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Thursday, February 10, 2011

tamoxifen citrate

Posted by Sampil 2:23 AM, under | No comments

tamoxifen citrate
(ta mox' i fen)
Apo-Tamox (CAN), Nolvadex, Novo-Tamoxifen (CAN), Tamofen (CAN)

Pregnancy Category D

Drug class
Antiestrogen
Antineoplastic

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

Indications
·        Treatment of metastatic breast cancer in women and men; in premenopausal women with metastatic breast cancer, tamoxifen is an alternative tooophorectomy 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; malignant carcinoid tumor, carcinoid syndrome

Contraindications and cautions
·        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
·        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.
·        DCIS: 20 mg/day PO for 5 yr.

Pharmacokinetics
Route
Onset
Peak
Oral
Varies
4–7 hr

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

Adverse effects
·        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
·        HematologicHypercalcemia, 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 LFTsPE

Interactions
·        Increased risk of bleeding with oral anticoagulants
·        Increased serum levels with bromocriptine
·        Increased risk of thromboembolic events if given with cytotoxic agents
·        Decreased metabolism and risk of toxic effects if combined with grapefruit juice; avoid this combination
·        Possible increase in calcium levels, T4 levels without hyperthyroidism

Nursing considerations
Assessment
·        History: Allergy to tamoxifen; pregnancy, lactation, previous DVT or PE
·        Physical: Skin lesions, color, turgor; pelvic examination; orientation, affect, reflexes; ophthalmologic examination; peripheral pulses, edema; LFTs, CBC and differential, estrogen receptor evaluation of tumor cells

Interventions
·        Administer bid, in the morning and the evening.
·        Arrange for periodic blood counts.
·        Arrange for initial ophthalmologic examination and periodic examinations 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
·        For doses greater than 20 milligrams, 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 you want to become pregnant, consult your health care provider immediately.
·        Have regular gynecologic examinations during therapy.
·        You may experience these side effects: Bone pain; hot flashes (staying in cool places 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.

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