The Who, What, Where, When and Sometimes, Why.

Risk-Lowering Drugs

Tamoxifen and raloxifene are the only FDA-approved drugs for breast cancer risk reduction in women at higher than average risk.

You may also hear the term “chemoprevention” to describe these drugs, but they aren’t chemotherapy drugs.

Tamoxifen is used to treat and prevent breast cancer. Raloxifene is only used to prevent breast cancer.

Both tamoxifen and raloxifene are pills.

For a summary of research studies on tamoxifen and raloxifene and breast cancer prevention, visit the Breast Cancer Research Studies section.

Tamoxifen and raloxifene

Breast cancer risk

Both tamoxifen and raloxifene can lower the risk of [235]:

  • Invasive breast cancer
  • Non-invasive breast cancer, such as ductal carcinoma in situ (DCIS)

Tamoxifen and raloxifene only reduce the risk of estrogen receptor-positive breast cancers. Neither drug reduces the risk of estrogen receptor-negative cancers [235].

Tamoxifen is more effective than raloxifene in lowering breast cancer risk [235]. Tamoxifen lowers risk by about 50 percent in women at high risk [235]. Raloxifene lowers risk by about 38 percent in women at high risk [235]. However, raloxifene has fewer harmful side effects than tamoxifen (see table below) [235]. This makes raloxifene a better choice for some women.

Side effects

Both tamoxifen and raloxifene have some long-term side effects (see table below) and may not be right for all women at higher than average risk. For example, tamoxifen increases the risk of cataracts and cancer of the uterus [235].

Talk with your health care provider about the possible harms and benefits of these drugs.

Learn more about the side effects of tamoxifen.

Learn more about talking with your health care provider.

Tamoxifen versus raloxifene
Who can take the drug?
  • Premenopausal women ages 35 and older
  • Postmenopausal women


  • Postmenopausal women only


How is the drug taken?
  • A pill taken once a day for 5 years


  • A pill taken once a day for 5 years


What are common short-term side effects?
  • Hot flashes
  • Irregular periods or spotting (uterine bleeding)
  • Leg cramps
  • Vaginal discharge
  • Vaginal dryness or itching

Other side effects are less common.

  • Hot flashes
  • Leg cramps


What are the possible health risks?
  • Blood clots in the large veins (deep venous thrombosis)
  • Blood clots in the lungs (pulmonary emboli)
  • Cancer of the uterus or endometrium (the lining of the uterus)
  • Cataracts
  • Stroke

These effects occur mainly in older postmenopausal women.

  • Blood clots in the large veins (deep venous thrombosis)
  • Blood clots in the lungs (pulmonary emboli)
  • Stroke

These effects occur mainly in older postmenopausal women.

What about use in breast cancer treatment?Effective in the treatment of hormone receptor-positive breast cancerNot effective for breast cancer treatment
Adapted from selected sources [235,357-362].



Komen Perspectives

Read our perspective on risk-lowering drugs.*


Some types of anti-depressants called selective serotonin reuptake inhibitors (SSRIs) can interfere with how tamoxifen works in the body. It’s unlikely SSRIs impact the effectiveness of tamoxifen though [363-364].

If you’re taking an SSRI to treat depression or menopausal symptoms (such as hot flashes), talk with your health care provider about possible drug interactions.

Researchers are studying the benefit of tamoxifen for women who have a BRCA1 or BRCA2 inherited gene mutation and choose not to have prophylactic mastectomy.

Tamoxifen may be better at preventing breast cancer in women with a BRCA2 gene mutation than in women with BRCA1 gene mutations [365-366]. Tamoxifen only reduces the risk of estrogen receptor-positive (ER-positive) cancers [235]. BRCA2-related tumors are more likely than BRCA1-related tumors to be ER-positive [367].

Most of what we know about the potential benefits and harms of tamoxifen come from data on white women. There are few data about women of other ethnicities.

However, some older studies show Black women are more likely than white women to suffer from some of the harmful health effects of tamoxifen [368-369].

Aromatase inhibitors are hormone therapy drugs used to treat estrogen receptor-positive breast cancer in postmenopausal women.

Exemestane (Aromasin) and anastrozole (Arimidex)

Findings from randomized controlled trials of postmenopausal women at high risk have shown the aromatase inhibitors exemestane and anastrozole may lower the risk of breast cancer by about half [266-267].

Unlike tamoxifen and raloxifene, exemestane and anastrozole don’t appear to increase the risk of blood clots [266-267]. However, they can cause menopausal symptoms, a loss of bone density and other side effects [266-267,370-373].

The American Society for Clinical Oncology (ASCO), the National Comprehensive Cancer Network (NCCN) and the U.S. Preventive Services Task Force list exemestane and anastrozole as risk-lowering drug options for postmenopausal women at high risk of breast cancer. 

However, exemestane and anastrozole don’t have FDA-approval for use in the risk reduction setting. They are only FDA-approved for use in breast cancer treatment.

Learn about aromatase inhibitors (including exemestane and anastrozole) and breast cancer treatment.

Learn more about the side effects of aromatase inhibitors.

Other aromatase inhibitors

The aromatase inhibitor drug letrozole (Femara) is under study to see whether it may lower risk in postmenopausal women at high risk of breast cancer.

Learn about aromatase inhibitors and breast cancer treatment.

Other drugs currently used to treat breast cancer are under study for use in risk reduction and new risk-lowering drugs are being developed.

Learn more about emerging areas in breast cancer risk reduction.

If you’re at higher than average risk of breast cancer and considering joining a clinical trial of risk-lowering drugs, discuss the potential risks and benefits with your health care provider.

Susan G. Komen® Breast Care Helpline
If you or a loved one needs information or resources about clinical trials, call our Breast Care Helpline at 1-877 GO KOMEN (1-877- 465- 6636) or email in collaboration with Susan G. Komen® offers a custom matching service to help clinical trials on risk reduction.

Learn more about clinical trials

Tamoxifen and raloxifene are generic drugs. Generic drugs cost less than the name brands, but are just as effective.

Medicare and many insurance companies offer prescription drug plans. One may already be included in your policy. Or, you may be able to buy an extra plan for prescriptions.

You may also qualify for assistance from programs that help with drug costs or offer low-cost or free prescriptions.

The Affordable Care Act requires insurance plans (started on or after September 24, 2014) to cover the cost (with no co-payments) of tamoxifen and raloxifene for women at high risk of breast cancer. Learn more about this coverage.

Learn more about insurance plans, prescription drug assistance programs and other financial assistance resources.



  • If you or a loved one needs more information about breast health or breast cancer, call the Komen Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636). All calls are answered by a trained specialist or oncology social worker in English and Spanish, Monday through Friday from 9:00 a.m. to 10:00 p.m. ET. You can also email the helpline at
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  • Our fact sheets, booklets and other education materials offer additional information.

*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date.

Updated 02/26/21