Tamoxifen
NOLVADEX
What it isSelective estrogen receptor modulator; hormone receptor-positive breast cancer at any age.
Why this oneIt works before menopause, which aromatase inhibitors do not, and it protects bone in postmenopausal women.
What limits itIt requires CYP2D6 activation to endoxifen, so strong inhibitors such as fluoxetine and paroxetine blunt it. Endometrial cancer and thromboembolism.
FDA-approved for
- breast cancer (1977)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Breast cancer (treatment/adjuvant) | Adults | 20 mg QD | 20 mg QD (20-40 mg/day) | 40 mg/day (BID if >20 mg) |
| Ductal carcinoma in situ (DCIS) | Adults | 20 mg QD × 5 yr | 20 mg QD | 20 mg QD |
| Breast cancer risk reduction (high-risk women) | Adults | 20 mg QD × 5 yr | 20 mg QD | 20 mg QD |
Renal Undefined
Hepatic Undefined
Instructions
- Doses >20 mg/day given in divided doses (morning and evening)
- Adjuvant therapy typically 5 years; no added benefit beyond 5 years
Contraindications
- Concomitant coumarin-type anticoagulant therapy (risk-reduction / DCIS use)
- History of deep vein thrombosis or pulmonary embolus (risk-reduction / DCIS use)
Cautions
- Uterine malignancies (endometrial carcinoma, uterine sarcoma)
- Thromboembolic events — stroke, pulmonary embolism, DVT
- Effects on the eye (cataracts, retinopathy); hypercalcemia; liver effects
- Embryo-fetal toxicity
Adverse reactions
- Hot flashes
- Vaginal discharge/bleeding
- Menstrual irregularity
- Nausea
- Fluid retention/edema
- Tumor/bone pain or disease flare
- Increased triglycerides
Pregnancy Can cause fetal harm (Category D); teratogenic — avoid in pregnancy
Lactation Undefined
⚠ BOXED WARNING
- Uterine malignancies, stroke and pulmonary embolism in risk-reduction settings
Cost, est. cash$10–$1,000/month
Generic entry2003
Classes and tags
Clinical profile
Legacy pregnancy categoryMultiple / indication-, trimester- or formulation-dependent
Defining liabilityThrombotic, metabolic, hepatic, skeletal or reproductive toxicity varies by hormonal target.
Active metabolites
Mechanism of action: Tamoxifen ballicule
Open Tamoxifen in the interactive console ↗
Memory aids: mascots and interaction avatars
bowling ball → CYP2D6 prodrug
