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Quick facts
- How it is given
- oral
- Type
- human prescription drug
- RxNorm ID
- 198240
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
INDICATIONS AND USAGE Metastatic Breast Cancer: Tamoxifen citrate tablets are effective in the treatment of metastatic breast cancer in women and men. In premenopausal women with metastatic breast cancer, tamoxifen citrate tablets are an alternative to oophorectomy or ovarian irradiation. Available evidence indicates that patients whose tumors are estrogen receptor positive are more likely to benefit from tamoxifen citrate tablets therapy. Adjuvant Treatment of Breast Cancer: Tamoxifen citrate tablets are indicated for the treatment of node-positive breast cancer in women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation. In some tamoxifen citrate adjuvant studies, most of the benefit to date has been in the subgroup with four or more positive axillary nodes. Tamoxifen citrate tablets are indicated for the treatment of axillary node-negative breast cancer in women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation. The estrogen and progesterone receptor values may help to predict whether adjuvant tamoxifen citrate tablets therapy are likely to be beneficial. Tamoxifen citrate tablets reduces the occurrence of contralateral breast cancer in patients receiving adjuvant tamoxifen citrate tablets therapy for breast cancer. Ductal Carcinoma in Situ (DCIS): In women with DCIS, following breast surgery and radiation, tamoxifen citrate tablets are indicated to reduce the risk of invasive breast cancer (see BOXED WARNING at the beginning of the label). The decision regarding therapy with tamoxifen citrate tablets for the reduction in breast cancer incidence should be based upon an individual assessment of the benefits and risks of tamoxifen citrate tablets therapy. Current data from clinical trials support five years of adjuvant tamoxifen citrate tablets therapy for patients with breast cancer. Reduction in Breast Cancer Incidence in High Risk Women: Tamoxifen citrate tablets are indicated to reduce the incidence of breast cancer in women at high risk for breast cancer. This effect was shown in a study of 5 years planned duration with a median follow-up of 4.2 years. […]
About this medicine
DESCRIPTION Tamoxifen citrate tablets, USP a nonsteroidal antiestrogen, are for oral administration. Tamoxifen citrate tablets are available as: 10 mg Tablets: Each tablet contains 15.2 mg of tamoxifen citrate USP equivalent to 10 mg of tamoxifen. 20 mg Tablets: Each tablet contains 30.4 mg of tamoxifen citrate USP equivalent to 20 mg of tamoxifen. Inactive Ingredients: corn starch (maize), croscarmellose sodium, hypromellose, lactose monohydrate, magnesium stearate, polyethylene glycol, povidone and titanium dioxide. Chemically, tamoxifen citrate is the trans-isomer of a triphenylethylene derivative. The chemical name is (Z)2-[4-(1,2-diphenyl-1-butenyl) phenoxy]-N, N-dimethylethanamine 2 hydroxy-1,2,3- propanetricarboxylate (1:1). The structural and molecular formulas are: Tamoxifen citrate has a molecular weight of 563.62, the pKa' is 8.85, the equilibrium solubility in water at 37°C is 0.3159 mg/mL and in 0.02 N HCl at 37°C, it is 0.4045 mg/mL. Chemical Structure
Who should not take it
CONTRAINDICATIONS Tamoxifen citrate tablets are contraindicated in patients with known hypersensitivity to the drug or any of its ingredients. Reduction in Breast Cancer Incidence in High Risk Women and Women with DCIS: Tamoxifen citrate tablets are contraindicated in women who require concomitant coumarin-type anticoagulant therapy or in women with a history of deep vein thrombosis or pulmonary embolus.
Warnings
WARNINGS Effects in Metastatic Breast Cancer Patients: As with other additive hormonal therapy (estrogens and androgens), hypercalcemia has been reported in some breast cancer patients with bone metastases within a few weeks of starting treatment with tamoxifen citrate. If hypercalcemia does occur, appropriate measures should be taken and, if severe, tamoxifen citrate should be discontinued. Effects on the Uterus-Endometrial Cancer and Uterine Sarcoma: An increased incidence of uterine malignancies has been reported in association with tamoxifen citrate treatment. The underlying mechanism is unknown, but may be related to the estrogen-like effect of tamoxifen citrate. Most uterine malignancies seen in association with tamoxifen citrate are classified as adenocarcinoma of the endometrium. However, rare uterine sarcomas, including malignant mixed mullerian tumors (MMMT), have also been reported. Uterine sarcoma is generally associated with a higher FIGO stage (III/IV) at diagnosis, poorer prognosis, and shorter survival. Uterine sarcoma has been reported to occur more frequently among long-term users (≥ 2 years) of tamoxifen citrate than non-users. Some of the uterine malignancies (endometrial carcinoma or uterine sarcoma) have been fatal. In the NSABP P-1 trial, among participants randomized to tamoxifen citrate there was a statistically significant increase in the incidence of endometrial cancer (33 cases of invasive endometrial cancer, compared to 14 cases among participants randomized to placebo (RR=2.48, 95% CI: 1.27 to 4.92). The 33 cases in participants receiving tamoxifen citrate were FIGO Stage I, including 20 IA, 12 IB, and 1 IC endometrial adenocarcinomas. In participants randomized to placebo, 13 were FIGO Stage I (8 IA and 5 IB) and 1 was FIGO Stage IV. Five women on tamoxifen citrate and 1 on placebo received postoperative radiation therapy in addition to surgery. This increase was primarily observed among women at least 50 years of age at the time of randomization (26 cases of invasive endometrial cancer, compared to 6 cases among participants randomized to placebo (RR=4.50, 95% CI: 1.78 to 13.16). […]
Reported side effects
