What is Tamoxifen?

Tamoxifen is a hormone therapy used to treat breast cancers that are hormone receptor positive (HR+). The brand names of tamoxifen are Nolvadex® (tamoxifen) and SoltamoxTM (tamoxifen). (SoltamoxTM is an oral liquid form.) Tamoxifen has been available in a generic form since 2006.1

Tamoxifen may be used as an adjuvant treatment (after surgery) for early stage breast cancer in women. It may also be used to reduce the risk of developing breast cancer in women who are at high risk of developing the disease, such as those with a strong family history of breast cancer. Tamoxifen may also be used in those who have had ductal carcinoma in situ (DCIS) to help decrease the risk of a more invasive form of breast cancer. Tamoxifen may potentially be used for men and women when the breast cancer has metastasized (spread beyond the breast to other areas of the body).2

What is tamoxifen?

Tamoxifen is considered an antiestrogen medication.

How does tamoxifen work?

Many breast cancers have estrogen receptors on the surface of their cells. Estrogen can connect to these receptors and stimulate the growth of these breast cancers. Tamoxifen blocks estrogen and may stop or slow the growth of cancerous cells.2

What are some of the possible side effects of tamoxifen?

Tamoxifen may cause serious side effects. In women who use tamoxifen to reduce the risk of developing breast cancer, some serious and life-threatening side effects have occurred, including uterine cancer, stroke, and pulmonary embolism (a blood clot in the lungs).2,3

Tamoxifen may increase the risk of developing blood clots and cataracts.2,3

Tamoxifen may increase the risk of developing other cancers, such as liver cancer.2

The most common side effects experienced by patients taking tamoxifen include3:

  • Hot flashes
  • Vaginal discharge
  • Changes to the menstrual cycle, which may include a discontinuation of menstruation

Other potential side effects of tamoxifen include2:

  • Increased bone or tumor pain
  • Nausea
  • Fatigue
  • Dizziness
  • Depression
  • Headache
  • Hair thinning
  • Weight loss
  • Stomach cramps
  • Constipation

Things to know about tamoxifen

Before starting treatment with tamoxifen, patients should talk to their doctor about all medications (prescription and over-the-counter), vitamins, and herbal supplements they are taking. Some medications or supplements may interfere with each other and may cause side effects.2

Before beginning tamoxifen, patients should discuss with their doctor all their health conditions, including2:

  • High cholesterol
  • History of blood clots in the lungs or legs
  • History of stroke or heart attack
  • High blood pressure
  • Diabetes
  • If patients are pregnant, or planning to become pregnant
  • If patients are breastfeeding, or planning to breastfeed

Tamoxifen may cause harm to an unborn baby and should not be used by women who are pregnant. Women who can become pregnant should use effective contraception while taking tamoxifen and for at least two months after the last dose of tamoxifen. Patients should discuss effective contraception methods with their doctor.3

It is not known if tamoxifen can pass into breastmilk. Women should not breastfeed during tamoxifen treatment.3

Dosing information

Tamoxifen comes in a tablet and oral liquid form. The dosage of 20-40 mg/day should be taken by mouth once or twice daily with food. Tamoxifen should be taken at about the same time each day. For adjuvant treatment, tamoxifen is taken for at least five years. For breast cancer prevention, tamoxifen is usually taken for five years.2

For more information, read the full prescribing information for Soltamox or the full prescribing information for Nolvadex.

Patients should take their medication as prescribed by their doctor. Patients should talk to their doctor if they have any questions, or if they have questions regarding their tamoxifen regimen.

View References
  1. Zeidan B, Anderson K, Peiris L, Rainsbury D, Laws S. The impact of tamoxifen brand switch on side effects and patient compliance in hormone receptor positive breast cancer patients. Breast. 2016 Oct;29:62-7. doi: 10.1016/j.breast.2016.07.001. Epub 2016 Jul 16. Abstract.
  2. Tamoxifen. MedlinePlus, U.S. National Library of Medicine. Available at https://medlineplus.gov/druginfo/meds/a682414.html. Accessed 9/20/18.
  3. http://soltamox.com/wp-content/uploads/2016/07/Soltamox-FDA-Approved-Package-Insert.pdf.