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. It 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.
Do not use tamoxifen if you are pregnant. It could harm the unborn baby. Use a barrier form of birth control (such as a condom or diaphragm with spermicide) while you are using this medication and for at least 2 months after your treatment ends. You should not use tamoxifen if you are allergic to it, or if you have a history of blood clots in your veins or your lungs, or if you are also taking a blood thinner such as warfarin (Coumadin).
Atrial Fibrillation – Stroke Prevention Guidelines & Treatment Options
Before using this medicine, tell your doctor if you have liver disease, high triglycerides (a type of fat in the blood), a history of cataract, or a history of stroke or blood clot. Also tell your doctor if you if you are receiving chemotherapy or radiation treatment.
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 this medicine, 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 medication.
To make sure this medication is not causing harmful effects, your doctor may want you to have mammograms and to perform routine breast self exams on a regular basis. Your liver function may also need to be tested. Visit your doctor regularly.
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:
a history of stroke or blood clot;
high cholesterol or triglycerides (a type of fat in the blood);
a history of cataracts; or
if you are receiving chemotherapy or radiation.
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 to tamoxifen: 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 tamoxifen ide effects may include:
vaginal discharge; or
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:
For the treatment of metastatic breast cancer in women and men:
20 to 40 mg orally Dosages greater than 20 mg should be given in divided doses (morning and evening).
For the treatment of women with Ductal Carcinoma in Situ, 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.
Usual Adult Dose for Breast Cancer – Adjuvant:
For the treatment of node-positive breast cancer in postmenopausal women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation:
10 mg orally 2 to 3 times a day for 5 years.
Usual Adult Dose for Breast Cancer – Palliative:
10 to 20 mg orally twice a day
A beneficial response may not be evident for several months after initiation of therapy.
Usual Pediatric Dose for McCune-Albright Syndrome:
For use in girls age 2 to 10 years with McCune-Albright Syndrome and precocious puberty:
20 mg once a day. The duration of treatment is up to 12 months.
Usual Pediatric Dose for Precocious Puberty:
For use in girls age 2 to 10 years with McCune-Albright Syndrome and precocious puberty:
20 mg once a day. The duration of treatment is up to 12 months.
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.
Tamoxifen Side Effects
Commonly reported side effects of tamoxifen include vaginal hemorrhage, nausea, weight loss, amenorrhea, vaginal discharge, hot flash, fluid retention, and skin changes. Other side effects include sepsis, infection, edema, diarrhea, constipation, weight gain, alopecia, menstrual disease, vomiting, ostealgia, increased serum aspartate aminotransferase, cough, and oligomenorrhea. See below for a comprehensive list of adverse effects.
For the Consumer
Applies to tamoxifen: oral solution, oral tablet
Because of the way this medicine acts on the body, there is a chance that it might cause unwanted effects that may not occur until months or years after the medicine is used. Tamoxifen increases the chance of cancer of the uterus (womb) in some women taking it. Tamoxifen may cause blockages to form in a vein, lung, or brain. In women, tamoxifen may cause cancer or other problems of the uterus (womb). It also causes liver cancer in rats. In addition, tamoxifen has been reported to cause cataracts and other eye problems. Discuss these possible effects with your doctor.
As well as its needed effects, tamoxifen may cause unwanted side effects that require medical attention.
