Susan G Komen  
I've Been Diagnosed With Breast Cancer Someone I Know Was Diagnosed Share Your Story Join Us And Stay Informed Donate To End Breast Cancer
Home > Understanding Breast Cancer > Treatment > Tamoxifen





Hormone Therapy Video
Macromedia Flash


Fact Sheet


Breast Cancer 101 (Interactive Multimedia) - Tamoxifen
Macromedia Flash


Research Fast Facts: Breast Cancer Therapies
Fact Sheet

Tamoxifen (Nolvadex) has been used for over 40 years to treat breast cancers that are hormone-receptor positive. Hormone receptor-positive 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.  

Figure 5.9 

Illustration of tamoxifen 

Source: British Broadcasting Corporation

Tamoxifen as breast cancer treatment

Treatment with tamoxifen lowers the risk of [56]:

Tamoxifen is a pill taken every day for up to five years. The benefits from tamoxifen last long after you stop taking it.  

Findings from a large randomized clinical trial showed that taking tamoxifen for an additional five years (for a total of 10 years) further reduced the risk of breast cancer recurrence and death [60]. For this reason, there is increasing use of treatment with tamoxifen for more than five years, especially among premenopausal women who cannot take aromatase inhibitors. However, taking tamoxifen for a longer time means there is a continued risk of health effects, such as endometrial cancer [60]. For premenopausal women, tamoxifen may also impact fertility (learn more).  

Women should discuss the benefits and risks of taking tamoxifen for more than five years with their health care providers.

Tamoxifen and antidepressant use

Some types of antidepressants called selective serotonin reuptake inhibitors (SSRIs) can interfere with the metabolism of tamoxifen (how tamoxifen works in the body). Some SSRIs (such as fluoxetine (Prozac), buproprion (Wellbutrin), paroxetine (Paxil) and sertraline (Zoloft)) interfere with tamoxifen so much that they should be avoided while taking tamoxifen [51]. If you are taking an SSRI to treat depression or menopausal symptoms, talk to your health care provider about possible drug interactions and other treatment options.  

Learn about SSRI antidepressants for the treatment of menopausal symptoms.  

Tamoxifen as a risk-lowering drug

Among cancer-free women who have a high risk of developing breast cancer (including those with atypical hyperplasia or lobular carcinoma in situ) tamoxifen can be taken to lower risk [61].  

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    

Side effects of tamoxifen

The side effects of tamoxifen differ from those of other hormone therapies. Learn more about the side effects of tamoxifen  

 Komen Support Resources  



Importance of following your breast cancer treatment plan

Breast cancer treatment is most effective when all parts of the treatment plan are followed. So, it is important to follow your treatment plan (for medications and other therapies) prescribed by your health care provider in terms of:

  • Timing
  • Dose
  • Frequency

Completing tamoxifen treatment

Tamoxifen for breast cancer treatment may be prescribed for five to 10 years. The length of treatment coupled with side effects can make adherence to tamoxifen difficult. Although the menopausal symptoms related to tamoxifen can be hard to deal with, there are treatments that may ease these side effects. If you have side effects, talk to your health care provider about ways to treat them.

To get the most benefit out of your treatment, you need to take the full course of hormone therapy. Women who complete the full course have higher rates of survival [59].

If you have trouble remembering to take your tamoxifen, a daily pillbox or setting an alarm on your watch or phone may help [3]. 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.

Prescription drug assistance

Tamoxifen is off-patent and available in a generic form. Generics are cheaper 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 assistance from programs that help with drug costs or offer low-cost or free prescriptions.

Learn more about insurance plans and prescription drug assistance programs.  

Updated 03/28/14 


Hormone Therapies 

Side Effects of Tamoxifen  



Aromatase Inhibitors 


    Side Effects of Aromatase Inhibitors 



Ovarian Suppression (Therapies that Stop the Ovaries from Producing Hormones)



Emerging Areas in Chemotherapy, Hormone Therapy and Targeted Therapy


    Questions for Your Provider - Hormone Therapy