Very high dose of PTU (1,200 mg) per day

[Lactation Clinic]

Dear Dr.Hale,

A mother receives PTU(50mg) 6 tabs x 4 times a day = 1,200 mg per day. This is my first case who has a very high dose of PTU. I always follow the recommendation from Hale's Medications and Mothers' Milk, however, the very high dose of PTU like this case, I am hesitant to decide how to manage this case to continue breastfeeding. Please suggest. Thank you very much.

[kaytlin]

Hello again,

Good catch--doses are so important to evaluating safety. Current research indicates that patients taking up to 750 mg per day can breastfeed with infant monitoring. This research also showed that infant responses were not always dose-related. Other variables might include differences in infant absorption.

A 1,200 mg dose is concerning. I would suggest monitoring the infant's thyroid function every 2-3 months while exclusively breastfeeding.

Dr. Kaytlin Krutsch, PharmD


Momotani N, Yamashita R, Makino F, Noh JY, Ishikawa N, Ito K. Thyroid function in wholly breast-feeding infants whose mothers take high doses of propylthiouracil. Clin Endocrinol (Oxf). 2000;53(2):177-181. doi:10.1046/j.1365-2265.2000.01078.x

[Lactation Clinic]

Dear Dr. Krutsch,

Thank you so much for your valuable suggestion and all useful information.