Q: 28 year old female, admitted to ICU with Urosepsis. Patient routine screening becomes positive for pregnancy. Patient was unaware of it. Her list of medications include methimazole for her hyperthyroidism. What would be your next step?


Answer:

If pregnancy occurs while taking methimazole, switching to propylthiouracil (PTU) is suggested, particularly in first trimester.

Both PTU and methimazole are classified as Drug Class D in pregnancy. PTU is preferred over methimazole in the first trimester of pregnancy. In the second and third trimester, methimazole is preferred.



References:

1. Bahn RS, Burch HS, Cooper DS, et al. (July 2009). The Role of Propylthiouracil in the Management of Graves' Disease in Adults: report of a meeting jointly sponsored by the American Thyroid Association and the Food and Drug Administration . Thyroid 19 (7): 673–4.

2. Abalovich M, Amino N, Barbour LA, et al. (August 2007). Management of thyroid dysfunction during pregnancy and postpartum: an Endocrine Society Clinical Practice Guideline . J. Clin. Endocrinol. Metab. 92 (8 Suppl): S1–47