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What is tamoxifen

Tamoxifen blocks the actions of the hormone estrogen. Certain types of breast cancer require estrogen to grow.

Tamoxifen is used to treat and prevent some types of breast cancer that require estrogen to grow.

Tamoxifen may also be used for purposes other than those listed in this medication guide.

General medical information about tamoxifen

Treatment with tamoxifen may increase the risk of certain uterine cancers, stroke, and pulmonary embolism (blood clot in the lung), which may be fatal. You should discuss with your doctor the risks and benefits associated with the use of tamoxifen.

What you should find out before taking tamoxifen

Before taking tamoxifen, tell your doctor if you
- have a history of deep vein thrombosis (blood clot in the leg);
- have a history of pulmonary thrombosis (blood clot in the lung); or
- take the blood thinner warfarin (Coumadin).

You may not be able to take tamoxifen, or you may require a dosage adjustment or special monitoring during treatment.

Tamoxifen is in the FDA pregnancy category D. This means that tamoxifen is known to be harmful to an unborn baby. Do not take tamoxifen without first talking to your doctor if you are pregnant or could become pregnant during or for two months following treatment. Effective nonhormonal contraception (birth control) should be used during and for two months following treatment with tamoxifen.

It is not known whether tamoxifen passes into breast milk. Do not take tamoxifen without first talking to your doctor if you are breast-feeding a baby.

How should take tamoxifen

Take tamoxifen exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.

Take each dose with a full glass (8 ounces) of water.

Tamoxifen can be taken with or without food.

It is important to take tamoxifen regularly to get the most benefit.

Your doctor may want you to have breast exams (or to perform self breast exams), mammograms, blood tests, or other medical evaluations during treatment with tamoxifen to monitor progress and side effects.

Store tamoxifen at room temperature away from moisture and heat.

If you miss a dose:

Take the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and take only the next regularly scheduled dose. Do not take a double dose of this medication unless your doctor directs otherwise.

What happens if you overdose:

An overdose of tamoxifen is unlikely to threaten life. Call an emergency room or a poison control center for advice if you suspect an overdose.

Symptoms of a tamoxifen overdose are unknown, but nausea, vomiting, seizures, tremor, or dizziness may be expected.

Avoid while taking tamoxifen

There are no restrictions on food, beverages, or activity during treatment with tamoxifen unless otherwise directed by your doctor.

Possible side effects of tamoxifen

Stop taking tamoxifen and seek emergency medical attention or contact your doctor immediately if you experience any of the following serious side effects:
- an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);
- possible symptoms of a stroke such as unusual weakness, drowsiness, confusion, or difficulty walking or talking;
- possible symptoms of a blood clot in the lung such as chest pain, shortness of breath, or coughing up blood;
- possible symptoms of a blood clot in the brain or leg such as blurred vision, changes in vision, numbness, or pain or swelling in a leg;
- new breast lumps;
- bone pain;
- menstrual changes, abnormal vaginal bleeding, vaginal discharge, or pelvic pain or pressure;
- pain or tenderness in the upper abdomen;
- yellowing of the skin or eyes; or
- excessive nausea, vomiting, or thirst.

Other, less serious side effects may be more likely to occur. Continue to take tamoxifen and talk to your doctor if you experience
- dizziness or headache;
- mild nausea, vomiting, or decreased appetite;
- vaginal itching;
- hot flashes; or
- changes in weight.

Treatment with tamoxifen may increase the risk of certain uterine cancers, stroke, and pulmonary embolism (blood clot in the lung), which may be fatal. You should discuss with your doctor the risks and benefits associated with the use of tamoxifen.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

What other drugs will affect tamoxifen

Before taking tamoxifen, tell your doctor if you are taking
- an estrogen such as Premarin, Ogen, Estratest, Estraderm, Vivelle, Climara, and others;
- a birth control pill that contains estrogen;
- warfarin (Coumadin) or another blood thinner; or
- bromocriptine (Parlodel).

You may not be able to take tamoxifen or you may require special monitoring or a dosage adjustment if you are taking any of the medicines listed above.

Drugs other than those listed here may also interact with tamoxifen. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines, including herbal products.

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