Methimazole Pregnancy and Breast Feeding Warnings
Methimazole is also known as: Northyx, Tapazole
Overview
Methimazole has been shown to cause harm to the fetus. If you think you may be pregnant, contact your doctor. You will need to discuss the benefits and risks of using Methimazole while you are pregnant. Methimazole is found in breast milk. Do not breast-feed while taking Methimazole .
Methimazole Pregnancy Warnings
Methimazole has been assigned to pregnancy category D by the FDA. Methimazole readily crosses the placental membranes and can induce goiter and cretinism in the developing fetus. In addition, rare instances of congenital defects: aplasia cutitis, as manifested by scalp defects; esophageal atresia with tracheoesophageal fistula; and choanal atresia with absent/hypoplastic nipples, have occurred in infants born to mothers receiving methimazole therapy during pregnancy. The manufacturer recommends using the lowest dose possible if methimazole is used during pregnancy. If the patient becomes pregnant while taking the drug, the patient should be warned of the potential hazard to the fetus. Propylthiouracil is typically the preferred agent in pregnancy as is crosses the placenta to a lesser degree.
Methimazole Lactation Warnings
Methimazole is excreted into human milk. Methimazole is considered contraindicated during breast-feeding by the manufacturer.
In a controlled study involving 139 thyrotoxic lactating mothers and their infants, no deleterious effects were observed in thyroid function and physical and intellectual development of breastfed infants whose lactating mothers were treated with doses of methimazole up to 20 mg daily.
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