Fareston and Pregnancy
When Fareston (toremifene) was given to pregnant animals, it appeared to cause miscarriages, birth defects, and other complications. Due to these potential risks, this drug is considered a pregnancy Category D medicine, meaning it may cause fetal harm. In general, this medicine is not used in pregnant women because it is designed for use in postmenopausal women.
Fareston® (toremifene citrate) is a prescription medication used to treat advanced breast cancer in postmenopausal women. It belongs to a group of medicines known as selective estrogen receptor modulators. Based on animal studies, Fareston may harm an unborn child if taken during pregnancy.
The U.S. Food and Drug Administration (FDA) uses a category system to classify the possible risks to a fetus when a specific medicine is taken during pregnancy. Fareston is classified as a pregnancy Category D medication.
Pregnancy Category D is a classification given to medicines that have been shown to present a risk to the fetus in studies of pregnant women but may still offer benefits that outweigh the risks the drug presents. A pregnancy Category D medicine may still be given to a pregnant woman if her healthcare provider believes that the benefits to the woman outweigh the possible risks to her unborn child.
Fareston has not been studied in pregnant women. The drug caused a variety of problems in animal studies. When given to pregnant rats, it increased the risk for miscarriage, reduced fetal body weight, and caused birth defects, including problems with the bones, limbs (arms and legs), and kidneys. These problems occurred even at doses that were lower than the normally recommended human dose.
Similar problems were observed when Fareston was given to pregnant rabbits. However, the drug also called brain and skull defects in the rabbit fetuses.
In addition, Fareston prevented the normal development of the uterus in female rodents exposed to the drug as fetuses. Similar problems were observed when another selective estrogen receptor modulator known as tamoxifen (Nolvadex®, Soltamox®) was given to pregnant rodents.
It is important to keep in mind that Fareston is only approved for use in postmenopausal women. However, any premenopausal woman who takes the drug should use an effective nonhormonal birth control throughout treatment to prevent pregnancy.