Which of the following drugs is classified under Category X pregnancy risk?

Warfarin is classified under Category X for pregnancy risk due to its known teratogenic effects and the serious risks it poses to a developing fetus. During pregnancy, Warfarin can cross the placenta and has been associated with a range of complications, including congenital malformations, fetal hemorrhage, and stillbirth. These risks lead to the categorization of Warfarin as Category X, indicating that it should not be used during pregnancy because the potential risks clearly outweigh any possible benefits.

Other medications listed have different classifications or implications for use during pregnancy. For example, Meropenem is generally considered safer and is not classified as Category X. Benadryl, while used with caution in pregnancy, is not categorized in the same way and is often used for allergy treatment. Ibuprofen, though advised against during the third trimester, is also not classified as Category X across throughout pregnancy. Thus, the significant risks associated with Warfarin use in pregnancy justify its classification as Category X.