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Drug Profile

The information on this site is intended to supplement and enhance, not replace, the advice of a physician who is familiar with your medical history. Decisions about your health should always be made ONLY after detailed conversation with your doctor.

Limited Use [what does this mean?]
Generic drug name: tamoxifen (ta MOX i fen)
Brand name(s): SOLTAMOX
GENERIC: available FAMILY: Anti-Estrogens
Find the drug label by searching at DailyMed.

Pregnancy and Breast-feeding Warnings [top]

Pregnancy Warning

Tamoxifen caused fetal harm in animal studies, including abortions, premature delivery, and death. Because of the potential for serious adverse effects to the fetus, this drug should not be used by pregnant women.

Breast-feeding Warning

No information is available from either human or animal studies. However, it is likely that this drug is excreted in human milk, and because of the potential for serious adverse effects in nursing infants, you should not take this drug while nursing.

Safety Warnings For This Drug [top]

FDA BLACK-BOX WARNING

WARNING: UTERINE MALIGNANCIES and THROMBOEMBOLIC EVENTS[1]

Serious and life-threatening events from the use of tamoxifen include uterine malignancies, stroke and pulmonary embolism. Fatal cases of each type of event have occurred.

Incidence rates per 1,000 women-years for these events were estimated from the National Surgical Adjuvant Breast and Bowel Project P-1 trial in women at high risk for breast cancer:

  • Endometrial adenocarcinoma: 2.20 for tamoxifen versus 0.71 for placebo
  • Uterine sarcoma: 0.17 for tamoxifen versus 0.04 for placebo
  • Stroke: 1.43 for tamoxifen versus 1.00 for placebo
  • Pulmonary embolism (blood clots in the lungs): 0.75 for tamoxifen versus 0.25 for placebo

Doctors should discuss the potential benefits of tamoxifen versus the potential risks of these serious events with women at high risk of breast cancer and women with ductal carcinoma in situ who are considering tamoxifen to reduce the risk of developing breast cancer. For most patients already diagnosed with breast cancer, the benefits of tamoxifen outweigh its risks.

Facts About This Drug [top]

Tamoxifen is listed as a Limited Use drug.

Tamoxifen was approved by the Food and Drug Administration (FDA) in 1977 and is now approved to be used in several different situations involving breast cancer.[2] In 1998, the drug was approved for the reduction in breast cancer incidence in women at high risk of developing the disease. High risk was defined as a five-year predicted risk of breast cancer of at least 1.67%.

Confusion soon erupted over whether the FDA approved tamoxifen for all...

Tamoxifen is listed as a Limited Use drug.

Tamoxifen was approved by the Food and Drug Administration (FDA) in 1977 and is now approved to be used in several different situations involving breast cancer.[2] In 1998, the drug was approved for the reduction in breast cancer incidence in women at high risk of developing the disease. High risk was defined as a five-year predicted risk of breast cancer of at least 1.67%.

Confusion soon erupted over whether the FDA approved tamoxifen for all women 60 years of age and older without other risk factors for breast cancer. The news media were initially reporting that regardless of other factors, all women 60 and older were at a five-year predicted risk of 1.67% (th%e high-risk category) for developing breast cancer and thus were eligible to receive tamoxifen. This is not the case: Not all women over 60 are at a high risk of developing breast cancer, and not all women over 60 should be receiving tamoxifen to reduce the risk of breast cancer.

Adverse effects

The most serious adverse effects of tamoxifen include endometrial cancer, uterine sarcoma, deep vein thrombosis (blood clots in large veins, most often in the legs), pulmonary embolism (blood clots in the lungs) and, rarely, liver cancer.[2]

Uterine sarcoma

In 2006, there were three case reports of women who developed a type of cancer known as uterine sarcoma during or following treatment with tamoxifen for breast cancer. Two of these three women died.[3]

Endometrial cancer, involving the lining of the uterus, is the most common form of cancer in this organ, accounting for approximately 95% of all uterine cancers. Uterine sarcoma is a rare cancer of the uterus, accounting for 2-5% of all uterine cancers. Because it is usually diagnosed at a more advanced stage than other uterine tumors, women diagnosed with this cancer usually have a poorer outcome and shorter survival than others.

Evidence of the risk of uterine sarcoma with tamoxifen use — which led to the FDA’s decision to include a black-box warning on its label — came in a letter to The New England Journal of Medicine from FDA staff in June 2002.[4] The FDA found that between 1978, when tamoxifen was first marketed in the U.S., and April 2001, there were 43 cases of uterine sarcoma in women who had received the drug that had been reported to the agency or published in the medical literature. In addition, internationally, this cancer was reported to have developed in 116 women who had used tamoxifen for breast cancer.

Diabetes

A study published in 2011 reviewed information to determine if there was an association between tamoxifen use and the occurrence of new diabetes in older breast cancer survivors. Based on the information examined in the study, the authors found that in this patient population, there was an increased risk of new diabetes.[5]

Studies show ...

The large clinical trial (over 13,000 women) that was used to gain approval for tamoxifen in reducing breast cancer incidence in high-risk women compared tamoxifen with a placebo over a period of five years.[6]

The incidence of breast cancer was reduced by 2.9 cases per year out of 1,000 women using tamoxifen. However, there was an excess of 1.4 cases of endometrial cancer per year out of 1,000 women taking tamoxifen. For blood clot in the lungs, blood clot in the veins and stroke, the number of excess cases that occurred with tamoxifen use compared with placebo were 0.5, 0.5 and 0.4, respectively, per year out of 1,000 women taking tamoxifen. Overall, there was an excess of 2.8 cases of a potentially life-threatening adverse drug reactions per year out of 1,000 women on tamoxifen. In other words, for each reduction of one case in the incidence of breast cancer, there was about one case of a potentially life-threatening drug reaction with the use of tamoxifen.

