Selective estrogen receptor modulators (SERMs) are medications that can block or activate estrogen in different tissues. SERMs can target a variety of estrogen receptors in the body, such as in the breast, uterus, and bones. SERMs are often used to treat estrogen-related diseases like osteoporosis and breast cancer.

This article explains the types of SERM drugs, their benefits, potential side effects, and safety information.

Types of SERM Drugs

The three SERM drugs most commonly used are tamoxifen, raloxifene and toremifene.

Nolvadex and Soltamox (Tamoxifen)

Tamoxifen, under the brand names Nolvadex and Soltamox, is the oldest and most-prescribed SERM. Tamoxifen is approved by the U.S. Food and Drug Administration (FDA) for the following uses:

• To treat women and men diagnosed with estrogen receptor (ER)-positive advanced stage or metastatic breast cancer
• To reduce the risk of recurrence in those diagnosed with ER-positive early-stage breast cancer after surgery, chemotherapy, and/or radiation
• To prevent breast cancer in those who have an increased genetic risk of developing the disease
  

Evista (Raloxifene)

Evista (raloxifene) is a SERM approved by the FDA to:

• Treat and prevent osteoporosis in postmenopausal women
• Reduce the risk of ER-positive breast cancer in postmenopausal women who haven't been diagnosed but are at increased risk for the disease
• Reduce the risk of ER-positive breast cancer in postmenopausal women being treated for osteoporosis but who haven't been diagnosed with breast cancer
  

Fareston (Toremifene)

Fareston (toremifene) is approved by the FDA to treat postmenopausal women diagnosed with advanced (metastatic) ER-positive breast cancer.

You should not take Fareston if you are breastfeeding, pregnant, trying to get pregnant, or if there's any chance that you could be pregnant. 

Benefits of SERMs

SERMs can help with many conditions. But, because each SERM works differently, your healthcare provider will guide you to the one that will work best for your circumstances.

For Osteoporosis

Fareston is commonly used to help treat osteoporosis because it mimics the benefits of estrogen on bone density. Studies suggest that it can increase bone density by 2% to 3% in the lower spine and hips. Fareston may also reduce vertebral fractures by up to 50% and lead to a 22% decrease in other major fractures.

For Breast Cancer

SERMs, particularly Nolvadex and Soltamox, are often used to help treat ER-positive breast cancer.

Estrogen in the body binds to proteins on the surface of these cells (estrogen receptors) to signal the cell to divide and grow. Tamoxifen binds to this receptor, essentially starving the cancer cells.

When used after primary treatment (e.g., surgery), it may reduce your risk of breast cancer recurrence by half if your tumor was ER-positive. The drug continues to have this benefit even after you stop taking it.

Tamoxifen can also reduce your risk of developing another cancer in the same breast or new cancer in your other breast by up to 50%.

Taking Nolvadex and Soltamox or Evista can even reduce some women’s risk of developing breast cancer in the first place. The U.S. Preventive Services Task Force (USPSTF) recommends these medications for women who are at a high risk of developing breast cancer and at low risk for medication side effects.

For Other Conditions

Serophene (clomiphene) is another SERM. It is commonly used in female fertility prescription medications, such as Clomid. In women, Serophene acts on the pituitary gland to stimulate the release of specific hormones responsible for ovulation.

You may also be prescribed a SERM combination, such as Duavee (bazedoxifene and a mixture of estrogen hormones known as conjugated estrogen). Duavee may help to reduce uncomfortable menopause symptoms, such as vaginal dryness and hot flashes.

SERMs vs Aromatase Inhibitors

SERMs work by blocking the effects of estrogen on breast tissue. Aromatase inhibitors (AIs) work by blocking an enzyme (aromatase) that is responsible for producing estrogen within the body in postmenopausal women. When treating early-stage, ER-positive breast cancer, aromatase inhibitors have more benefits and fewer serious side effects than tamoxifen.

Side Effects of SERMs

SERMs, like any medication, come with side effects. Some of these side effects can be mildly unpleasant, and some may be potentially dangerous.

Evista (Raloxifene) Side Effects

The most common side effects of Evista are:

• Hot flashes
• Leg cramps
• Swelling
• Flu-like symptoms
• Sleeping problems
• Joint/bone pain
• Sweating
• Dry skin

Evista can cause some serious side effects, including blood clots and stroke. If you're taking Evista, call your healthcare provider immediately if you have any of these symptoms: 

• Leg pain or warmth in the calves
• Swelling of the legs, hands, or feet 
• Chest pain
• Shortness of breath
• Vision problems
• Weakness
• Difficulty speaking or understanding
• Sudden severe headache

Nolvadex and Soltamox Side Effects

Many of the common side effects of Nolvadex and Soltamox are essentially the same as those that occur during menopause when there's a reduced amount of estrogen in the body.

Common side effects of Nolvadex and Soltamox include:

• Hot flashes
• Night sweats
• Vaginal dryness
• Vaginal discharge
• Reduced libido
  

There are also a number of medications that Nolvadex and Soltamox interact with, meaning you may have to make changes to your regular medication in order to take this SERM.

Are SERMs Safe?

Tell your healthcare providers about any blood clots or clotting disorders you have. SERMs may increase your risk of developing new ones and make existing clots worse. You should also tell them about any kidney or liver conditions. These can cause higher concentrations of SERMs in your blood.

The actions of Nolvadex and Soltamox on endometrial tissue can raise the risk of uterine cancer. The risk is highest for postmenopausal women, but it's still rare. Premenopausal women treated with tamoxifen have no known increased risk of uterine cancer and require no additional monitoring beyond routine gynecologic care.

SERMs are also not recommended for women who are pregnant or breastfeeding.

Summary

SERMs are medications that can both block and mimic the effects of estrogen in different parts of your body. This makes them valuable for helping to treat conditions like osteoporosis and estrogen receptor-positive breast cancer. While they can cause some side effects, the benefits often outweigh the downsides.

A Word From Verywell

SERMS have been shown to have real health benefits for premenopausal and menopausal women. Ask your healthcare provider about SERMs and discuss the risks and benefits before deciding if this hormone therapy is right for you.