ADVERSE REACTIONS Adverse reactions to tamoxifen citrate are relatively mild and rarely severe enough to require discontinuation of treatment in breast cancer patients. Continued clinical studies have resulted in further information which better indicates the incidence of adverse reactions with tamoxifen citrate as compared to placebo. Metastatic Breast Cancer: Increased bone and tumor pain and, also, local disease flare have occurred, which are sometimes associated with a good tumor response. Patients with increased bone pain may require additional analgesics. Patients with soft tissue disease may have sudden increases in the size of pre-existing lesions, sometimes associated with marked erythema within and surrounding the lesions and/or the development of new lesions. When they occur, the bone pain or disease flare are seen shortly after starting tamoxifen citrate and generally subside rapidly. In patients treated with tamoxifen citrate for metastatic breast cancer, the most frequent adverse reaction to tamoxifen citrate is hot flashes. Other adverse reactions which are seen infrequently are hypercalcemia, peripheral edema, distaste for food, pruritus vulvae, depression, dizziness, light-headedness, headache, hair thinning and/or partial hair loss, and vaginal dryness. Premenopausal Women: The following table summarizes the incidence of adverse reactions reported at a frequency of 2% or greater from clinical trials (Ingle, Pritchard, Buchanan) which compared tamoxifen citrate therapy to ovarian ablation in premenopausal patients with metastatic breast cancer. *Some women had more than one adverse reaction. TAMOXIFEN CITRATE All Effects % of Women OVARIAN ABLATION All Effects % of Women Adverse Reactions* n=104 n=100 Flush 33 46 Amenorrhea 16 69 Altered Menses 13 5 Oligomenorrhea 9 1 Bone Pain 6 6 Menstrual Disorder 6 4 Nausea 5 4 Cough/Coughing 4 1 Edema 4 1 Fatigue 4 1 Musculoskeletal Pain 3 0 Pain 3 4 Ovarian Cyst(s) 3 2 Depression 2 2 Abdominal Cramps 1 2 Anorexia 1 2 Male Breast Cancer: Tamoxifen citrate is well tolerated in males with breast cancer. […]
Interactions with other medicines
Drug Interactions: When tamoxifen citrate is used in combination with coumarin-type anticoagulants, a significant increase in anticoagulant effect may occur. Where such coadministration exists, careful monitoring of the patient’s prothrombin time is recommended. In the NSABP P-1 trial, women who required coumarin-type anticoagulants for any reason were ineligible for participation in the trial (See CONTRAINDICATIONS ). There is an increased risk of thromboembolic events occurring when cytotoxic agents are used in combination with tamoxifen citrate. Tamoxifen reduced letrozole plasma concentrations by 37%. The effect of tamoxifen on metabolism and excretion of other antineoplastic drugs, such as cyclophosphamide and other drugs that require mixed function oxidases for activation, is not known. Tamoxifen and N-desmethyl tamoxifen plasma concentrations have been shown to be reduced when coadministered with rifampin or aminoglutethimide. Induction of CYP3A4-mediated metabolism is considered to be the mechanism by which these reductions occur; other CYP3A4 inducing agents have not been studied to confirm this effect. One patient receiving tamoxifen citrate with concomitant phenobarbital exhibited a steady state serum level of tamoxifen lower than that observed for other patients (i.e., 26 ng/mL vs. mean value of 122 ng/mL). However, the clinical significance of this finding is not known. Rifampin induced the metabolism of tamoxifen and significantly reduced the plasma concentrations of tamoxifen in 10 patients. Aminoglutethimide reduces tamoxifen and N-desmethyl tamoxifen plasma concentrations. Medroxyprogesterone reduces plasma concentrations of N-desmethyl, but not tamoxifen. Concomitant bromocriptine therapy has been shown to elevate serum tamoxifen and N-desmethyl tamoxifen. Based on clinical and pharmacokinetic results from the anastrozole adjuvant trial, tamoxifen citrate should not be administered with anastrozole (see CLINICAL PHARMACOLOGY – Drug- Drug Interactions section).
If too much is taken
OVERDOSAGE Signs observed at the highest doses following studies to determine LD 50 in animals were respiratory difficulties and convulsions. Acute overdosage in humans has not been reported. In a study of advanced metastatic cancer patients which specifically determined the maximum tolerated dose of tamoxifen citrate in evaluating the use of very high doses to reverse multidrug resistance, acute neurotoxicity manifested by tremor, hyperreflexia, unsteady gait and dizziness were noted. These symptoms occurred within 3 to 5 days of beginning tamoxifen citrate and cleared within 2 to 5 days after stopping therapy. No permanent neurologic toxicity was noted. One patient experienced a seizure several days after tamoxifen citrate was discontinued and neurotoxic symptoms had resolved. The causal relationship of the seizure to tamoxifen citrate therapy is unknown. Doses given in these patients were all greater than 400 mg/m 2 loading dose, followed by maintenance doses of 150 mg/m 2 of tamoxifen citrate given twice a day. In the same study, prolongation of the QT interval on the electrocardiogram was noted when patients were given doses higher than 250 mg/m 2 loading dose, followed by maintenance doses of 80 mg/m 2 of tamoxifen citrate given twice a day. For a woman with a body surface area of 1.5 m 2 the minimal loading dose and maintenance doses given at which neurological symptoms and QT changes occurred were at least 6 fold higher in respect to the maximum recommended dose. No specific treatment for overdosage is known; treatment must be symptomatic.
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This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 30 April 2026. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.