In this study, the benefit of tamoxifen equaled its serious risks — it was a wash. However, there was also an additional increased risk of cataracts and cataract surgery in women using tamoxifen.

In 2009, The Medical Letter on Drugs and Therapeutics published an article reviewing information on the interaction of tamoxifen and selective serotonin reuptake inhibitors (SSRIs), a class of drugs used to treat depression. The article summarized the results of two observational studies on the effect of SSRIs on tamoxifen and the success rate of tamoxifen in preventing recurrence of breast cancer. One study found a higher two-year recurrence rate, and the other study found no increase in the recurrence rate.[7]

In 2020, PLoS One published an article warning that tamoxifen can increase the risk of developing or worsening fatty liver (a condition in which excess fat builds up in the liver).[8]

Regulatory actions surrounding tamoxifen

2002: In June, the FDA required a black-box warning, the strongest type of warning that the agency can require, on the product label for the drug. The warning concerns increased risks of sometimes fatal uterine cancers, stroke and blood clots in the lungs (pulmonary embolism) in women at high risk of breast cancer who use tamoxifen to reduce the incidence of breast cancer and in women with a form of breast cancer called ductal carcinoma in situ (DCIS). DCIS is characterized by abnormal cells that involve only the lining of a duct. Such cells have not yet spread outside the duct to other breast tissues. It is a noninvasive cancer that can become invasive in some cases.

The June labeling change was aimed at women who are considering tamoxifen to reduce the incidence of breast cancer or those with DCIS for whom a survival benefit of the drug has not been demonstrated. At this time, the known benefits of tamoxifen outweigh its risks in women already diagnosed with other kinds of breast cancer.

Before You Use This Drug [top]

Do not use if you have or have had:

  • blood-clotting problems
  • pregnancy or are breast-feeding
  • stroke
  • uterine malignancies
  • pulmonary emboli
  • deep vein thrombosis (DVT)

Tell your doctor if you have or have had:

  • allergy to tamoxifen
  • blood disorder
  • cataracts or other vision problems
  • high cholesterol

Tell your doctor about any other drugs you take, including aspirin, herbs, vitamins, and other nonprescription products. Ask for exams of your eyes[6] and for a test to detect endometrial cancer before you start to take tamoxifen.[9]

When You Use This Drug [top]

  • 8See your doctor regularly for close monitoring while taking this drug.
  • Continue taking this drug even if you get an upset stomach. However, check with your doctor if vomiting occurs shortly after drug is taken.
  • Take analgesics if needed for pain, which often occurs when tamoxifen is started but then subsides.
  • For women: Tamoxifen may increase fertility. Do not become pregnant. Use barrier or nonhormonal contraceptives. Tell your doctor immediately if you suspect you are pregnant.

How to Use This Drug [top]

  • If you miss a dose, take it as soon as you remember, but skip it if it is almost time for the next dose. Do not take double doses.
  • Do not share your medication with others.
  • Take the drug at the same time(s) each day.
  • Store at room temperature with lid on tightly. Do not store in the bathroom. Do not expose to heat, moisture, or strong light. Keep out of reach of children.

Interactions with Other Drugs [top]

The following drugs, biologics (e.g., vaccines, therapeutic antibodies), or foods are listed in Evaluations of Drug Interactions 2003 as causing “highly clinically significant” or “clinically significant” interactions when used together with any of the drugs in this section. In some sections with multiple drugs, the interaction may have been reported for one but not all drugs in this section, but we include the interaction because the drugs in this section are similar to one another. We have also included potentially serious interactions listed in the drug’s FDA-approved professional package insert or in published medical journal articles. There may be other drugs, especially those in the families of drugs listed below, that also will react with this drug to cause severe adverse effects. Make sure to tell your doctor and pharmacist the drugs you are taking and tell them if you are taking any of these interacting drugs:

aminoglutethimide, AVELOX, clopidogrel, COUMADIN, CYTADREN,[10] ESTRADERM, estrogen, moxifloxacin, NORVIR, PLAVIX, PREMARIN, ritonavir, warfarin.

Adverse Effects [top]

Call your doctor immediately if you experience:

For both women and men:

  • confusion
  • blistering, peeling, or loosening of skin and mucous membranes
  • blurred vision
  • yellowing of skin or eyes
  • shortness of breath
  • swelling or pain in legs
  • weakness or sleepiness
  • chest pain, anxiety, cough, fainting, fast heartbeat, sudden shortness of breath, trouble breathing, dizziness or lightheadedness

For women:

  • pain or pressure in pelvis
  • change in vaginal discharge
  • bleeding

Call your doctor if these symptoms continue:

For both men and women:

  • headache
  • mild nausea or vomiting
  • skin rash or dryness
  • transient bone pain

For women:

  • hot flashes
  • weight gain
  • changes in menstrual periods
  • itching in genital area
  • vaginal discharge

For men:

  • impotence or decreased interest in sex

Periodic Tests[top]

Ask your doctor which of these tests should be done periodically while you are taking this drug:

For both women and men:

  • blood levels of calcium
  • blood levels of cholesterol and triglycerides
  • complete blood count
  • liver function tests
  • eye exams

For women:

  • gynecologic examinations

For women taking the drug to reduce the risk of breast cancer:

  • breast examinations
  • mammograms

last reviewed April 30, 2021