking tamoxifen may seem tricky, but most doctors agree that the benefits outweigh the risks. Although tamoxifen blocks estrogen in the breast, it acts like estrogen in your other tissues. This may lower bad cholesterol and protect bones from osteoporosis.

National Cancer Institute. Tamoxifen: Questions and Answers. Last Updated: May 1, 2002. Tamoxifen: Questions and Answers
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