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Is it safe for pregnant women to take Samsca (tolvaptan)? Animal studies have shown that this drug may delay fetal bone formation, cause miscarriages, and increase the risk for birth defects. However, research in pregnant women is lacking, so it is unknown whether this drug would cause similar problems in humans.
Samsca® (tolvaptan) is a prescription medicine used to treat low blood sodium (salt) levels that can result from certain medical conditions. Based on the results of animal studies, this medication may not be safe for use during pregnancy, although the full risks are currently unknown.
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. Samsca is classified as a pregnancy Category C medicine.
Pregnancy Category C is given to medicines that have not been studied in pregnant humans but do appear to cause harm to the fetus in animal studies. Also, medicines that have not been studied in any pregnant women or animals are automatically given a pregnancy Category C rating.
Samsca has not been adequately studied in pregnant women. However, the drug caused a variety of problems when given to pregnant animals. In these studies, Samsca delayed fetal bone formation and reduced the weight of the rat fetuses when given in high doses to pregnant rats. When given to pregnant rabbits, it increased the risk for miscarriage and birth defects, including cleft palate (a birth defect in which the roof of the mouth does not form properly) and abnormalities of the limbs (arms and legs), eyes, and bones.
However, it is important to note that animals do not always respond to medicines in the same way that humans do. Therefore, a pregnancy Category C medicine may be given to a pregnant woman if her healthcare provider believes that the benefits to the woman outweigh any possible risks to her unborn child.