Tamoxifen: What to Expect, Side Effects, and More
Tamoxifen (brand names: Nolvadex, Soltamox) is a medicine that blocks the effects of the hormone estrogen (called a selective estrogen receptor modulator, or SERM). Tamoxifen is a first choice among doctors for treating women who have not yet gone through menopause. The medicine can also be prescribed to women who have gone through menopause and to men.
You may be prescribed tamoxifen if:
You were diagnosed with early-stage, hormone receptor-positive breast cancer and have completed surgery and radiation.
You were diagnosed with hormone receptor-positive DCIS (ductal carcinoma in situ) and have completed surgery and radiation.
You were diagnosed with advanced-stage, hormone receptor-positive breast cancer.
You have a high risk of developing breast cancer.
Studies have found that people who take tamoxifen after the diagnosis of early-stage breast cancer or DCIS for at least five years have a lower risk of breast cancer coming back (recurrence). Studies have also found that for women with a high risk of developing breast cancer, taking tamoxifen for five years reduces the chance that breast cancer will develop.
How tamoxifen works
Tamoxifen blocks the effects of estrogen on hormone receptor-positive breast cancer cells by attaching to the estrogen receptors on the cells. If tamoxifen is attached to the receptor, estrogen can’t attach to the cancer cell — and the cell doesn’t receive estrogen’s signals to grow and multiply.
Tamoxifen also offers other health benefits that aren’t related to treating cancer. While tamoxifen blocks estrogen’s action on breast cells, it has the opposite effect on bone cells. This can help stop bone loss after menopause.
What to expect during tamoxifen treatment
Tamoxifen is available as a pill (brand name: Nolvadex) or as a liquid (brand name: Soltamox). You and your doctor can discuss what’s best for you. In most cases, you take tamoxifen once per day. Most doctors recommend taking tamoxifen at the same time each day.
If you’ve been diagnosed with early-stage, hormone receptor-positive breast cancer, you’ll take tamoxifen for at least five years after surgery to reduce the risk of recurrence. After the first five years, you and your doctor will discuss whether taking another five years of tamoxifen or another five years of an aromatase inhibitor — for a total of 10 years of hormonal therapy after surgery — is right for your unique situation.
If you’ve been diagnosed with hormone receptor-positive DCIS, you’ll take tamoxifen for five years after surgery to reduce the risk of being diagnosed with a recurrence of DCIS, or with invasive breast cancer.
If you’ve been diagnosed with advanced-stage, hormone receptor-positive breast cancer, you’ll take tamoxifen as long as the benefits you’re getting from the medicine outweigh any risks and side effects. Depending on the dose, you may take it once daily; or, less commonly, you may take one dose in the morning and one dose in the evening.
If you are at high risk of developing breast cancer, you’ll take tamoxifen for five years.
Tamoxifen side effects
Like almost all breast cancer medicines, tamoxifen can cause side effects, some of them severe. Tamoxifen causes side effects because it blocks estrogen receptors in both healthy and cancer cells, causing hormonal changes in your body.
The most common side effects of tamoxifen are:
Tamoxifen also may cause serious side effects, including:
Endometrial cancer: Tamoxifen may cause changes to the lining of your uterus, which can lead to endometrial cancer. Tell your doctor right away if you have:
even a small amount of vaginal bleeding or vaginal discharge that is bloody or a rusty brown color
changes in your menstrual periods, including the timing and flow amount
pain or pressure in the area below your belly button
Blood clots: Tamoxifen is known to increase the risk of blood clots. Tell your doctor right away if you have:
sudden chest pain
shortness of breath
coughing that brings up blood
pain, tenderness, or swelling in one or both of your legs
Stroke: Tamoxifen also can increase the risk of having a stroke. it’s a good idea to go directly to the emergency room if you have any symptoms of a stroke, including:
sudden weakness, tingling or numbness in your face, arms, or legs, especially on one side of the body
sudden confusion, or trouble speaking or understanding
sudden trouble seeing in one or both eyes
sudden trouble walking, dizziness, or loss of balance or coordination
sudden severe headache with no known cause
Cataracts: Tamoxifen can increase the risk of needing cataract surgery. Tell your doctor right away if you have symptoms, including:
clouded, blurry, or dimmed vision
trouble seeing at night
sensitivity to light and glare
a need for brighter light for reading and other activities
seeing halos around lights
Liver problems: Tell your doctor right away if you have any of the following signs of liver problems:
yellowing of the skin or the whites of the eyes
dark or brown urine
feeling very tired
loss of appetite
pain on the upper right side of the abdomen
bleeding or bruising more easily than normal
Research suggests that up to half of the women prescribed tamoxifen or other hormonal therapies stop taking the medicine early, in many cases due to side effects such as hot flashes and joint pain.
