Tamoxifen

FDA Drug Information • Also known as: SOLTAMOX

Brand Names: SOLTAMOX
Route: ORAL
Product Type: HUMAN PRESCRIPTION DRUG

⚠ Boxed Warning (Black Box)

WARNING: UTERINE MALIGNANCIES and THROMBOEMBOLIC EVENTS Serious and life-threatening events from the use of SOLTAMOX include uterine malignancies, stroke, and pulmonary embolism [see Warnings and Precautions (5.1 , 5.2) ] . Fatal cases of each type of event have occurred. Incidence rates per 1000 women-years for these events were estimated from the National Surgical Adjuvant Breast and Bowel Project (NSABP) P-1 trial in women at high risk for breast cancer [see Clinical Studies (14.4) ] : Endometrial adenocarcinoma: 2.20 for tamoxifen vs. 0.71 for placebo Uterine sarcoma: 0.17 for tamoxifen vs. 0.04 for placebo Stroke: 1.43 for tamoxifen vs. 1.00 for placebo. Pulmonary embolism: 0.75 for tamoxifen versus 0.25 for placebo. Discuss the potential benefits of tamoxifen versus the potential risks of these serious events with women at high risk for breast cancer and women with ductal carcinoma in situ (DCIS) considering tamoxifen to reduce the risk of developing breast cancer [see Warnings and Precautions (5) ]. For most patients already diagnosed with breast cancer, the benefits of tamoxifen outweigh its risks. WARNING: UTERINE MALIGNANCIES and THROMBOEMBOLIC EVENTS See full prescribing information for complete boxed warning . Serious, life-threatening, and fatal events from use of tamoxifen include uterine malignancies, stroke, and pulmonary embolism. ( 5.1 , 5.2 ) Discuss risks and benefits of tamoxifen with women at high risk for breast cancer and women with ductal carcinoma in situ (DCIS) when considering tamoxifen use to reduce the risk of developing breast cancer. ( 5.1 , 5.2 ) For most patients already diagnosed with breast cancer, the benefits of tamoxifen outweigh its risks. ( 5.1 , 5.2 )

Description

11 DESCRIPTION SOLTAMOX (tamoxifen citrate) oral solution is for oral administration. Tamoxifen citrate is an estrogen agonist/antagonist. Chemically, tamoxifen 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 formula, empirical formula, and molecular weight are as follows: C 32 H 37 NO 8 M.W. 563.62 Tamoxifen citrate has a pKa′ of 8.85. The equilibrium solubility in water at 37°C is 0.5 mg/mL, and is 0.2 mg/mL in 0.02 N HCl at 37°C. Each 10 mL of SOLTAMOX oral solution contains 20 mg tamoxifen, equivalent to 30.4 mg tamoxifen citrate. The oral solution is a sugar-free, clear colorless liquid, with licorice and aniseed odor and taste supplied in a 150 mL bottle with a dosing cup. SOLTAMOX oral solution contains the following inactive ingredients: ethanol, glycerol, propylene glycol, sorbitol solution, licorice flavor, aniseed flavor, purified water. Chemical Structure

What Is Tamoxifen Used For?

1 INDICATIONS AND USAGE SOLTAMOX is an estrogen agonist/antagonist indicated: For treatment of adult patients with estrogen receptor-positive metastatic breast cancer ( 1.1 ) For adjuvant treatment of adult patients with early stage estrogen receptor- positive breast cancer ( 1.2 ) To reduce risk of invasive breast cancer following breast surgery and radiation in adult women with ductal carcinoma in situ (DCIS) ( 1.3 ) To reduce the incidence of breast cancer in adult women at high risk ( 1.4 ) 1.1 Metastatic Breast Cancer SOLTAMOX is indicated for the treatment of adult patients with estrogen receptor-positive metastatic breast cancer. 1.2 Adjuvant Treatment of Breast Cancer SOLTAMOX is indicated: for the adjuvant treatment of adult patients with early stage estrogen receptor-positive breast cancer to reduce the occurrence of contralateral breast cancer in adult patients when used as adjuvant therapy for the treatment of breast cancer. 1.3 Ductal Carcinoma in Situ In adult women with DCIS, following breast surgery and radiation, SOLTAMOX is indicated to reduce the risk of invasive breast cancer [see Boxed Warning and Clinical Studies (14.3) ] . 1.4 Reduction in Breast Cancer Incidence in Women at High Risk SOLTAMOX is indicated to reduce the incidence of breast cancer in adult women at high risk for breast cancer. [see Boxed Warning and Clinical Studies (14.4) ] .

