Medically reviewed by Drugs.com. Last updated on Oct 15, 2023.
Toremifene prolongs the QTc interval in a dose- and concentration-related manner and may cause a type of ventricular tachycardia called Torsade de pointes. This could result in syncope, seizures, and/or death. Toremifene should not be prescribed to patients with congenital/acquired QT prolongation, uncorrected hypokalemia, or uncorrected hypomagnesemia. Drugs known to prolong the QT interval and strong CYP3A4 inhibitors should be avoided .
Uses for Fareston
Toremifene is used to treat metastatic breast cancer (cancer that has spread) that is hormone-receptor positive in women who have already stopped menstruating (postmenopausal).
Many of the breast cancer tumors will grow when estrogen is available in the body. This medicine blocks the effects of the estrogen hormone. As a result, the amount of estrogen that the tumor is exposed to is reduced, which will limit the growth of the tumor.
This medicine is available only with your doctor's prescription.
Before using Fareston
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 this medicine, the following should be considered:
Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.
Toremifene is not indicated for use in the pediatric population. Safety and efficacy have not been established.
Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of toremifene in the elderly. However, elderly patients are more likely to have age-related liver problems, which may require caution and an adjustment in the dose for patients receiving toremifene.
There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.
Interactions with 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. When you are taking this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
- Aripiprazole Lauroxil
- Arsenic Trioxide
- Inotuzumab Ozogamicin
- Sodium Phosphate
Interactions with Food/Tobacco/Alcohol
Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.
Using this medicine with any of the following is usually not recommended, but may be unavoidable in some cases. If used together, your doctor may change the dose or how often you use this medicine, or give you special instructions about the use of food, alcohol, or tobacco.
- Grapefruit Juice
Other Medical Problems
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:
- Blood clots, or history of—Use is usually not recommended in patients with this condition.
- Bone problems (eg, bone cancer) or
- Congestive heart failure or
- Heart rhythm problems (eg, QT prolongation) or
- Leukopenia (low white blood cells in the blood) or
- Thrombocytopenia (low platelets in the blood)—Use with caution. May make these conditions worse.
- Heart rhythm problems (eg, congenital or acquired long QT syndrome) or
- Hypokalemia (low potassium in the blood), uncorrected or
- Hypomagnesemia (low magnesium in the blood), uncorrected—Should not be used in patients with these conditions.
- Liver disease (eg, cirrhosis, fibrosis)—Use with caution. The effects may be increased because of slower removal of the medicine from the body.
- Unusual growth of the lining of the uterus (womb)—Long-term use of toremifene is usually not recommended.
Proper use of Fareston
Medicines used to treat cancer are very strong and can have many side effects. Before receiving this medicine, make sure you understand all the risks and benefits. It is important for you to work closely with your doctor during your treatment.
Use this medicine only as directed by your doctor. Do not use more of it, do not use it more often, and do not use it for a longer time than your doctor ordered.
Do not eat grapefruit or drink grapefruit juice while you are using this medicine.
The dose of this medicine 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 this medicine. If your dose is different, do not change it unless your doctor tells you to do so.
The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.
- For oral dosage form (tablets):
- For breast cancer:
- Adults—60 milligrams (mg) once a day.
- Children—Use is not recommended.
- For breast cancer:
If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.
Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.
Keep out of the reach of children.
Do not keep outdated medicine or medicine no longer needed.
Ask your healthcare professional how you should dispose of any medicine you do not use.
Precautions while using Fareston
It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly. Blood tests may be needed to check for unwanted effects. It is important for women to have regular gynecologic check-ups while taking this medicine.
It is unlikely that a postmenopausal woman may become pregnant. But, using this medicine while you are pregnant could harm your unborn baby. If you are a woman who can bear children, your doctor may give you a pregnancy test before you start using this medicine to make sure you are not pregnant. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using this medicine, tell your doctor right away.
Contact your doctor right away if you have any changes to your heart rhythm. You might feel dizzy or faint, or you might have a fast, pounding, or uneven heartbeat. Make sure your doctor knows if you had a heart rhythm problem, such as QT prolongation.
Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin. These could be symptoms of a serious liver problem.
Hypercalcemia (high calcium in the blood) and tumor flare (increased size of a tumor) are more likely to occur in patients with bone problems who are taking this medicine. Check with your doctor right away if you have stomach pain, confusion, constipation, depression, dry mouth, increased urination, loss of appetite, metallic taste, muscle weakness, pain and swelling in the bones and muscles surrounding a tumor, thirst, unusual tiredness, or weight loss.
This medicine may increase your risk of having uterus problems, including endometrial cancer. Talk with your doctor if you have concerns about this.
Toremifene can temporarily lower the number of white blood cells in your blood, increasing the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:
- If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
- Check with your doctor immediately if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine or stools, or pinpoint red spots on your skin.
- Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
- Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
- Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
- Avoid contact sports or other situations where bruising or injury could occur.
This medicine may cause you to have bleeding from the vagina, especially when you first start using it. If the bleeding continues or is bothersome, check with your doctor right away.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal (eg, St. John's wort) or vitamin supplements.
Side Effects of Fareston
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
- arm, back, or jaw pain
- blurred vision
- change in how much and how often you urinate
- change in vaginal discharge
- changes in skin color
- changes in vision
- changes in weight
- chest pain, discomfort, tightness, or heaviness
- dilated neck veins
- dizziness, lightheadedness
- dry mouth
- fast, slow, or irregular heartbeat
- inability to speak, incoherent speech
- irregular breathing
- loss of appetite
- metallic taste in the tongue
- muscle weakness
- pain or discomfort in the arms, jaw, back, or neck
- pain or feeling of pressure in the pelvis
- pain, tenderness, or swelling of the foot or leg
- severe or sudden headache
- stomach pain
- swelling of the face, fingers, feet, or lower legs
- temporary blindness
- tenderness, pain, swelling, warmth, skin discoloration, prominent superficial veins over the affected area
- troubled breathing
- unusual tiredness or weakness
- vaginal bleeding
- weakness in the arm and or leg on one side of the body, sudden and severe
Incidence not known
- Black, tarry stools
- bleeding gums
- blood in the urine or stools
- clay-colored stools
- dark urine
- painful or difficult urination
- pinpoint red spots on the skin
- sore throat
- sores, ulcers, or white spots on the lips or in the mouth
- swollen glands
- unpleasant breath odor
- unusual bleeding or bruising
- vomiting of blood
- yellow eyes or skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
- decreased vision
- dry eyes
- feeling of warmth
- redness of the face, neck, arms, and occasionally, the upper chest
- sudden sweating
- Bone pain
- changes in vision
- double vision
- eye pain
Incidence not known
- Blistering, crusting, irritation, itching, or reddening of the skin
- cracked, dry, or scaly skin
- difficulty having a bowel movement
- feeling of constant movement of self or surroundings
- feeling unusually cold
- hair loss
- lack or loss of strength
- partial or slight paralysis
- sensation of spinning
- shakiness in the legs, arms, hands, or feet
- thinning of the hair
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
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