The typical tamoxifen dosage for adults is 20 mg by mouth once daily. Some people may need a higher dosage of 40 mg daily, which is usually taken as 20 mg twice a day. Includes Tamoxifen indications, dosage/administration, pharmacology, mechanism/onset/duration of action, half-life, dosage forms, interactions, warnings, adverse reactions, off-label uses and more. The FDA-approved dosage for tamoxifen in breast cancer treatment is 20 mg daily, which can be given as a single dose or divided into two 10 mg doses (morning and evening) 1 Medscape - Breast cancer dosing for Soltamox (tamoxifen), frequency-based adverse effects, comprehensive interactions, contraindications, pregnancy & lactation schedules, and cost information. Detailed Tamoxifen dosage information for adults and children. Includes dosages for Breast Cancer, Breast Cancer - Adjuvant, Precocious Puberty and more; plus renal, liver and dialysis adjustments. Tamoxifen is typically taken once a day, but that can vary based on your health and risk factors. There are two common dosage options: 20 milligrams (mg) daily for five years or 10 mg every other day for three years. The recommended dose of tamoxifen for adult patients with a history of breast cancer is 20 mg orally once daily for 5 years. 1, 2, 3, 4. Do not prescribe tamoxifen to patients with: 2, 3, 7. The most significant error is dose escalation beyond 20 mg daily in an attempt to improve efficacy. Tamoxifen blocks the actions of estrogen in breast tissue and is used to treat estrogen receptor-positive breast cancer in adults and to lower the risk of breast cancer in women with DCIS or at high risk. Learn about side effects, interactions, and indications. Tamoxifen Dosage and Administration Adult Treatment: 20–40mg/day; give doses 20mg in divided doses (AM and PM). Reduction of incidence in high-risk women or DCIS: 20mg once daily for 5 years. TAMOXIFEN (ta MOX i fen) prevents and treats breast cancer. It works by blocking the hormone estrogen in breast tissue, which prevents breast cancer cells from spreading or growing.