Tamoxifen Citrate

tamoxifen citrate (ta mox' i fen) Apo-Tamox (CAN), Nolvadex, Novo-Tamoxifen (CAN), Tamofen (CAN), Tamone (CAN) Pregnancy Category D Drug class

Antiestrogen Therapeutic actions

Potent antiestrogenic effects: Competes with estrogen for binding sites in target tissues, such as the breast. Indications

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Treatment of metastatic breast cancer in women and men; in premenopausal women with metastatic breast cancer, tamoxifen is an alternative to oophorectomy or ovarian irradiation Treatment of node-positive breast cancer in postmenopausal women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation Treatment of axillary node-negative breast cancer in women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation Reduction in risk of invasive breast cancer in women with ductal carcinoma in situ (DCIS) following breast surgery and radiation Reduction in occurrence of contralateral breast cancer in patients receiving adjuvant tamoxifen therapy for breast cancer Reduction in incidence of breast cancer in women at high risk for breast cancer Unlabeled uses: Treatment of mastalgia; useful for decreasing size and pain of gynecomastia; treatment of McCune–Albright syndrome and precocious puberty in female patients 2–10 yr

Contraindications and cautions

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Contraindicated with allergy to tamoxifen, pregnancy, lactation, women who require concomitant coumarin-type anticoagulation therapy or in women with a history of DVT or PE. Use cautiously in women with a history of thromboembolic events.

Available forms

Tablets—10, 20 mg Dosages ADULTS

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Breast cancer: 20–40 mg/day PO for 5 yr. Dosages > 20 mg/day should be given in divided doses, morning and evening. Reduction in breast cancer incidence: 20 mg/day PO for 5 yr.

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DCIS: 20 mg/day PO for 5 yr.

Pharmacokinetics Route Oral

Onset Varies

Peak 4–7 hr

Metabolism: Hepatic; T1/2: 7–14 days Distribution: Crosses placenta; may enter breast milk Excretion: Feces Adverse effects

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CNS: Depression, light-headedness, dizziness, headache, corneal opacity, decreased visual acuity, retinopathy, stroke Dermatologic: Hot flashes, rash, Stevens-Johnson syndrome GI: Nausea, vomiting, food distaste, alterations in liver enzymes GU: Vaginal bleeding, vaginal discharge, menstrual irregularities, pruritus vulvae, endometrial cancer, uterine sarcoma Hematologic: Hypercalcemia, especially with bone metastases, thrombocytopenia, leukopenia, anemia, DVT Other: Peripheral edema; increased bone and tumor pain and local disease (initially seen with a good tumor response, usually subsides); cancer in animal studies, changes in LFTs, PE

Interactions

Drug-drug • Increased risk of bleeding with oral anticoagulants • Increased serum levels with bromocriptine • Increased risk of thromboembolic events if given with cytotoxic agents Drug-food • Decreased metabolism and risk of toxic effects if combined with grapefruit juice; avoid this combination Drug-lab test • Possible increase in calcium levels, T4 levels without hyperthyroidism Nursing considerations Assessment

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History: Allergy to tamoxifen; pregnancy, lactation, previous DVT or PE Physical: Skin lesions, color, turgor; pelvic exam; orientation, affect, reflexes; ophthalmologic exam; peripheral pulses, edema; liver function tests, CBC and differential, estrogen receptor evaluation of tumor cells

Interventions

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Administer bid, in the morning and the evening. Arrange for periodic blood counts.

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Arrange for initial ophthalmologic exam and periodic exams if visual changes occur. Counsel patient to use contraception while taking this drug; inform patient that serious fetal harm could occur. Decrease dosage if adverse effects become severe.

Teaching points

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For doses greater than 20 mg, take the drug twice a day, in the morning and evening. Do not drink grapefruit juice while using this drug. This drug can cause serious fetal harm and must not be taken during pregnancy. Contraceptive measures should be used. If you become pregnant or decide that you would like to become pregnant, consult with your health care provider immediately. Have regular gynecologic exams during therapy. These side effects may occur: Bone pain; hot flashes (staying in cool temperatures may help); nausea, vomiting (eat frequent small meals); weight gain; menstrual irregularities; dizziness, headache, light-headedness (use caution if driving or performing tasks that require alertness). Report marked weakness, sleepiness, mental confusion, pain or swelling of the legs, shortness of breath, blurred vision.

Adverse effects in Italic are most common; those in Bold are life-threatening.