Use this medicine only as directed by your doctor. Do not use more or less of it, and do not use it more often than your doctor ordered. The exact amount of medicine you need has been carefully worked out. Taking too much may increase the chance of side effects, while taking too little may not improve your condition.

Tamoxifen sometimes causes mild nausea and vomiting. However, it may have to be taken for several weeks or months to be effective. Even if you begin to feel ill, do not stop using this medicine without first checking with your doctor. Ask your health care professional for ways to lessen these effects.

Swallow the tablets whole with a drink of water. You can take the tablets with or without food.

If you vomit shortly after taking a dose of tamoxifen, check with your doctor. You will be told whether to take the dose again or to wait until the next scheduled dose.

Dosing

The dose of tamoxifen will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of tamoxifen. If your dose is different, do not change it unless your doctor tells you to do so.

• For oral dosage form (tablets)
  • For breast cancer in women or men:
    • Adults 20 to 40 milligrams (mg) daily.
  • For reducing the risk of developing breast cancer in high-risk women:
    • Adults 20 milligrams (mg) a day, for five years
  • For reducing the risk of developing invasive breast cancer in women with ductal carcinoma in situ:
    • Adults 20 milligrams (mg) a day, for five years

Missed dose

If you miss a dose of this medicine, do not take the missed dose at all and do not double the next one. Instead, go back to your regular dosing schedule and check with your doctor.

Storage

To store this medicine:

• Keep out of the reach of children.
• Store away from heat and direct light.
• Do not store in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down.
• Do not keep outdated medicine or medicine no longer needed. Be sure that any discarded medicine is out of the reach of children.

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For tamoxifen, the following should be considered:

Allergies Tell your doctor if you have ever had any unusual or allergic reaction to tamoxifen.

Pregnancy Tell your doctor if you are pregnant or if you intend to become pregnant. Tamoxifen should not be used to reduce the risk of breast cancer if you are pregnant of if you intend to become pregnant. Tamoxifen use in women has been shown to cause miscarriages, birth defects, death of the fetus, and vaginal bleeding. Studies in rats and rabbits have shown that tamoxifen causes miscarriages, death of the fetus, and slowed learning. Studies in animals also have shown that tamoxifen may cause some of the same problems as those caused by an estrogen called diethylstilbestrol (DES). DES causes genital tract problems and, rarely, an increased risk of cancer of the cervix or vagina in daughters of women who took it during their pregnancy. It is not known whether tamoxifen causes these same problems.

Be sure that you have discussed this with your doctor before taking this medicine. It is best to use some kind of birth control while you are taking tamoxifen and for about 2 months after you stop taking it. However, do not use oral contraceptives (?the Pill?) since they may interfere with this medicine. Tell your doctor right away if you think you have become pregnant while taking tamoxifen.

Breast-feeding Because this medicine may cause serious side effects, breast-feeding is generally not recommended while you are taking it.

Older adults Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults. Although there is no specific information comparing use of tamoxifen in the elderly with use in other age groups, this medicine is not expected to cause different side effects or problems in older people than it does in younger adults.

Other medicines Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. Tell your health care professional if you are taking any other prescription or nonprescription (over-the-counter [OTC]) medicine. If you are taking tamoxifen to reduce the risk of breast cancer, it is especially important that your health care professional know if you are taking the following:

• Anticoagulant, coumarin-type (blood thinners) Blood thinners (e.g., warfarin [Coumadin]) should not be used with tamoxifen when used to reduce the risk of developing breast cancer in women who have a high risk of developing breast cancer. If you need to take blood thinners, your blood clotting times should be monitored by your doctor.

• Cytotoxic medicines These are medicines that damage cells. If you take these medicines with tamoxifen, you may have an increased risk of blood clots.

For all patients
• Blood problems or
• Cataracts or other eye problems Tamoxifen may also cause these problems

• High cholesterol levels in the blood Tamoxifen can increase cholesterol levels

When used for reducing the risk for developing breast cancer in high-risk women or in women with Ductal Carcinoma in Situ (DCIS)
• Blood clots (or history of) or
• Pulmonary embolism (or history of) or
• Stroke or
• Uterine (womb) cancer May increase risk of serious side effects from tamoxifen.