Antenatal pharmacokinetics and placental transfer of N-acetylcysteine in chorioamnionitis for fetal neuroprotection.

Objective To determine the pharmacokinetics (PK) and placental transfer of intravenous (IV) N -acetylcysteine (NAC) in mothers with a clinical diagnosis of chorioamnionitis (CA) and determine the PK of IV NAC in their infants. Study design In this prospective, double-blind study IV NAC 100 mg/kg/dose or saline was administered within 4 hours of CA diagnosis to pregnant women ≥24 weeks' gestation and then every 6 hours until delivery. Maternal PK and placental transfer were determined with maternal blood and matched maternal and cord venous blood. Neonatal PK estimates were determined from IV NAC (12.5-25 mg/kg/dose) administered every 12 hours for 5 doses. Noncompartmental analyses were performed for maternal and neonatal PK estimates. Results Eleven mothers (5 preterm, 6 near-term) and 12 infants (1 set of twins) received NAC. Maternal clearance (CL) of NAC was faster than in nonpregnant adults, with a terminal elimination half-life of 1.2 ± 0.2 hours. The NAC cord to maternal ratio was 1.4 ± 0.8, suggesting rapid placental transfer and slower rate of fetal CL. Neonatal PK estimates for near-term compared with preterm infants showed a significantly shorter terminal elimination half-life (5.1 vs 7.5 hours, respectively) and greater CL (53.7 vs 45.0 mL/h/kg, respectively). Conclusions Maternal CL and placental transfer of NAC was rapid, with umbilical cord concentrations frequently exceeding maternal concentrations. The administration of NAC to mothers with CA achieves predictable NAC plasma concentrations in the fetus, indicating that antenatal neuroprotection may be possible for these newborns at high risk for neuroinflammation.