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Breast Cancer Health Center

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Breast Cancer and Hormone Therapy

Breast Cancer and Tamoxifen continued...

Some people should not use tamoxifen:

  • Pregnant women
  • Women planning to get pregnant
  • Men or women who’ve had blood clots or a stroke

Talk to your doctor to see if tamoxifen is right for you.

For women, the side effects of tamoxifen are similar to some of the symptoms of menopause. Two of the most common ones are hot flashes and vaginal discharge. Other problems for women may include:

  • Vaginal dryness or itching
  • Irregular periods
  • Headache
  • Nausea and vomiting
  • Skin rash
  • Fatigue
  • Water retention and weight gain

The side effects may be similar to menopause, but tamoxifen doesn’t trigger menopause.

For men, tamoxifen can cause:

  • Headache
  • Nausea and vomiting
  • Skin rash
  • Sexual side effects like erectile dysfunction or a lower sex drive

Are There Risks to Taking Tamoxifen?

Yes. The risks include:

  • Fertility. Tamoxifen can increase a woman’s fertility for a short time. But it might be harmful to a growing baby, so it’s important to use some form of barrier birth control while you are taking it, like condoms or a diaphragm. Don’t use birth control pills since they may change how the drug works and affect the breast cancer. Tell your doctor right away if you think you’ve become pregnant while you’re taking tamoxifen.
  • Blood clots. Women who take tamoxifen may have a slightly higher risk of blood clots in their lungs or large veins. It’s an even bigger risk for smokers.
  • Stroke.
  • Uterine cancer or sarcoma. The drug may increase a woman's risk of these diseases. But this risk is very small, and it may be outweighed by the benefits of tamoxifen for breast cancer treatment. Talk to your doctor to know for sure.
  • Cataracts. Tamoxifen seems to put some women at increased risk for this condition that clouds the lens inside the eye. People have also reported eye problems such as corneal scarring or retinal changes.
  • Medications. Tamoxifen may affect how other drugs work in your body.

Tamoxifen and Breast Cancer Prevention

In 1998, the National Cancer Institute did a large study to find out whether tamoxifen lowered cases of breast cancer in healthy women who were known to be at high risk for the disease. The results of the trial showed a 50% reduction in breast cancer in the women who took the drug.

Studies have also shown that tamoxifen reduces the risk of breast cancer in women who have had the earliest form of the disease, ductal carcinoma in situ (DCIS).

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