- Treatment of metastatic breast cancer (cancer that has spread beyond the breasts) in men and women
- Treatment of node-positive breast cancer (breast cancer that involves the lymph nodes) in postmenopausal women who have undergone breast cancer surgery or radiation
- Treatment of ductal carcinoma in situ (DCIS), which is early cancer of the ducts of the breasts that has not yet spread to the rest of the breast, in women who have undergone breast cancer surgery or radiation to reduce the risk of invasive breast cancer
- Breast cancer prevention in women who are at high risk for the disease.
Brand-name tamoxifen was made by AstraZeneca Pharmaceuticals, but is no longer being made. However, generic tamoxifen is available and is made by several different manufacturers.
Tamoxifen is part of a group of medications called selective estrogen receptor modulators (SERMs). SERMs have both estrogenic (estrogen-like) effects and anti-estrogenic effects. Tamoxifen has anti-estrogenic effects on the breasts, while it has estrogen-like effects on bones, helping to strengthen them.
Many
breast cancers are sensitive to the estrogen hormone, meaning that the tumor grows with the help of estrogen. When a tumor is sensitive to estrogen, it has receptors on the outer surface of its cells. Estrogen fits into these receptors like a key opening a lock. When this connection is made, the cancer grows. Breast cancers that have estrogen (and/or progesterone) receptors are known as hormone receptor-positive tumors.
Tamoxifen binds to estrogen receptors in the breast, preventing estrogen from binding. By decreasing these effects of estrogen, the drug can help decrease the growth of these breast cancers. This type of
breast cancer treatment is known as hormonal therapy
(see Breast Cancer Hormone Treatment).
Several studies have looked at the effects of tamoxifen in women with breast cancer, especially when used as an adjuvant therapy of early breast cancer.
Adjuvant therapy for breast cancer is treatment that follows
breast cancer surgery (with or without radiation). It is given to help prevent the cancer from returning. These studies included women with cancer that was either hormone receptor-positive or hormone receptor-unknown. More women survived after 5 and 10 years on tamoxifen compared to those not taking the drug.
Other studies have shown that tamoxifen can help prevent breast cancer in women with ductal carcinoma in situ (DCIS) who have had surgery and radiation. About 17 in every 1,000 women not taking the drug developed invasive breast cancer per year, compared to only about 10 in every 1,000 women per year taking tamoxifen.
Tamoxifen can also prevent breast cancer in women who are at high risk for the disease. In studies, the drug reduced the risk of developing breast cancer by as much as 44 percent.
When and How to Take Tamoxifen
General considerations for when and how to take it include the following:
- The medication comes in tablet form and is taken by mouth once or twice a day.
- You can take it with or without food. If tamoxifen bothers your stomach, try taking it with food.
- The medication should be taken at the same time(s) each day to maintain an even level in your blood.
- For the medication to work properly, it must be taken as prescribed. It will not work if you stop taking it.
The dose of tamoxifen that your healthcare provider recommends will vary, depending on a number of factors, including:
- The severity of your breast cancer (see Breast Cancer Stages)
- Whether you are using tamoxifen to treat or prevent breast cancer
- Other medications you may be taking
- Other medical conditions you may have.
As is always the case, do not adjust your dose unless your healthcare provider specifically instructs you to do so.
As with any medicine, side effects are possible with tamoxifen. However, not everyone who takes the drug will experience side effects. In fact, most people tolerate it quite well. If side effects do occur, in most cases, they are minor and either require no treatment or can easily be treated by you or your healthcare provider. Serious side effects are less common.
Common side effects of tamoxifen include, but are not limited to:
- Hot flashes
- Vaginal discharge
- Fluid retention
- Nausea
- Irregular menstrual periods.
(Click Tamoxifen Side Effects to learn more, including potentially serious side effects that you should report immediately to your healthcare provider.)
The following eMedTV articles describe specific side effects of tamoxifen:
What Should I Tell My Healthcare Provider?
You should talk with your healthcare provider prior to taking this drug if you have:
- Unexplained vaginal bleeding
- A history of blood clot or stroke
- Any allergies, including allergies to food, dyes, or preservatives.
Also, let your healthcare provider know if you are:
Make sure to tell your healthcare provider about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements.
What If I Take an Overdose of Tamoxifen?
People who take too much tamoxifen may have symptoms that include:
- Shakiness (tremor)
- Overactive reflexes
- Unsteady walking
- Dizziness
- Irregular heart rhythm (arrhythmia)
- Seizures.
It should be stored at room temperature, away from moisture and heat. Store the tablets in an airtight container.
Keep tamoxifen and all medications out of the reach of children.
What Should I Do If I Miss a Dose?
If you do not take your tamoxifen as scheduled, take your missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and continue with your regular schedule. Do not take a double dose.
Generic tamoxifen tablets are available in the following strengths:
- Tamoxifen 10 mg
- Tamoxifen 20 mg.
A liquid form of tamoxifen is also available -- Soltamox™ oral solution (10 mg per 5 mL, equivalent to 10 mg per teaspoonful).
Is There a Generic Version of Tamoxifen?
Since brand-name tamoxifen is no longer available, it is fortunate that many different manufacturers have chosen to make generic tamoxifen.
