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Tamoxifen

Brand names: Soltamox

Tamoxifen blocks estrogen in breast tissue. It treats and helps prevent hormone-sensitive breast cancer.

Brand namesSoltamox
Type of medicineHormone therapy for breast cancer (SERM)
Prescription?Prescription
ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.

Overview

It's often taken for 5 to 10 years after treatment.

What it's used for

  • Hormone-receptor-positive breast cancer
  • Lowering breast cancer risk in high-risk people
  • DCIS

How to take it

  • Take it once a day at the same time, with or without food.

Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.

Side effects

Common side effects

  • Hot flashes
  • Vaginal discharge or dryness
  • Irregular periods
  • Tiredness
Call 911Chest pain, sudden shortness of breath, or signs of a stroke
Call your provider todayPain or swelling in one leg
Call your provider todayVaginal bleeding after menopause, or pelvic pain or pressure (possible uterine cancer)
Call your provider todayVision changes

Warnings

  • Boxed warning: uterine cancer, stroke, and blood clots in the lungs.
  • Get regular gynecologic and eye exams.

Other medicines, foods, and alcohol

  • Paroxetine, fluoxetine, and bupropion can make it less effective.
  • It raises the effect of warfarin.

Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.

Pregnancy and breastfeeding

It can harm an unborn baby. Use non-hormonal birth control during treatment and for 2 months after.

Missed doses, overdose, and storage

If you miss a dose

Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.

If someone takes too much

Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.

Storing it

Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.

Conditions it's used for

Sources

Last updated 2026-11-13.