Tamoxifen: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing

Uses

What is tamoxifen used for?

Tamoxifen is commonly used to treat certain types of breast cancer. It is also used to lower your risk of invasive breast cancer and keep some breast cancers from coming back.

Tamoxifen may also be used for other conditions as determined by your healthcare provider.

How does tamoxifen work (mechanism of action)?

Tamoxifen acts like estrogen in some tissues and blocks estrogen activity in other tissues. It binds to estrogen receptors blocking growth of ER-positive breast tissue.

How is tamoxifen supplied (dosage forms)?

Brands and other names

Nolvadex
Soltamox

Dosage forms and strengths

20 mg/10 mL oral solution
10 mg, 20 mg oral tablets

How should I store tamoxifen?

Oral Tablets. Tamoxifen tablets should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Oral Solution. Liquid tamoxifen should be stored in the original container to protect it from light, at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place. It should not be stored in the refrigerator or the freezer.

Side Effects

What are the most common side effects of tamoxifen?

The most common side effects of tamoxifen are listed below. Tell your healthcare provider if you have any of these side effects that bother you.

Hot flashes
Changes in mood
Vaginal discharge or bleeding
Nausea
Fluid retention

There may be other side effects of tamoxifen that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of tamoxifen?

While less common, the most serious side effects of tamoxifen are described below, along with what to do if they happen.

Severe Allergic Reactions. Tamoxifen may cause allergic reactions, which can be serious. Stop taking tamoxifen and get help right away if you have any of the following symptoms of a serious allergic reaction.

Breathing problems or wheezing
Racing heart
Fever or general ill feeling
Swollen lymph nodes
Swelling of the face, lips, mouth, tongue, or throat
Trouble swallowing or throat tightness
Itching, skin rash, or pale red bumps on the skin called hives
Nausea or vomiting
Dizziness, feeling lightheaded, or fainting
Stomach cramps
Joint pain

Uterine Cancer. You may be at higher risk for cancer of the uterus (womb) or cancer in the lining of your uterus (endometrial cancer) if you take or have taken tamoxifen. Call your healthcare provider right away if you have any abnormal vaginal bleeding, discharge, or pelvic pain or pressure.

Blood Clots. Tamoxifen may cause blood clots in your arteries or veins and could cause a stroke, heart attack, or venous thromboembolism, including a blood clot in the lungs (pulmonary embolism) or deep venous thrombosis (DVT). Stop taking tamoxifen and get emergency help if you have any of the following signs of blood clots.

Chest pain or pressure
Fast or abnormal heartbeat
Trouble breathing
Pain in your back, jaw, throat, or arm
Sweating, upset stomach, vomiting, or dizziness
Sudden weakness on one side of your body
Sudden and severe headache
Slurred speech or trouble understanding speech
Pain, swelling, or tenderness in your arm or leg
Vision loss
Bulging eyes
Double vision

Liver Damage. Liver damage, also called hepatotoxicity, and sometimes liver cancer can happen when taking tamoxifen. Call your healthcare provider right away if you have any of the following symptoms of liver damage.

Nausea or vomiting
Stomach or belly pain
Fever
Weakness or unusual tiredness
Itching
Loss of appetite
Light-colored poop
Dark-colored urine (pee)
Your skin or the whites of your eyes turning yellowish in color (also called jaundice)

High Calcium Levels (Hypercalcemia). If you have breast cancer and it has spread to your bones, tamoxifen may cause high levels of calcium in your blood, which is known as hypercalcemia. Hypercalcemia can lead to serious problems with your kidneys, heart, or bones. Keep all healthcare appointments, including lab appointments to check your calcium levels, while taking tamoxifen.

Blood Disorders. Tamoxifen can cause low red blood cell levels (anemia), low white blood cell levels (leukopenia), or low platelet levels (thrombocytopenia). Keep all healthcare appointments, including lab appointments to check your blood cell levels, while taking tamoxifen.

Eye Problems. Tamoxifen can increase your chance of developing cataracts, needing cataract surgery, or other eye problems. Tell your healthcare provider if you notice eye symptoms, changes in your vision, or if things start to seem blurry.

Warnings & Precautions

Who should not use tamoxifen?

Allergies to Ingredients. People who are allergic to any of the following should not take tamoxifen.

Tamoxifen
Soltamox
Nolvadex
Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific tamoxifen products they stock.

Ductal Carcinoma in Situ (DCIS). If you have cancer in your milk ducts and either need to take warfarin or have had a blood clot in your veins or in your lungs, you should not take tamoxifen.

High Risk of Breast Cancer. If you have a higher than usual risk of developing breast cancer and either need to take warfarin or have had a blood clot in your veins or in your lungs, you should not take tamoxifen.

What should I know about tamoxifen before using it?

Do not take tamoxifen unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share tamoxifen with other people, even if they have the same condition as you. It may harm them.

Get regular pelvic exams (female exams), breast exams, and mammograms (x-ray to look closely at breast tissue) while taking tamoxifen.

Keep tamoxifen out of the reach of children.

If you take liquid tamoxifen, use the dosing cup that is provided with it to measure your doses. Once the bottle has been opened it is only good for three months. Write the date on the bottle the day you open it to help you keep track of this. Throw away any tamoxifen that is left in the bottle after 3 months.

Do not cut, chew, or break tamoxifen tablets. They should be swallowed whole.

You should perform monthly self-breast exams and have regular pelvic exams (female exam), breast exams (done by a healthcare provider) and mammograms (x-ray to look closely at breast tissue) before taking tamoxifen and during treatment with it.

What should I tell my healthcare provider before using tamoxifen?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are taking. This will help them determine if tamoxifen is right for you.

In particular, make sure that you discuss any of the following.

Other Medicines and Supplements. Tamoxifen may interact with other medicines and supplements. Before taking tamoxifen, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are taking. See the Interactions section for more details.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

No period, irregular periods, or unusual vaginal bleeding
Uterus problems, including cancer
Blood clots in your veins or lungs
Stroke

Pregnancy. You should use effective birth control while taking tamoxifen. Your healthcare provider may check to make sure you are not pregnant before you start taking tamoxifen. Tamoxifen may cause harm to an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. It is not known if tamoxifen passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should stop breastfeeding or stop tamoxifen.

Interactions

Does tamoxifen interact with foods or drinks?

There are no known interactions between tamoxifen and foods or drinks.

It is unknown if drinking alcohol will affect tamoxifen. However, the risk of hot flashes may be increased if you drink alcohol while taking tamoxifen because alcohol can trigger hot flashes.

Does tamoxifen interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are taking.

In particular, make sure that you discuss if you are taking any of the following before taking tamoxifen.

Warfarin, which is a blood thinner
Anastrozole (Arimidex) or letrozole (Femara), which is a medicine used to treat breast cancer
Rifampin, which is a medicine commonly used to treat an infection called tuberculosis

Some other medicines may alter the blood levels of tamoxifen. Tell your healthcare provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with tamoxifen. Always check with your healthcare provider.

Does Tamoxifen interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much tamoxifen?

If you or someone else has taken too much tamoxifen, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of tamoxifen?

If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Do not take double or extra doses.