Specific Precautions and Warnings for Fareston
Some warnings and precautions to be aware of prior to taking this drug include the following:
- Fareston may cause a potentially dangerous heart problem known as QT prolongation, which can lead to a life-threatening arrhythmia (abnormal heartbeat). Because low blood potassium or magnesium levels increase your risk for QT prolongation, your healthcare provider will check your levels with a simple blood test before you start treatment and periodically thereafter.
If you are at risk for QT prolongation, your healthcare provider may want to check the electrical activity of your heart with an electrocardiogram (ECG), before you start Fareston.
- Some women, particularly those whose cancer has spread to the bone, may experience a sudden increase in symptoms, such as an increase in the size of their tumors, muscle and bone pain, and skin rash, shortly after starting Fareston. Blood calcium levels may also increase. This reaction (known as tumor flare) is usually only temporary and does not mean the medicine is not working. If your blood calcium levels are extremely high, however, your healthcare provider may recommend you stop taking this drug.
- Fareston may cause the lining of the uterus (the endometrium) to grow and thicken, which could increase your chance of getting endometrial cancer. Some women who were treated with this drug developed endometrial cancer. You should report any unexplained vaginal bleeding to your healthcare provider, as it may be a sign of this disease.
- Because of the risks associated with its use, this medication may not be the best choice for women who have had a blood clot. It also generally should not be used for a long period of time in women who have had endometrial hyperplasia (abnormal growth and thickening of the endometrium).
- Your healthcare provider will order certain blood tests periodically during treatment to make sure you are not developing potentially dangerous Fareston side effects. This may include blood tests to check your calcium levels, liver function, platelets, and white blood cells. Make sure to keep all your healthcare and laboratory appointments during treatment.
- Fareston is a pregnancy Category D medication, which means it may harm an unborn child if taken during pregnancy (see Fareston and Pregnancy).
- It is unknown if Fareston passes through breast milk. Therefore, if you are breastfeeding or plan to start, discuss this with your healthcare provider prior to taking the drug (see Fareston and Breastfeeding).