Tamoxifen: Uses, Dosing & Side Effects

Tamoxifen is a medication used to treat breast cancer that depends on estrogen for growth. It works by blocking the action of this hormone, preventing it from attaching to breast cancer cells and helping to stop tumor growth.

This medication is available in pharmacies and hospitals as 10 mg or 20 mg tablets, sold under the brand name Nolvadex or as the generic tamoxifen citrate.

Tamoxifen should always be used under the supervision of an oncologist, who will prescribe the correct dose and treatment duration based on each person’s specific condition.

Indications for use

Tamoxifen is indicated for the treatment of early-stage breast cancer that is estrogen receptor-positive or has an unknown receptor status.

It works by blocking estrogen from binding to cancer cells, which prevents the tumor from growing. Tamoxifen can be used regardless of age, menopausal status, or required dose.

This medication can also be prescribed for men with estrogen receptor-positive breast cancer.

Dosing instructions

Tamoxifen tablets should be taken orally with a small amount of water. The tablets must be swallowed whole, without breaking or chewing, and should be taken at the same time every day.

The usual recommended dose is 20 mg once daily, or 10 mg twice daily if preferred. In some cases, the dose may be increased to 40 mg per day, taken as 20 mg twice daily.

Treatment with tamoxifen generally lasts between 5 and 10 years and should always follow the oncologist’s instructions.

Missed dose

If you forget to take a dose of tamoxifen, take it as soon as you remember, as long as it’s within 12 hours of the missed dose. The next dose should then be taken at the usual time.

If more than 12 hours have passed since the missed dose, contact your doctor. You should not take two doses within a 12-hour period.

Side effects

The most common side effects that may occur during treatment with tamoxifen include:

• Nausea;

• Fluid retention or swollen ankles;

• Vaginal bleeding or discharge;

• Hot flashes;

• Mood changes or depression;

• Skin blistering, itching, or peeling;

• Fatigue.

Tamoxifen can also increase the risk of developing blood clots, pulmonary embolism, deep vein thrombosis (DVT), or stroke.

You should seek medical attention immediately if you experience symptoms such as sudden numbness or weakness, severe headache, slurred speech, vision or balance problems, chest pain, sudden cough, shortness of breath, dizziness, or pain, swelling, or warmth in one leg.

Contraindications for use

Tamoxifen should not be used by children, teenagers, people who are pregnant or breastfeeding, or anyone allergic to tamoxifen citrate or any of its ingredients.

Caution is advised when tamoxifen is used with anticoagulants such as warfarin, as it can increase the risk of bleeding and requires close monitoring. It should also not be taken with rifampin, which can reduce its effectiveness, or with certain antidepressants like paroxetine or fluoxetine that interfere with tamoxifen metabolism.

Tamoxifen should not be taken at the same time as aromatase inhibitors such as anastrozole, letrozole, or exemestane.

Always tell your doctor or pharmacist about all medications, herbal products, or supplements you are using to prevent interactions that could either increase or reduce the effect of tamoxifen.