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Pharmacologic class: Nonsteroidal antiestrogen
Therapeutic class: Antineoplastic
Pregnancy risk category D
FDA Box Warning
For women with ductal carcinoma in situ or high risk of breast cancer, serious and life-threatening events associated with drug use in riskreduction setting include stroke, pulmonary embolism, and uterine cancer. Some of these events were fatal. Discuss potential benefits versus potential risks of these events with these patients. In women already diagnosed with breast cancer, drug's benefits outweigh risks.
Competes with estrogen receptors in tumor cells for binding to target tissues (such as breast); reduces DNA synthesis and estrogen response
Oral solution: 10 mg/5 ml
Tablets: 10 mg, 20 mg
Tablets (enteric-coated): 20 mg
Indications and dosages
➣ Adjunctive treatment of breast cancer
Adults: 20 to 40 mg P.O. daily for 5 years. Daily dosages of 20 mg may be taken as a single dose; daily dosages above 20 mg should be divided and taken b.i.d. (morning and evening).
➣ To reduce breast cancer incidence in high-risk women; treatment of ductal carcinoma in situ
Adults: 20 mg P.O. daily for 5 years
• Ovulation stimulation
• Hypersensitivity to drug
• Concurrent warfarin use
• Women with a history of deep-vein thrombosis or pulmonary embolism
• Pregnancy or breastfeeding
Use cautiously in:
• decreased bone marrow reserve, leukopenia, thrombocytopenia, cataracts, hyperlipidemia
• females of childbearing age.
• Don't break or crush enteric-coated tablets.
• Know that drug is indicated for reducing breast cancer risk only in high-risk women, defined as those older than age 35 who have at least a 1.67% chance of developing breast cancer over 5 years.
CNS: confusion, depression, headache, weakness, fatigue, light-headedness
CV: chest pain, deep-vein thrombosis
EENT: blurred vision, ocular lesion, retinopathy, corneal opacity
GI: nausea, vomiting, abdominal cramps, anorexia
GU: vaginal bleeding, discharge, or dryness; irregular menses; amenorrhea; oligomenorrhea; ovarian cyst; pruritus vulvae; endometrial or uterine cancer
Hematologic: leukopenia, thrombocytopenia
Metabolic: hypercalcemia, fluid retention
Musculoskeletal: bone pain
Respiratory: cough, pulmonary embolism
Skin: skin changes, hair thinning or partial hair loss
Other: altered taste, weight loss, tumor flare, tumor pain, hot flashes, edema
Drug-drug. Aminoglutethimide, estrogens: decreased tamoxifen effects
Antineoplastics: increased risk of thromboembolic events
Bromocriptine: increased tamoxifen blood level
Warfarin: increased anticoagulant effect
Drug-diagnostic tests. Aspartate aminotransferase, bilirubin, calcium, creatinine, hepatic enzymes: increased levels
Platelets, white blood cells: decreased counts
• Monitor lipid panel, calcium level, mammography results, and gynecologic exam results.
Watch for signs and symptoms of thromboembolic events, including cerebrovascular accident and pulmonary embolism.
• Monitor menstrual cycle pattern for changes that may signal endometrial or uterine cancer.
• Tell patient to swallow enteric-coated tablets whole without breaking or crushing.
Instruct patient to immediately report leg or calf pain, swelling, or tenderness; unexpected shortness of breath; sudden chest pain; coughing up blood; new breast lumps; vaginal bleeding; menstrual irregularities; changes in vaginal discharge; pelvic pain or pressure; and vision changes.
• Inform patient that increase in bone or tumor pain usually means drug will be effective. Advise her to discuss pain management with prescriber.
• Stress importance of undergoing regular blood tests, mammograms, and gynecologic exams to identify early signs of serious adverse reactions.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs and tests mentioned above.
ta·mox·i·fen cit·rate(tă-mok'sĭ-fen sit'rāt),
Tamoxifen belongs to a class of synthetic agents known as selective estrogen receptor modulators (SERMs). By competing with naturally occurring estrogen for binding sites on tissue cells, tamoxifen inhibits the stimulant effect of estrogen on breast cancers. Tumors that have been shown by biochemical assay to be rich in estrogen receptors are most likely to respond to treatment. Since 1985, tamoxifen has been used to delay or prevent relapse in patients who have undergone surgery or irradiation for breast cancer. The drug has been found effective in reducing the risk of cancer recurrence or disease progression in women with or without axillary node metastasis. In women with extensive disease, tamoxifen therapy has been as effective as oophorectomy in retarding progression. Clinical trials of tamoxifen as a preventive agent in women at high risk of breast cancer have yielded conflicting results; current opinion is against using tamoxifen in women at low or normal risk of breast cancer because of side effects. Genomic analysis of healthy women who developed breast cancer while taking tamoxifen showed that tamoxifen reduced breast cancer incidence in women with the BRCA2 mutation, but not in those with the BRCA1 mutation. Women taking tamoxifen are at increased risk of endometrial carcinoma, stroke, deep venous thrombosis, pulmonary embolism, and cataracts. The danger of these adverse consequences is greatest in women older than 50. Long-term use of the drug is associated with recurrent vaginal candidosis. It is contraindicated during pregnancy because of the risk of fetal harm.