Generic Tamoxifen

Common use
Tamoxifen is a selective estrogen receptor modulator (SERM) used primarily to treat and prevent breast cancer. It works by blocking estrogen receptors in breast tissue, slowing or stopping the growth of hormone-receptor-positive tumors. Tamoxifen is also prescribed to reduce the risk of breast cancer in high-risk patients. It is effective in both premenopausal and postmenopausal women.

Dosage and direction
Tamoxifen is usually taken once daily, with or without food, at a dose of 20 mg, though dosages may vary depending on the condition being treated. It should be taken at the same time each day for consistency. Swallow the tablet whole with water. Treatment duration can range from 5 to 10 years based on the individual case and doctor’s recommendation.

Precautions
Before starting tamoxifen, inform your doctor if you have a history of blood clots, stroke, or liver disease. Regular monitoring is required, including breast exams, mammograms, and gynecologic evaluations. The medication can cause changes in the uterine lining and increase the risk of endometrial cancer. Avoid pregnancy during treatment and for a time after stopping, as tamoxifen can harm a developing fetus.

Contraindications
Tamoxifen is contraindicated in individuals with known hypersensitivity to the drug or its components. It should not be used during pregnancy or while breastfeeding. Patients with a history of deep vein thrombosis or pulmonary embolism should avoid tamoxifen unless deemed essential by a physician. Use caution in those with pre-existing endometrial abnormalities.

Possible side effect
Common side effects include hot flashes, vaginal discharge, irregular menstruation, and fatigue. Less common but serious effects include blood clots, stroke, and endometrial cancer. Some patients may experience mood changes or visual disturbances. Seek medical attention if you notice leg swelling, chest pain, or unusual bleeding.

Drug interaction
Tamoxifen may interact with certain antidepressants (such as fluoxetine and paroxetine), which can reduce its effectiveness. It may also interact with blood thinners like warfarin, increasing bleeding risk. Inform your doctor about all medications, supplements, and herbal products you are taking. Dose adjustments or alternative therapies may be required.

Missed dose
If you miss a dose, take it as soon as possible. If it is near the time for your next dose, skip the missed dose and resume your regular schedule. Do not double up on doses. Maintaining a consistent daily routine enhances the effectiveness of treatment.

Overdose
Symptoms of overdose may include tremors, dizziness, and difficulty walking. Seek emergency medical attention if overdose is suspected. Treatment is supportive, and no specific antidote exists. Monitor for signs of toxicity and complications.

Storage
Store tamoxifen at room temperature, away from moisture, heat, and light. Keep the tablets in their original packaging. Do not use after the expiration date. Keep out of reach of children.

Disclaimer

We provide only general information about medications which does not cover all directions, possible drug integrations, or precautions. Information at the site cannot be used for self-treatment and self-diagnosis. Any specific instructions for a particular patient should be agreed with your health care adviser or doctor in charge of the case. We disclaim reliability of this information and mistakes it could contain. We are not responsible for any direct, indirect, special or other indirect damage as a result of any use of the information on this site and also for consequences of self-treatment.

Clinical Verification

Last Clinically Updated: August 15, 2026

Written By

Dr. Elena Vance, PharmD

Clinical Specialist in Neuropharmacology

Fact Checked By

Marcus Thorne, MS

Biomedical Data & FDA Label Verification

Medically Reviewed By

Dr. Arthur Campbell, MD

Board-Certified Psychiatrist (ABPN)