Dosage and Administration

2 DOSAGE AND ADMINISTRATION Metastatic breast cancer: 20-40 mg per day. For doses greater than 20 mg per day, administer in divided doses (morning and evening). ( 2 ) Adjuvant treatment of breast cancer, DCIS, reduction of breast cancer incidence in women at high risk: 20 mg per day ( 2 ) Metastatic Breast Cancer For patients with breast cancer, the recommended daily dose of SOLTAMOX is 20 to 40 mg. Doses greater than 20 mg per day should be given in divided doses (morning and evening). Adjuvant Treatment of Breast Cancer For use in the adjuvant setting, the recommended dose of SOLTAMOX is 20 mg daily for 5-10 years [see Clinical Studies (14.2) ] . Doses greater than 20 mg daily yield no additional clinical benefit. Ductal Carcinoma in Situ For patients with DCIS, the recommended dose of SOLTAMOX is 20 mg daily for 5 years. Reduction in Breast Cancer Incidence in Women at High Risk In the risk reduction setting, the recommended dose of SOLTAMOX is 20 mg daily for 5 years .

Side Effects (Adverse Reactions)

6 ADVERSE REACTIONS The following serious adverse reactions are discussed below and elsewhere in the labeling: Uterine malignancies [see Boxed Warning , Warnings and Precautions (5.1) , and Clinical Studies (14.4) ] Thromboembolic events [see Boxed Warning , Warnings and Precautions (5.2) , and Clinical Studies (14.4) ] Embryo-Fetal Toxicity [see Warnings and Precautions (5.3) , and Use in Specific Populations (8.1 , 8.3) ] Liver cancer [see Warnings and Precautions (5.4) ] Most common adverse reactions: hot flashes, mood disturbances, vaginal discharge, vaginal bleeding, nausea, and fluid retention ( 6.1 ). To report SUSPECTED ADVERSE REACTIONS, contact Mayne Pharma at 1-844-825-8500 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. Adverse Reactions in Patients with Metastatic Breast Cancer In patients treated with tamoxifen for metastatic breast cancer, the most frequent adverse reaction was hot flashes. Other adverse reactions which were seen less commonly are hypercalcemia, peripheral edema, distaste for food, pruritus vulvae, depression, dizziness, lightheadedness, headache, hair thinning and/or partial hair loss, and vaginal dryness. Increased bone, tumor pain and local disease flare have occurred. Patients with soft tissue disease may have sudden increases in the size of preexisting lesions, sometimes associated with marked erythema within and surrounding the lesions and/or the development of new lesions. When they occurred, the bone pain or disease flares were seen shortly after starting tamoxifen and generally subsided rapidly. Premenopausal Women with Metastatic Breast Cancer Table 1 summarizes the incidence of adverse reactions reported at a frequency of 2% or greater from clinical trials that compared tamoxifen therapy to ovarian ablation in premenopausal patients with metastatic breast cancer. Table 1: Adverse Reactions (frequency ≥2% in either arm) from Trials Comparing Tamoxifen to Ovarian Ablation in Premenopausal Women with Metastatic Breast Cancer % of Women Tamoxifen N=104 Ovarian Ablation N=100 Adverse Reactions Some women had more than one adverse reaction. 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 Adverse Reactions in Adjuvant Breast Cancer In the NSABP B-14 study, women with axillary node-negative breast cancer were randomized to 5 years of tamoxifen 20 mg per day or placebo following primary surgery [see Clinical Studies (14.2) ]. Table 2 presents the most common adverse reactions (mean follow-up of approximately 6.9 years) that were more common on tamoxifen than placebo. Table 2: Most Common Adverse Reactions in Women with Axillary Node-Negative Breast Cancer (Study NSABP B-14) % of Women Tamoxifen N=1,422 Placebo N=1,437 Hot flashes 64 48 Fluid retention 32 30 Vaginal discharge 30 15 Nausea 26 24 Irregular menses 25 19 Weight loss (>5%) 23 18 Skin changes 19 15 Increased SGOT 5 3 Increased bilirubin 2 1 Increased creatinine 2 1 Thrombocytopenia Defined as a platelet count of < 100,000/mm 3 2 1 Thrombotic events Two of the tamoxifen-treated patients who had thrombotic events died. Deep vein thrombosis 0.8 0.2 Pulmonary embolism 0.5 0.2 Superficial phlebitis 0.4 0 In the Eastern Cooperative Oncology Group (ECOG) adjuvant breast cancer trial [see Clinical Studies (14.2) ] , tamoxifen or placebo was administered for 2 years to women following mastectomy. When compared to placebo, tamoxifen showed a higher incidence of hot flashes (19% vs. 8% for placebo). The incidence of all other adverse reactions...

