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Tamoxifen

Generic Name: tamoxifen (ta MOX i fen)
Brand Name: Soltamox, ...show all 14 brand names

Medically reviewed on August 4, 2017

What is tamoxifen?

Tamoxifen blocks the actions of estrogen, a female hormone. Certain types of breast cancer require estrogen to grow.

Tamoxifen is used to treat some types of breast cancer in men and women. Tamoxifen is also used to lower a woman's chance of developing breast cancer if she has a high risk (such as a family history of breast cancer).

Tamoxifen may also be used for purposes not listed in this medication guide.

Important Information

You should not use tamoxifen to reduce your risk of breast cancer if you are also taking a blood thinner such as warfarin (Coumadin, Jantoven).

Taking tamoxifen may increase your risk of uterine cancer, stroke, or a blood clot in the lung, which can be fatal.

Do not take tamoxifen if you are pregnant. It could harm the unborn baby. Avoid becoming pregnant while you are using this medicine, and for at least 2 months after your treatment ends.

Before taking this medicine

You should not use tamoxifen if you are allergic to it.

You should not use tamoxifen to reduce your risk of breast cancer if you are also taking a blood thinner such as warfarin (Coumadin, Jantoven).

Do not take tamoxifen if you are pregnant. It could harm the unborn baby. Avoid becoming pregnant while you are using this medicine, and for at least 2 months after your treatment ends.

Hormonal contraception (such as birth control pills, injections, implants, skin patches, and vaginal rings) may not be effective enough to prevent pregnancy while taking tamoxifen. Ask your doctor about using non hormonal birth control (condom, diaphragm with spermicide, or intrauterine device/IUD).

If you are taking tamoxifen to reduce your risk of breast cancer, you may need to take your first dose while you are having a menstrual period. You may also need to have a pregnancy test before you start taking tamoxifen, to make sure you are not pregnant. Follow your doctor's instructions.

Taking tamoxifen may increase your risk of uterine cancer, stroke, or a blood clot in the lung, which can be fatal. Talk with your doctor about your specific risks in taking this medicine.

To make sure tamoxifen is safe for you, tell your doctor if you have:

It is not known whether tamoxifen passes into breast milk or if it could harm a nursing baby. This medicine may slow breast milk production. You should not breast-feed while taking tamoxifen.

How should I take tamoxifen?

Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

Tamoxifen can be taken with or without food.

While using tamoxifen, you may need frequent blood tests.

If you need surgery or medical tests or if you will be on bed rest, you may need to stop using this medicine for a short time. Any doctor or surgeon who treats you should know that you are taking tamoxifen.

Have regular physical exams and mammograms, and self-examine your breasts for lumps on a monthly basis while using this medicine.

Use tamoxifen regularly to get the most benefit. Get your prescription refilled before you run out of medicine completely. You may need to keep using this medication for up to 5 years.

Store at room temperature away from moisture, heat, or cold. Do not freeze.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking tamoxifen?

This medicine can pass into body fluids (urine, feces, vomit). Caregivers should wear rubber gloves while cleaning up a patient's body fluids, handling contaminated trash or laundry or changing diapers. Wash hands before and after removing gloves. Wash soiled clothing and linens separately from other laundry.

Tamoxifen side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Tamoxifen can increase your risk of stroke or blood clots. Call your doctor at once if you have:

  • signs of a stroke--sudden numbness or weakness (especially on one side of the body), sudden severe headache, slurred speech, problems with vision or balance;

  • signs of a blood clot in the lung--chest pain, sudden cough, wheezing, rapid breathing, coughing up blood; or

  • signs of a blood clot in your leg--pain, swelling, warmth, or redness in one or both legs.

Also call your doctor at once if you have:

  • blurred vision, tunnel vision, eye pain, or seeing halos around lights;

  • unusual vaginal bleeding or discharge;

  • changes in your menstrual periods;

  • pain or pressure in your pelvic area;

  • a new breast lump;

  • liver problems--nausea, upper stomach pain, itching, tired feeling, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes); or

  • high levels of calcium in your blood--vomiting, constipation, increased thirst or urination, muscle weakness, bone pain, confusion, lack of energy, or tired feeling.

Common side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

See also: Side effects (in more detail)

Tamoxifen dosing information

Usual Adult Dose for Breast Cancer:

Metastatic breast cancer in women and men:
20 to 40 mg orally daily for 5 years; doses greater than 20 mg should be given in divided doses (morning and evening)

DCIS following breast surgery and radiation:
20 mg orally daily for 5 years

To reduce the incidence of breast cancer in women at high risk for breast cancer:
20 mg orally daily for 5 years

Comments:
-There are no data to support the use of this drug other than for 5 years.

Uses:
-Metastatic For metastatic breast cancer in women and men. In premenopausal women with metastatic breast cancer, this drug is an alternative to oophorectomy or ovarian irradiation. Patients whose tumors are estrogen receptor positive are more likely to benefit.
-Ductal Carcinoma in Situ (DCIS): In women with DCIS, following breast surgery and radiation, to reduce the risk of invasive breast cancer.
-Reduction in Breast Cancer Incidence in High Risk Women: To reduce the incidence of breast cancer in women at high risk. "High risk" is defined as women at least 35 years of age with a 5-year predicted risk of breast cancer greater than or equal to 1.67%, as calculated by the Gail Model.

Usual Adult Dose for Breast Cancer -- Adjuvant:

20 mg orally once daily or 10 mg orally 2 times daily
Duration of therapy: Up to 5 years

Comments:
-There are no data to support the use of this drug other than for 5 years.

Use: For the treatment of node-positive breast cancer in postmenopausal women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation

Usual Pediatric Dose for McCune-Albright Syndrome:

Girls 2 to 10 years with McCune-Albright Syndrome and precocious puberty:
20 mg orally once daily
Duration of therapy: Up to 12 months

Use: McCune-Albright Syndrome; precocious puberty

Usual Pediatric Dose for Precocious Puberty:

Girls 2 to 10 years with McCune-Albright Syndrome and precocious puberty:
20 mg orally once daily
Duration of therapy: Up to 12 months

Use: McCune-Albright Syndrome; precocious puberty

What other drugs will affect tamoxifen?

Many drugs can interact with tamoxifen, and some drugs should not be used together. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide. Tell your doctor about all medicines you use, and those you start or stop using during your treatment with tamoxifen. Give a list of all your medicines to any healthcare provider who treats you.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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