Tamoxifen Citrate (3 brand names, 2 dosage forms, 1 route)
Available dosage forms: TABLET, SOLUTION.
Routes of administration: ORAL.
Brand Names
- NOLVADEX
- SOLTAMOX
- TAMOXIFEN CITRATE
Boxed Warning
WARNING - For Women with Ductal Carcinoma in Situ (DCIS) and Women at High Risk for Breast Cancer: Serious and life-threatening events associated with tamoxifen citrate in the risk reduction setting (women at high risk for cancer and women with DCIS) include uterine malignancies, stroke and pulmonary embolism. Incidence rates for these events were estimated from the NSABP P-1 trial (see CLINICAL PHARMACOLOGY-Clinical Studies – Reduction in Breast Cancer Incidence In High Risk Women ). Uterine malignancies consist of both endometrial adenocarcinoma (incidence rate per 1,000 women-years of 2.20 for tamoxifen citrate vs 0.71 for placebo) and uterine sarcoma (incidence rate per 1,000 women-years of 0.17 for tamoxifen citrate vs 0.4 for placebo)*. For stroke, the incidence rate per 1,000 women-years was 1.43 for tamoxifen citrate vs 1.00 for placebo**. For pulmonary embolism, the incidence rate per 1,000 women-years was 0.75 for tamoxifen citrate versus 0.25 for placebo**. Some of the strokes, pulmonary emboli, and uterine malignancies were fatal. Health care providers should discuss the potential benefits versus the potential risks of these serious events with women at high risk of breast cancer and women with DCIS considering tamoxifen citrate to reduce their risk of developing breast cancer. The benefits of tamoxifen citrate outweigh its risks in women already diagnosed with breast cancer. *Updated long-term follow-up data (median length of follow-up is 6.9 years) from NSABP P-1 study. See WARNINGS: Effects on the Uterus-Endometrial Cancer and Uterine Sarcoma . **See Table 3 under CLINICAL PHARMACOLOGY-Clinical Studies .
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 inc
Dosage and Administration
For patients with breast cancer, the recommended daily dose is 20 to 40 mg. Dosages greater than 20 mg per day should be given in divided doses (morning and evening). In three single agent adjuvant studies in women, one 10 mg tamoxifen citrate tablet was administered two (ECOG and NATO) or three (Toronto) times a day for two years. In the NSABP B-14 adjuvant study in women with node-negative breast cancer, one 10 mg tamoxifen citrate tablet was given twice a day for at least 5 years. Results of the B-14 study suggest that continuation of therapy beyond five years does not provide additional benefit (see CLINICAL PHARMACOLOGY ). In the EBCTCG 1995 overview, the reduction in recurrence and mortality was greater in those studies that used tamoxifen for about 5 years than in those that used tamoxifen for a shorter period of therapy. There was no indication that doses greater than 20 mg per day were more effective. Current data from clinical trials support 5 years of adjuvant tamoxifen citrate therapy for patients with breast cancer. Ductal Carcinoma in Situ (DCIS): The recommended dose is tamoxifen citrate 20 mg daily for 5 years. Reduction in Breast Cancer Incidence in High Risk Women: The recommended dose is tamoxifen citrate 20 mg daily for 5 years. There are no data to support the use of tamoxifen citrate other than for 5 years (See CLINICAL PHARMACOLOGY-Clinical Studies - Reduction in Breast Cancer Incidence in High Risk Women ).
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.
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 Breas
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).
Overdosage
Signs observed at the highest doses following studies to determine LD 50in 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 2loading dose, followed by maintenance doses of 150 mg/m 2of 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 2loading dose, followed by maintenance doses of 80 mg/m 2of tamoxifen citrate given twice a day. For a woman with a body surface area of 1.5 m 2the 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.