Drug Interactions

7 DRUG INTERACTIONS Anastrozole and letrozole: Should not be used in combination with tamoxifen. ( 7.1 ) Warfarin: Do not use in patients taking tamoxifen for DCIS and for reduction in breast cancer incidence in women at high risk. ( 4 ) Closely monitor coagulation indices for increased anticoagulant effect when used with tamoxifen for metastatic breast cancer or as adjuvant therapy. ( 7.2 ) 7.1 Aromatase Inhibitors Anastrozole The combination of anastrozole and tamoxifen did not demonstrate any benefit when compared to tamoxifen alone and should be avoided in all patients [see Clinical Studies (14.2) ] . In the ATAC trial, coadministration of anastrozole and tamoxifen in breast cancer patients reduced the anastrozole plasma concentration by 27% compared to that achieved with anastrozole alone. The tamoxifen concentration was not altered [see Clinical Pharmacology (12.3) ]. Letrozole The concomitant use of letrozole with tamoxifen is not recommended because the efficacy of the combination in the adjuvant treatment of breast cancer has not been established. Tamoxifen reduced the plasma concentration of letrozole by 38% when these drugs were co-administered [see Clinical Pharmacology (12.3) ]. 7.2. Warfarin A marked increase in anticoagulant effect may occur when tamoxifen is used in combination with warfarin. Closely monitor coagulation indices in patients who are taking tamoxifen for either the treatment of metastatic breast cancer or as adjuvant therapy who require concomitant use of warfarin [see Contraindications (4) ] . 7.3 Inducers of CYP3A4 Strong CYP3A4 inducers should not be used with tamoxifen. Strong CYP3A4 inducers (e.g., rifampin) reduce tamoxifen AUC and C max [see Clinical Pharmacology (12.3) ] . 7.4 Strong Inhibitors of CYP2D6 The impact on the efficacy of tamoxifen with co-administration of strong CYP2D6 inhibitors (e.g., paroxetine) is not well established. Some studies have shown that the efficacy of tamoxifen may be reduced when the drugs are co-administered as a result of reduced levels of potent active metabolites of tamoxifen . However, other studies have failed to demonstrate such an effect [see Clinical Pharmacology (12.3) ] . 7.5 Drug-Laboratory Test Interactions There are postmarketing reports of T 4 elevations in postmenopausal patients taking tamoxifen that may be explained by increases in thyroid-binding globulin. These elevations were not accompanied by clinical hyperthyroidism. Variations in the karyopyknotic index on vaginal smears and various degrees of estrogen effect on Pap smears have been seen in postmenopausal patients taking tamoxifen.

Contraindications

4 CONTRAINDICATIONS SOLTAMOX is contraindicated in patients with known hypersensitivity (e.g., angioedema, serious skin reactions) to tamoxifen or any other SOLTAMOX ingredient [see Adverse Reactions (6.2) ] . SOLTAMOX is contraindicated in patients who require concomitant warfarin therapy or have a history of deep vein thrombosis or pulmonary embolus if the indication for treatment is either reduction of breast cancer incidence in high-risk patients or risk reduction of invasive breast cancer after treatment of DCIS [see Warnings and Precautions (5.2) and Drug Interactions (7.2) ]. Known hypersensitivity to tamoxifen or any other SOLTAMOX ingredient ( 4 ) In patients who require concomitant warfarin therapy or have a history of deep vein thrombosis or pulmonary embolus, if the indication for treatment is either reduction of breast cancer incidence in high-risk patients or risk reduction of invasive breast cancer after treatment of DCIS ( 4 )

