Toremifene (Fareston®)

Author: OncoLink Team
Last Reviewed: August 26, 2019

Pronounced: tore-EM-i-feen

Classification: Antiestrogen

About: Toremifene (Fareston®)

Toremifene is in a class of medications called selective estrogen receptor modulators or SERMs. Most breast cancers need supplies of estrogen (a female hormone produced by the body) to grow. Toremifene decreases the risk of developing invasive breast cancer by blocking the effects of estrogen on breast tissue. This may stop the development of tumors that need estrogen to grow.

How to Take Toremifene

Toremifene comes as a tablet to be taken orally (by mouth) around the same time each day, with or without food. This medication can affect certain blood levels so you will frequently have labs drawn to monitor these levels. 

It is important to make sure you are taking the correct amount of medication every time. Before every dose, check that what you are taking matches what you have been prescribed.

The blood levels of this medication can be affected by certain foods and medications, so they should be avoided. These include: grapefruit, grapefruit juice, verapamil, ketoconazole, rifampin, phenytoin, St. John’s wort, and modafanil, among others. Be sure to tell your healthcare provider about all medications and supplements you take.

Women should use a non hormonal method of birth control (condoms, sponge, diaphragm) while taking this medication.

Storage and Handling

Store this medication at room temperature in the original container. If you prefer to use a pillbox, discuss this with your oncology pharmacist. Ask your oncology team where to return any unused medication for disposal. Do not flush down the toilet or throw in the trash. 

Where do I get this medication?

Toremifene is is available through retail or mail order pharmacy. Your oncology team will work with your prescription drug plan to identify an in-network, retail or mail order pharmacy for medication distribution. 

Insurance Information

This medication may be covered under your prescription drug plan. Patient assistance may be available to qualifying individuals without prescription drug coverage. Co-pay cards, which reduce the patient co-pay responsibility for eligible commercially (non-government sponsored) insured patients, are also available. Your care team can help you find these resources, if they are available.

Possible Side Effects of Toremifene

There are a number of things you can do to manage the side effects of toremifene. Talk to your care team about these recommendations. They can help you decide what will work best for you. These are some of the most common or important side effects: 

Heart Problems

This medication can cause slow or abnormal heartbeats or an abnormal heart rhythm called QT prolongation. Notify your healthcare provider right away if you feel abnormal heartbeats or if you feel dizzy or faint.

Hot Flashes and Sweating

There are a few things you can do to help with hot flashes and sweating. Several medications have been shown to help with hot flash symptoms, including clonidine (a blood pressure medication), low doses of certain antidepressants (such as venlafaxine and fluoxetine), and gabapentin.  Talk to your healthcare team about these prescription products to determine if they are right for you.

Non-medical recommendations include:

  • Keep well-hydrated with eight glasses of water daily.
  • Drink ice water or apply an ice pack at the onset of a hot flash.
  • Wear cotton or lightweight, breathable fabrics and dress in layers so you can adjust as needed.
  • Exercise on a regular basis.
  • Try practicing meditation or relaxation exercises to manage stress, which can be a trigger.
  • Avoid triggers such as warm rooms, spicy foods, caffeinated beverages, and alcohol. 

Less common but important side effects can include:

  • Secondary Cancers: A secondary cancer is one that develops as a result of cancer treatment for another cancer. This is quite rare, but you should be aware of the risk. In most cases, a secondary cancer related to chemotherapy is a blood cancer (leukemia, lymphoma). This can occur years after treatment. This is most often associated with repeated treatments or high doses. Your provider will monitor your labs closely. Consider having a complete blood count with differential checked annually by your healthcare provider if you received high risk therapies.
  • Bone Metastases: Patients with cancer that has spread to the bone may experience pain or discomfort at the tumor site after starting toremifene, but this should decrease over time and should be managed with pain medication.In addition, patients with bone metastases may develop hypercalcemia (high levels of calcium in the blood) and may require hospitalization to correct this. Symptoms of hypercalcemia include increased thirst and urination, nausea, constipation, muscle weakness, confusion or changes in mental status. Report any symptoms to your care provider.
  • Blood Clots: This medication increases the risk of developing a blood clot, which most frequently occurs in the calves, and can travel from there to the lungs. Women at higher risk for developing blood clots include those with a family history of blood clots, heavy smokers, those who have an inactive lifestyle, older women, and those with other predisposing medical problems. Women with any one of these risk factors may want to consider another therapy that does not have this side effect. Being immobile increased the risk of a blood clot. You should stop taking this medication 3 days prior to and during any prolonged immobilization (hospitalization or bed rest). When traveling, be sure to get up and move around frequently to reduce the risk of a clot. Signs of a blood clot in the leg may include any of the following: leg pain, warmth, swelling of one leg more than the other. Signs of a blood clot in the lung could include: fever, shortness of breath that comes on very quickly, racing heart, chest pain (that tends to be worse when you take a deep breath). If you have any of these signs or symptoms of blood clots, you may have a clot and should call your provider right away for treatment.
  • Other side effects: Headache, swelling of the hands and/or feet, dizziness, weight gain, vaginal discharge and insomnia. Mood changes or depression can occur. Please talk to your healthcare provider if you feel that you are troubled by these side effects.

Sexual & Reproductive Concerns

Women may experience menopausal effects including hot flashes and vaginal dryness. In addition, the desire for sex may decrease during treatment.

Exposure of an unborn child to this medication could cause birth defects, so you should not become pregnant while on this medication. Effective birth control is necessary during treatment even if your menstrual cycle stops. You should consult with your healthcare team before breastfeeding while receiving this medication.

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