If any of the following side effects occur while taking tamoxifen, check with your doctor immediately:
Less common or rare
blistering, peeling, or loosening of the skin and mucous membranes
cataracts in the eyes or other eye problems
change in vaginal discharge
lower back or side pain
pain or feeling of pressure in the pelvis
pain or swelling in the legs
pain, redness, or swelling in your arm or leg
painful or difficult urination
rapid shallow breathing
shortness of breath or trouble with breathing
skin rash or itching over the entire body
weakness or sleepiness
yellow eyes or skin
Incidence not known
difficulty with breathing
joint or muscle pain
large, hard skin blisters
large hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, and sex organs
loss of appetite
pain in the stomach or side, possibly radiating to the back
red, irritated eyes
red skin lesions, often with a purple center
sores, ulcers or white spots in the mouth or on the lips
unusual tiredness or weakness
Some tamoxifen side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:
Absent, missed, or irregular periods
decrease in the amount of urine
feeling of warmth
noisy, rattling breathing
redness of the face, neck, arms and occasionally, upper chest
stopping of menstrual bleeding
swelling of the fingers, hands, feet, or lower legs
troubled breathing at rest
weight gain or loss
white or brownish vaginal discharge
Less common or rare
Abdominal or stomach cramps
black, tarry stools
blood in the urine or stools
bluish color changes in skin color
decreased interest in sexual intercourse
feeling sad or empty
hair loss or thinning of the hair
inability to have or keep an erection
itching in the genital area
loss of interest or pleasure
loss in sexual ability, desire, drive, or performance
nausea or vomiting (mild)
pinpoint red spots on the skin
skin rash or dryness
stomach or pelvic discomfort, aching, or heaviness
trouble with sleeping
unusual bleeding or bruising
For Healthcare Professionals
Applies to tamoxifen: compounding powder, oral solution, oral tablet
In general, hot flashes, nausea, and vomiting have been the most commonly reported adverse effects, occurring in up to 25% of patients.
Oncologic side effects including numerous endometrial abnormalities have been reported with tamoxifen use. These have included both endometrial adenocarcinoma (incidence rate per 1,000 women-years of 2.20 for tamoxifen versus 0.71 for placebo) and uterine sarcoma (incidence rate per 1,000 women-years of 0.17 for tamoxifen versus 0.04 for placebo). In most women treated with tamoxifen, the endometrium remains atrophic. However, hyperplasia, metaplasia, atypical hyperplasia, and endometrial polyps have also been reported.
The National Surgical Adjuvant Breast and Bowel Cancer (NSABP) B-14 trial evaluated the incidence of endometrial cancer in women with node-negative, estrogen receptor-positive, invasive breast cancer randomized to receive either placebo or tamoxifen 20 mg per day for five years after undergoing primary therapy. Compared with the placebo group, the relative risk of endometrial cancer among tamoxifen-treated women was 7.5.
In general, patients should be examined for preexisting endometrial lesions prior to starting tamoxifen therapy. The benefits and timing of routine endometrial screening, after initial scrounge, have yet to be defined. However, any postmenopausal bleeding or abnormal bleeding in premenopausal women should prompt a gynecological evaluation.
Genitourinary side effects including endometriosis, vaginal bleeding, vaginal discharge, amenorrhea, altered menses, and oligomenorrhea have been reported in up to 24% of patients. However, these effects have rarely necessitated dosage reduction or drug withdrawal. Recurrent vulvovaginal candidiasis in postmenopausal women has been associated with long term treatment. Priapism and suppression of spermatogenesis have been reported in male patients treated with tamoxifen.
Musculoskeletal side effects including pain and bone pain or bone “flare” have been reported in some patients following onset of tamoxifen therapy and generally subside rapidly. Severe hypercalcemia or pancytopenia may occur in conjunction with these symptoms. In addition, patients with soft tissue disease may experience an initial increase in lesion size as well as local erythema during initiation of therapy. Other rheumatologic side effects have included a report of an acute, symmetrical inflammatory polyarthropathy.
Metabolic side effects have included severe hypercalcemia. Severe hypertriglyceridemia has been reported in one patient. The drug has been shown to inhibit bone turnover in women over 70 years old.
Life-threatening hypercalcemia may occur during initial therapy with tamoxifen in patients with bone metastases. Monitoring of serum calcium levels during early therapy is recommended for patients in whom bone metastases are present or are suspected. In cases of severe hypercalcemia, discontinuation of tamoxifen may be warranted, with reinstitution at a lower dose once calcium levels have normalized.
Bone mineral density studies have failed to find evidence of increased risk of osteoporosis in women treated with tamoxifen. One study noted a significant reduction in serum osteocalcin and alkaline phosphatase, indicating that tamoxifen may actually decrease the rate of trabecular bone resorption.
Hepatic side effects have included elevation in liver function tests, jaundice, peliosis hepatitis, steatohepatitis, cholestasis, and massive hepatic necrosis. While severe hepatic effects are rare, fatalities have been reported.