Pregnancy and Breastfeeding

8.1 Pregnancy Risk Summary SOLTAMOX can cause fetal harm when administered to a pregnant woman . There are no adequate and well- controlled studies of tamoxifen in pregnant women. There are limited postmarketing reports of vaginal bleeding, spontaneous abortions, birth defects, and fetal deaths in pregnant women taking tamoxifen. In a primate model administration of tamoxifen at doses 2 times higher than the maximum recommended human dose resulted in spontaneous abortion. In rat and rabbit studies, doses of tamoxifen less than or equal to human doses resulted in increased embryotoxicity, abortions, and altered learning behaviors. Additionally, rodent models showed reproductive tract changes often associated with DES in offspring of both sexes [ see Data ]. Advise pregnant women of the potential risk to a fetus, including the potential long-term risk of a DES-like syndrome. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively. Data Animal Data In embryofetal development studies in rats using doses significantly below those used in humans (0.01 to 0.03 times the recommended human dose on a mg/m 2 basis), a lower incidence of embryo implantation and a higher incidence of fetal death or delayed in utero growth occurred, along with slower learning behavior in some rat pups when compared to historical controls. When pregnant rabbits received tamoxifen during organogenesis, abortion and premature delivery occurred at doses of greater than 0.125 mg/kg/day (about 0.05 times the daily maximum recommended human dose on a mg/m 2 basis). Although reversible nonteratogenic skeletal variations occurred in rat reproductive studies at doses less than or equal to the human dose, there were no teratogenic changes in either rats or rabbits. In pregnant...

Overdosage

10 OVERDOSAGE No specific treatment for SOLTAMOX overdosage is recommended, other than symptomatic treatment. In a study of advanced metastatic cancer patients to determine the maximum tolerated dose of tamoxifen that could reverse multidrug resistance, the following adverse events were observed: acute neurotoxicity manifested by tremor, hyperreflexia, unsteady gait, and dizziness. These symptoms occurred within 3 to 5 days of beginning tamoxifen 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 was discontinued and neurotoxic symptoms had resolved. The causal relationship of the seizure to tamoxifen therapy is unknown. Doses given in these patients were all greater than 400 mg/m 2 loading dose (at least 6-fold higher than the recommended dosage), followed by maintenance doses of 150 mg/m 2 of tamoxifen given twice a day (at least 6-fold higher than the recommended dosage). 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 (at least 6-fold higher than the recommended dose) , followed by maintenance doses of 80 mg/m 2 of tamoxifen given twice a day. For a woman with a body surface area of 1.5 m 2 , the minimal loading dose and maintenance doses at which neurological symptoms and QT changes occurred were at least 6-fold higher in respect to the maximum recommended dose. Signs observed at the highest doses following studies to determine LD 50 in animals were respiratory difficulties and convulsions.

How Supplied

16 HOW SUPPLIED/STORAGE AND HANDLING SOLTAMOX oral solution is a sugar-free, clear colorless liquid, with licorice and aniseed odor and taste. It is supplied in a 150 mL bottle with a dosing cup intended for the measurement of SOLTAMOX oral solution only. Each 10 mL of solution contains 20 mg tamoxifen, equivalent to 30.4 mg tamoxifen citrate. NDC# 51862- 682 -01 Store at room temperatures 20° to 25°C (68° - 77°F); excursions permitted between 15° to 30°C (59° - 86°F) [see USP Controlled Room Temperature]. DO NOT freeze or refrigerate. Store in original packaging in order to protect from light. Discard any unused portion after 3 months of first opening of the bottle.

About This Information

This drug information is sourced from FDA-approved labeling via the openFDA database. It is intended for educational and reference purposes only. This is not medical advice. Always consult your healthcare provider before making decisions about medication. Drug information may be updated by the FDA; check with your pharmacist for the most current information.

What are side effects?

Side effects are unwanted reactions that can occur when taking a medication. They range from mild (headache, nausea) to severe (allergic reactions, organ damage). Not everyone experiences side effects, and severity varies. Report any concerning side effects to your doctor.

What are drug interactions?

Drug interactions occur when a medication is affected by another drug, food, or supplement. Interactions can make medications less effective or cause dangerous side effects. Always tell your doctor about all medications and supplements you take.