If you’re having side effects from taking tamoxifen that you can’t tolerate, tell your doctor right away. They may be able to lower your dose or switch you to a different hormonal therapy. They may also be able to offer you guidance or advice on complementary therapies — such as acupuncture, meditation, and exercise — to reduce side effects. They may also discuss certain prescription medications that can reduce the severity of hot flashes if they’re your most troublesome side effect.
You should not take tamoxifen if you’re pregnant or breastfeeding.
Medicines to avoid while taking tamoxifen
Tamoxifen should not be taken at the same time as the aromatase inhibitors Arimidex (chemical name: anastrozole), Femara (chemical name: letrozole), or Aromasin (chemical name exemestane).
If you’re taking tamoxifen, you should also not take medicines that are strong or moderate CYP2D6 inhibitors because they may decrease the efficacy of tamoxifen. Many, but not all, antidepressants are CYP2D6 inhibitors.
Use this list of strong and moderate CYP2D6 inhibitors below as a starting point and talk to your doctor about all the medicines you’re taking and whether they’re compatible with tamoxifen.
Strong CYP2D6 inhibitors:
Wellbutrin (chemical name: bupropion)
Prozac (chemical name: fluoxetine)
Paxil (chemical name: paroxetine)
Cardioquin (chemical name: quinidine)
Mellaril (chemical name: thioridazine)
Trilafon (chemical name: perphenazine)
Orap (chemical name: pimozide)
Anafranil (chemical name: clomipramione)
Ticlid (chemical name: ticlopidine)
Kanusuk (chemical name: terbinafine)
Sensipar (chemical name: cinacalcet)
Moderate CYP2D6 inhibitors:
Cymbalta (chemical name: duloxetine)
Zoloft (chemical name: sertraline)
Benadryl (chemical name: diphenhydramine)
Cordarone (chemical name: amiodarone)
Desyrel (chemical name: trazodone)
Tagamet (chemical name: cimetidine)
Thorazine (chemical name: chlorpromazine)
What happens when you stop taking tamoxifen?
Research suggests that up to half of the women prescribed tamoxifen or other hormonal therapies stop taking the medicine early, in many cases due to side effects such as hot flashes and joint pain.
It’s important to know that stopping tamoxifen increases your risk that breast cancer will come back. If you’re having side effects from taking tamoxifen that you can’t tolerate, tell your doctor right away. They may be able to lower your dose or switch you to a different hormonal therapy or prescribe other medications to address the side effects you're experiencing. They may also be able to offer you guidance or advice on complementary therapies — such as acupuncture, meditation, and exercise — to reduce side effects.
If you do decide to stop taking tamoxifen, your body will undergo hormonal changes that may cause side effects, such as hot flashes, mood swings, weight gain, and periods returning or being heavier. These side effects will likely subside over time.
Real patient reviews
Members of our community discuss their experiences with tamoxifen in the community forum. Here are some of their comments. Remember, it's very important to talk to your doctor about any side effects you're having and ask about ways to manage them.
“I noticed the Tamoxifen giving me heartburn and stomach pain about day eight or nine. I still have this, but [it’s] not as severe most of the time because I take twice as much PPI medication. Within the first two weeks, I [also] began having major problems sleeping and getting exhausted.” —veeder14
“I didn't notice anything until I had irregular periods a few months in. The other side effects didn't start until probably six months in and started with dry mouth/gum irritation. Eventually aches and pain set in, and severe vaginal atrophy probably at year four.” —gb2115
“Tolerated 4 years of tamoxifen. Now fatigue, migraine, dizziness.” —prahan
Read more in our tamoxifen discussion forum.
Paying for Tamoxifen
The cost of tamoxifen may vary. The price you’ll pay depends on the drug manufacturer, your health insurance provider and plan, where you live, and the pharmacy you use.
Note: Your insurance company may require you to get prior authorization before covering tamoxifen.
If you’re prescribed Soltamox — tamoxifen in liquid form — you may be eligible for a Soltamox prescription card.
Learn more about financial assistance and medicine cost-lowering tips.
Tamoxifen tablet prescribing information. Actavis Pharma, Inc. USA. Available at: https://dailymed.nlm.nih.gov/dailymed/fda/fdaDrugXsl.cfm?setid=9b8a4211-120f-4981-ad69-928accb97637&type=display#LINK_176822f9-bb73-491a-a9bc-1f7963074414
Soltamox (liquid tamoxifen) prescribing information. Fortovia Therapeutics Inc. USA. Available at: https://soltamox.com/wp-content/uploads/2019/12/soltamox-pi.pdf
— Last updated on February 28, 2025 at 9:10 PM