Hematologic side effects have been uncommon and have included thrombocytopenia (1%), leukopenia, and agranulocytosis. Two cases of cerebral sinus thrombosis have also been reported. Small, but clinically insignificant, decreases in antithrombin III and fibrinogen have been reported.
A prospective study involving 63 patients evaluated the risk of ocular toxicity due to tamoxifen 20 mg daily for a mean duration of 25 months (range: 6 to 51 months). Ocular toxicity, characterized by decreased visual acuity and retinopathy, occurred in 4 (6.3%) patients. Irreversible subepithelial corneal opacities were noted in one patient. Earlier reports suggested ocular toxicity was only associated with high-dose (>180 mg per day) therapy. However, this study and other recent case reports support a risk with currently accepted dosage regimens.
Ocular side effects including bilateral optic neuritis, retinopathy, and subepithelial opacities have been reported. Several cases of keratopathy have also been reported.
Several studies evaluating the effect of tamoxifen on antithrombin III, fibrinogen, and platelets have been unable to provide clarification of thromboembolic risk in tamoxifen treated patients. In addition, despite its antiestrogenic activity, evidence is lacking to support a tamoxifen-associated increase in cardiovascular risk. One study concluded that tamoxifen and prior surgery, fracture, or immobilization were associated with a significantly increased risk of developing a venous thromboembolism. Another study found a decreased risk of myocardial infarction.
In one study of 8 premenopausal and 46 postmenopausal women with advanced breast cancer, tamoxifen 10 mg three times daily produced no effect on total cholesterol, triglycerides, or free fatty acids. A significant increase in HDL and subsequent increase in HDL/total cholesterol ratio were noted in addition to a significant reduction in LDL cholesterol. Overall, tamoxifen appeared to exert a favorable effect on the lipid profile.
One five year study has reported total serum cholesterol, LDL cholesterol, and lipoprotein to be significantly lower and apolipoprotein A1 levels significantly higher in 30 tamoxifen recipients compared with the 32 patients who did not receive tamoxifen. Apolipoprotein B levels were reported to have increased to a greater extent in the group which did not receive tamoxifen. After five years, fibrinogen level decreases and triglyceride level increases in the tamoxifen group were of borderline statistical significance. In general, the favorable changes in the lipid, lipoprotein, and fibrinogen levels seen early in tamoxifen therapy in postmenopausal women were reported to have continued to be seen five years into the treatment regimen.
Cardiovascular side effects including stroke (incidence rate per 1,000 women years was 1.43 for tamoxifen versus 1.00 for placebo) have been reported. Hot flushes (which may be severe in up to 22.7% of patients), edema (25%), phlebitis (1%), and thromboembolism have also been reported.
Respiratory side effects including pulmonary embolism (incidence rate per 1,000 women-years was 0.75 for tamoxifen versus 0.25 for placebo) have been reported. Cough as well as a case of exacerbation of asthma have also been reported.
Endocrine side effects have included elevations in T4 in the absence of clinical hyperthyroidism. This may be due to tamoxifen-induced elevations in circulating thyroid binding globulin. In addition, tamoxifen suppresses prolactin release in response to breast stimulation in puerperal women. Up to 30% of male breast cancer patients may experience a decrease in libido when treated with tamoxifen.
Psychiatric side effects including depression and delusional syndromes have been reported rarely.
Immunologic side effects have included a case report of purpuric vasculitis.
Rechallenge with tamoxifen resulted in reappearance of lesions.
Other side effects have included radiation recall and anorexia.
Tamoxifen-induced anorexia has been associated with fatty acid synthase inhibition in the ventromedial nucleus of the hypothalamus and accumulation of malonyl-CoA.
Dermatologic side effects including four cases of hair loss have been reported. One of those cases involved tamoxifen-induced total alopecia. A case of repigmentation following graying of the hair in a 68-year-old patient has also been reported.
One study has reported that when compared to healthy controls who were not using the drug, tamoxifen users exhibited significantly worse performance on visual memory, word fluency, immediate verbal memory, visuo-spatial ability, and processing speed tasks.
Nervous system side effects including adverse cognitive effects have been reported.