Propylthiouracil Pregnancy and Breast Feeding Warnings
Propylthiouracil is also known as:
Overview
Propylthiouracil 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 Propylthiouracil while you are pregnant. Propylthiouracil is found in breast milk. Do not breast-feed while taking Propylthiouracil .
Propylthiouracil Pregnancy Warnings
Propylthiouracil has been assigned to pregnancy category D by the FDA. There are no controlled data in human pregnancy. Reports of congenital anomalies attributed to propylthiouracil are lacking although neonatal hypothyroidism, goiter, and a case of neonatal hepatitis with use near term have been reported. While considered the drug of choice for hyperthyroidism during pregnancy, propylthiouracil is only recommended for use when benefit outweighs risk.
Propylthiouracil is known to cross the placenta. In one study, six hyperthyroid women were treated with propylthiouracil throughout pregnancy. Doses were withheld during labor and delivery. One to nine hours after the last dose of 100 to 150 mg, maternal propylthiouracil serum concentrations averaged 0.19 mcg/mL while cord blood concentrations averaged 0.36 mcg/mL. Pharmacokinetic evaluation suggested fetal clearance was slower than maternal clearance of propylthiouracil. To date, there is no evidence to support a teratogenic risk of propylthiouracil during pregnancy. However, mild hypothyroidism and neonatal goiter may occur. One review estimates a 12% incidence of propylthiouracil-induced neonatal goiter based on reported cases, although iodides were also used in some cases. As maternal hyperthyroidism may be associated with an increased risk of congenital anomalies, spontaneous abortion, prematurity, and perinatal death, medical and/or surgical intervention is usually indicated.
Propylthiouracil Lactation Warnings
Propylthiouracil is excreted into human milk in small amounts. While adverse effects in the nursing infant are not reported, the manufacturer considers propylthiouracil to be contraindicated during lactation. However, propylthiouracil is considered compatible with breast-feeding by the American Academy of Pediatrics.
The excretion of propylthiouracil into breast milk was studied in one women, following oral administration of 35-S propylthiouracil 100 mg (100 uCi). The milk to plasma concentration ratio for unbound drug averaged 0.55 and remained fairly constant. Only 0.077% of the administered dose of radioactivity was excreted into milk over a 24-hour collection period. In another study, the peak concentrations in milk and maternal serum occurred at 90 minutes post-dose and averaged 0.7 and 7.7 mcg/mL, respectively. The mean total amount of propylthiouracil excreted into milk over the 4-hour study period was 99 mcg, or 0.025% of the administered dose. In addition, the authors followed for five months one breast-feeding infant whose mother was treated with 200 to 300 mg propylthiouracil per day. No changes in the infant's serum thyroxine, triiodothyronine, TSH, or T3-resin-uptake were observed during this time.
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