Time-course of transplacental passage of diazepam: Influence of injection-delivery interval on neonatal drug concentrations.

Neonatal drug concentrations and neonate/mother concentration ratios are reported in 73 cases of elective Caesarean section and forceps deliveries where diazepam was used as an intravenous sleep-inducing agent. The various parameters were plotted against the injection-delivery interval and the correlation was tested using a non-parametric ranking method. The concentration of diazepam in mixed arteriovenous umbilical cord blood was negatively correlated with the injection-delivery interval in the range of 55 to 810 seconds. Statistically significant positive correlation (p less than 0.001) were found between the injection-delivery interval and the neonatal concentrations at 2 and 24 hours. The corresponding neonate/mother concentration ratios varied considerably, and were not so strongly correlated to the duration of antenatal drug transfer. The results suggest that with a slowly eliminated agent like diazepam, the drug concentration in capillary blood obtained from the newborn a few hours after delivery gives a reasonably good indication of the fetal drug exposure. The transplacental passage of diazepam is rapid, with distribution equilibrium between mother and fetus approached within 5 to 10 minutes after intravenous injection of the drug.