Tamoxifen (brand names: Nolvadex, Soltamox) is a selective estrogen receptor modulator (SERM) used:
after surgery to reduce the risk of hormone receptor-positive, early-stage breast cancer coming back (recurring) in women or men
to treat women or men diagnosed with advanced-stage, hormone receptor-positive breast cancer
after surgery to reduce the risk of invasive breast cancer in women diagnosed with hormone receptor-positive DCIS (ductal carcinoma in situ)
to reduce the risk of breast cancer in women with a higher-than-average risk of the disease who haven’t been diagnosed
It’s important to know that tamoxifen should not be taken at the same time as the aromatase inhibitors Arimidex (chemical name: anastrozole) or Femara (chemical name: letrozole).
How tamoxifen works
Tamoxifen blocks the effects of estrogen on hormone receptor-positive breast cancer cells by sitting in the estrogen receptors on the cells. If tamoxifen is in the receptor, estrogen can’t attach to the cancer cell and the cell doesn’t receive estrogen’s signals to grow and multiply.
Tamoxifen won’t work on hormone receptor-negative breast cancer.
Is tamoxifen right for you?
Tamoxifen is used to treat pre- and post-menopausal women and men diagnosed with either early-stage or advanced-stage, hormone receptor-positive breast cancer.
Tamoxifen is also used after surgery to reduce the risk of invasive breast cancer in women who have been diagnosed with hormone receptor-positive DCIS.
Tamoxifen is also used to reduce breast cancer risk in women with a higher-than-average risk of the disease who haven’t been diagnosed.
You should not take tamoxifen if you have a history of blood clots or take blood-thinning medicine. Tamoxifen increases the risk of blood clots.
You should not take tamoxifen if you are breastfeeding, pregnant, trying to get pregnant, or if there is any chance that you could be pregnant. Tamoxifen may cause damage to developing embryos. You should use an effective non-hormonal type of birth control while you are taking tamoxifen. Ask your doctor which type of non-hormonal birth control would be best for you. You should use the birth control for at least two months after your last dose of tamoxifen.
What to expect during tamoxifen treatment
Tamoxifen is available as a pill or as a liquid, so you can decide which form is easiest for you to take. In most cases, you take tamoxifen once per day.
If you’ve been diagnosed with early-stage, hormone receptor-positive breast cancer you take tamoxifen for five years after surgery to reduce the risk of recurrence. After the first five years, you and your doctor would 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 take tamoxifen for five years after surgery to reduce the risk of being diagnosed with invasive breast cancer.
If you’ve been diagnosed with advanced-stage, hormone receptor-positive breast cancer, you 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 one dose in the morning and one dose in the evening.
If you have a higher-than-average risk of breast cancer, you take tamoxifen for five years.
If you’re taking tamoxifen, you should not take medicines that are strong or moderate CYP2D6 inhibitors because they decrease the effects of tamoxifen. Many, but not all, antidepressants are CYP2D6 inhibitors and should not be taken with tamoxifen. Use the 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:
Wellbrutrin (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)
Tamoxifen side effects
Like almost all breast cancer medicines, tamoxifen can cause side effects, some of them severe.
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 another hormonal therapy medicine stop taking the medicine early, in many cases because of troubling or painful side effects. Still, it’s very important to know that taking hormonal therapy for the prescribed amount of time can reduce the risk of recurrence by 50% and can reduce the risk of dying from breast cancer by about 30%.
If you’re having problematic side effects from taking tamoxifen or another hormonal therapy medicine, talk to your doctor right away. There are steps you can take to ease some of the most common side effects:
medicines have been shown to reduce the number and severity of hot flashes
complementary and alternative therapies, such as acupuncture and mindfulness meditation, have been shown to ease pain, including joint pain
exercise has been shown to ease joint pain and increase bone density
You also may be able to switch to a different hormonal therapy medicine or take a different dose.
Paying for tamoxifen
Because tamoxifen has been available as a generic medicine for many years, there are no pharmaceutical company support programs for it.
If your doctor prescribes tamoxifen and you have problems paying for it, ask your care team about programs in your area that may be able to help.
If you’re prescribed Soltamox — tamoxifen in liquid form — you may be eligible for a Soltamox prescription card.
Learn more about Paying for Your Care, including information on additional types of financial assistance and 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 July 27, 2022, 1:54 PM