May 23 2022

Classification of the active ingredient anastrozole


Risk level in pregnancy: This medicine is classified as Category X.

There are no systematic studies in humans on the use of anastrozole during pregnancy. Animal experimentation has revealed intrauterine growth retardation and fetal loss.

In reproductive toxicity studies in pregnant rodents treated with therapeutic doses, anastrozole crossed the placenta and there was a decrease in the numbers of live fetuses, and fetal toxicity signs, as decreased fetal weight and ossification defects.

The active ingredient Anastrozole may cause fetal harm when administered to a pregnant woman and offers no clinical benefit to premenopausal women with breast cancer. Therefore, this drug is contraindicated in women who are or may become pregnant. However, in special and exceptional circumstances, any benefits from the use of this drug may outweigh the potential risk. For example, the risk of anastrozole may be acceptable if it is necessary in a life threatening situation or a serious disease for which can not be used or are not effective other medicines.

If this drug is used during pregnancy or the patient becomes pregnant while taking this drug, should be apprised of the potential hazard to the fetus and possible loss of pregnancy.

Update 06.06.2010

Meaning of category X

Studies in animals or humans have demonstrated fetal abnormalities and/or there is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience, and the risks involved in use of the drug in pregnant women clearly outweigh potential benefits.