I'm Pregnant -- Can I Take Propylthiouracil?
) is a prescription antithyroid medication used to treat hyperthyroidism
(an overactive thyroid
). This medication may pose some risk to the developing fetus if taken during pregnancy, but is usually thought to be safer for the first trimester
of pregnancy than methimazole
, which is often used as an alternative to propylthiouracil.
What Is Pregnancy Category D?
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. Pregnancy Category D is 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.
In other words, a pregnancy Category D medicine may still be given to a pregnant woman if the healthcare provider believes that the benefits to the woman outweigh the possible risks to the unborn child.
Propylthiouracil crosses the placenta. However, it seems to have a lower risk for birth defects, compared to methimazole, another antithyroid medication. Although methimazole is preferred over propylthiouracil in almost all situations, since propylthiouracil has a higher risk of liver failure, women are generally recommended to avoid methimazole during the first trimester of pregnancy.
No matter what treatment is chosen, your healthcare provider should monitor your thyroid levels closely during pregnancy, because pregnancy can affect thyroid function. Untreated hyperthyroidism is associated with problems such as certain birth defects, so it is essential that pregnant women be adequately treated for this condition.