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tamoxifen (Rx)Brand and Other Names:Soltamox

 
 
 

Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablet (generic)

  • 10mg
  • 20mg

oral solution

  • 10mg/5mL (Soltamox)
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Breast Cancer Treatment

20-40 mg/day PO; doses >20mg/day should be divided BID (ie, morning and evening)

Although the FDA has approved a dosage range of 20-40 mg/day, clinical benefit for doses >20 mg/day has not been demonstrated

Continue with adjuvant therapy for at least 5 years

For women with ER-positive disease, continuing tamoxifen to 10 years rather than stopping at 5 years produces a further reduction in recurrence and mortality, particularly after year 10 (ATLAS trial, Lancet 2013;381:805-816; aTTom trial; ASCO Annual Meeting 2013;31:5)

Treatment indications

  • Treatment of metastatic breast cancer in women and men; in premenopausal women, alternative to oophorectomy or ovarian irradiation; estrogen receptor positive tumors more likely to benefit
  • Adjuvant treatment of node-positive breast cancer in postmenopausal women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation; most benefit in the subgroup with 4 or more positive axillary nodes
  • Adjuvant treatment of axillary node-negative breast cancer in women following total mastectomy or segmental mastectomy, axillary dissection, and breast irradiation
  • Reduces occurrence of contralateral breast cancer in patients receiving adjuvant treatment

Ductal Carcinoma in Situ

Indicated in women with ductal carcinoma in situ following breast surgery and radiation to reduce the risk of invasive breast cancer

20 mg PO qDay for 5 years

Breast Cancer Prevention

Indicated to reduce the incidence of breast cancer in women at high risk for breast cancer; high risk is defined as women aged ≥35 years with a 5-year predicted risk of breast cancer ≥1.67% (calculated by the Gail Model)

20 mg PO qDay for 5 years

Data are limited for use >5 yr in the risk-reduction setting (NCCN guidelines)

Ovulation Induction (Off-label)

5-40 mg PO q12hr for 4 days

Mastalgia (Off-label)

10 mg PO qDay for 4 months

Other Indications & Uses

Gynecomastia

Safety and efficacy not established

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Interactions

Interaction Checker

tamoxifen and

No Results

     
     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Hot flashes (64%)

            Vaginal discharge (30%)

            Amenorrhea (16%)

            Menstrual changes (13%)

            1-10%

            Oligomenorrhea (9%)

            Cataracts (8%)

            Bone pain (6%)

            Nausea (5%)

            Cough (4%)

            Edema (4%)

            Fatigue (4%)

            Musculoskeletal pain (3%)

            Ovarian cyst (3%)

            Depression (2%)

            Abdominal cramps (1%)

            Anorexia (1%)

            <1%

            Angioedema

            Corneal changes

            Loss of libido

            Endometrial cancer

            Pancreatitis

            Retinal vein thrombosis

            Stroke

            Uterine fibroids

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            Warnings

            Black Box Warnings

            For women with ductal carcinoma in situ (DCIS) and women at high risk for breast cancer:

            Uterine malignancies, stroke, and pulmonary embolism reported with use in risk-reduction setting (women with ductal carcinoma in situ and women at high risk for breast cancer).

            Contraindications

            Hypersensitivity

            Pregnancy

            Undiagnosed vaginal bleeding

            History of thromboembolism (prevention, DCIS)

            Coumarin anticoagulation (prevention, DCIS)

            Cautions

            History of thromboembolism (CA treatment); tamoxifen significantly increases risk of venous thromboembolism

            Coumarin anticoagulation (CA treatment)

            CYP2D6 polymorphism-CYP2D6 converts tamoxifen to active metabolite endoxifen; lowered CYP2D6 activity or concomitant CYP2D6 inhibitors may reduce tamoxifen efficacy

            Bone metastases

            Thrombocytopenia

            Cholestasis, fatty liver, hepatic necrosis, and hepatitis reported

            Leukopenia

            Postmarketing cases of hyperlipidemia reported

            Decreased visual acuity, corneal changes, retinal vein thrombosis

            Flushing and increased bone pain and/or tumor pain sometimes associated with good tumor response

            Chronic use for prevention may result in increased risk of stroke, pulmonary embolism, endometrial cancer, uterine sarcoma, cataract

            Avoid pregnancy

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            Pregnancy & Lactation

            Pregnancy Category: D

            Lactation: not known if excreted in breast milk, do not nurse

            Pregnancy Categories

            A:Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B:May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C:Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D:Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X:Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA:Information not available.

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            Pharmacology

            Mechanism of Action

            Selective estrogen receptor modulator: nonsteroid with potent antiestrogenic effects in breast (but may be estrogen agonist in uterus); has cytostatic effect rather than cytocidal effects (cells accumulate in Go and G1 phase of the cell cycle)

            Pharmacokinetics

            Half-Life: 7-14 hr

            Peak Plasma Time: 3-6 hr

            Protein binding: 99%

            Peak Plasma Concentration: 40 ng/mL

            Metabolism: by hepatic P450 enzyme CYP2C9,  CYP2D6, CYP3A4

            Metabolites: N-desmethyl tamoxifen, endoxifen

            Excretion: Feces (65%), urine (9%)

            Pharmacogenomics

            Metabolized via CYP2D6 into endoxifen (4-OH-N-desmethyl-tamoxifen), its primary active metabolite

            Lowered CYP2D6 activity or concomitant CYP2D6 inhibitors may reduce tamoxifen efficacy

            Poor CYP2D6 metabolizers are defined as those with *4/*4 alleles

            On October 18, 2006, the Pharmaceutical Science Clinical Pharmacology Subcommittee of the FDA recommended including information on CYP2D6 genotypes and their potential effect on patient outcomes in the label for tamoxifen, but they did not come to consensus on whether testing should be recommended or considered optional

            Subsequent to that recommendation, branded tamoxifen (Nolvadex) was discontinued and no further guidance was given by FDA on whether to amend the label for generic tamoxifen

            Recent data presented at the 2010 San Antonio Breast Cancer Symposium found the CYP2D6 allele status had no effect on any outcomes, including disease recurrence, distant recurrence, and overall survival

            Further research will help elucidate the potential effect of strong CYP2D6 inhibitors, such as SSRIs, on tamoxifen metabolism, but there is no evidence to suggest that the use of such medications should influence the use of tamoxifen

            Therefore, based on the data available to date, routine testing for CYP2D6 variants is not recommended

            CYP2C19 heterozygous *2 carriership may be a predictive factor for patients with breast cancer using tamoxifen; this factor was associated with a longer survival among tamoxifen users in a recent study (Pharmacogenomics. 2010;11[10]:1367-75)

            Genetic testing laboratories

            • The Roche Cytochrome AmpliChip P450 2D6/2C19 Genotyping and Phenotyping Assay can be used to identify 26 different alleles of CYP2D6, including *4
            • The following companies offer testing for CYP2D6 variants
            • DxS (http://www.dxsdiagnostics.com/)
            • LabCorp (http://www.labcorp.com/)
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            Images

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            Formulary

            FormularyPatient Discounts

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            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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