Transfer of Zolpidem to Cord Blood and Breast Milk: A Case Series Evaluating Zolpidem Serum Levels and Outcomes in Birth and Suckling Infants

Background: Zolpidem is used for insomnia in pregnant and lactating women. Although zolpidem has been shown to cross the placenta and to be secreted into breast milk, it would not be expected to cause any adverse effects in newborn and breastfed infants. However, there is no relevant information on serum zolpidem levels in the newborn and breastfed infant from zolpidem-treated mother. This study aimed to present the outcomes of zolpidem exposure into infant who was delivered or breastfed by a zolpidem-treated mother. Methods: In this case series, zolpidem-treated pregnant women were recruited between September 2019 and April 2022, and maternal serum, cord blood, breast milk, and infants' serum were collected, and the zolpidem concentration in each sample was evaluated. Childbirth outcomes, including 1-month health care checkup, were also evaluated. Results: Three cases were recruited during investigation period. No spontaneous abortion or preterm live deliveries occurred. Oxygen intervention was required in one term infant, but the findings resolved on postpartum day 1. No medical intervention was required in other three infants. Zolpidem was not detected in infants' serum even after breastfeeding. There are no abnormal developmental findings in any of the infants in their 1-month health checkups. Conclusions: Zolpidem transferred into fetal circulation in utero and breast milk, however no harmful findings existed in infants during pregnancy and lactation. Exposure doses through breastfeeding is small, which may be a cause of rare detection from the infants' serum. Due to the limited number of cases, larger studies and integrated review are needed.