Tamoxifen (Nolvadex) has been used for over 40 years to treat breast cancers that are hormone-receptor positive. These breast cancers need the hormone estrogen (and/or progesterone) to grow. Figure 5.9 below shows how tamoxifen works. Tamoxifen attaches to the hormone receptor in the cancer cell, blocking estrogen from attaching to the receptor. This slows or stops the growth of the tumor by preventing the cancer cells from getting the hormones they need to grow. Unlike aromatase inhibitors, tamoxifen can be used to treat breast cancer in both premenopausal and postmenopausal women. Tamoxifen is also used to treat breast cancer in men. Learn more about breast cancer in men.
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Treatment with tamoxifen lowers the risk of :
Tamoxifen is a pill taken every day for 5-10 years. The benefits from tamoxifen last long after you stop taking it.
Findings from a large randomized clinical trial showed that taking tamoxifen for 10 years reduced the risk of breast cancer recurrence and death more than taking tamoxifen 5 years .
These findings have led to increased use of tamoxifen for more than 5 years, especially among premenopausal women who cannot take aromatase inhibitors.
Taking tamoxifen for a longer time means a continued risk of health effects, such as endometrial cancer . For premenopausal women, tamoxifen may also impact fertility (learn more).
Discuss the benefits and risks of taking tamoxifen for more than 5 years with your health care provider.
Learn about the importance of completing treatment with tamoxifen.
Some types of anti-depressants called selective serotonin reuptake inhibitors (SSRIs) can interfere with the metabolism of tamoxifen (how tamoxifen works in the body) . Whether these SSRI may impact the effectiveness of tamoxifen is under study.
Some SSRIs (such as fluoxetine (Prozac), buproprion (Wellbutrin), paroxetine (Paxil) and sertraline (Zoloft)) may interfere with tamoxifen. However, it is not known whether this might affect tamoxifen treatment for breast cancer.
If you are taking an SSRI to treat depression or menopausal symptoms, talk with your health care provider about possible drug interactions and other treatment options.
Learn about SSRI anti-depressants for the treatment of menopausal symptoms.
Among women who have a high risk of developing breast cancer (but have not been diagnosed) tamoxifen can be taken to lower risk .
Learn more about risk-lowering drugs and other options for women at high risk of breast cancer.
Learn more about tamoxifen on the National Institutes of Health's Medline Plus website.
The side effects of tamoxifen include menopausal symptoms such as hot flashes and vaginal dryness.
Learn more about the side effects of tamoxifen.
In addition to treating and lowering the risk of breast cancer, tamoxifen may have other health benefits. Tamoxifen may:
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Breast cancer treatment is most effective when all parts of the treatment plan are followed.
It is important to follow the treatment plan (for medications and other therapies) prescribed by your health care provider in terms of:
Tamoxifen for breast cancer treatment is prescribed for 5-10 years. The length of treatment coupled with side effects can make it tough to complete tamoxifen therapy.
Although the menopausal symptoms from tamoxifen can be hard to deal with, there are things you can do that may ease these side effects. Talk with your health care provider about ways to treat them.
To get the most benefit from hormone therapy, you need to take the full course of treatment. Women who complete the full course have better survival than those who do not .
If you have trouble remembering to take your tamoxifen, a pillbox or setting an alarm on your watch or phone (you may be able to download an app) may help . However, you do not need to panic if you miss a day or two.
Learn more about the importance of following your breast cancer treatment plan.
Tamoxifen is off-patent and available in a generic form. Generics cost less than name brand drugs, but are just as effective.
Medicare and many insurance providers 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 programs that help with drug costs or offer low-cost or free prescriptions.
Learn more about insurance plans and prescription drug assistance programs.
Susan G. Komen’s position on fairness in breast cancer medication coverage
Medications taken by mouth (oral) are usually covered under a health insurance plan’s prescription drug benefit rather than the plan’s medical benefit. As a result, people often find themselves facing high out-of-pocket costs when filling their prescriptions (sometimes costing thousands of dollars per month). High prescription drug costs are a barrier to care. High costs can prevent people from getting the medications prescribed by their health care provider.
Komen supports efforts at the state and federal levels that require insurers to provide coverage for oral breast cancer medications at a rate no less favorable than what they provide for IV medications to ensure patients have access to affordable, appropriate treatment for their cancer.
Facts for Life: Tamoxifen
Hormone Therapy Video
Breast Cancer 101 - Aromatase Inhibitors
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