Umbilical Cord Monitoring of In Utero Drug Exposure to Buprenorphine and Correlation with Maternal Dose and Neonatal Outcomes
Buprenorphine is under investigation in the U.S. as pharmacotherapy for opioid-dependent pregnant women. Buprenorphine and metabolites were quantified in umbilical cord specimens from women receiving daily buprenorphine doses. Correlations between maternal buprenorphine dose, buprenorphine and metabolite umbilical cord concentrations, and neonatal outcomes were investigated, as well as the ability to identify heroin and cocaine relapse during pregnancy. Umbilical cord concentrations were compared to those of matched umbilical cord plasma and meconium. Buprenorphine metabolites were detected in all cords, but buprenorphine itself was absent. Concentration ranges were 1.2-5.1 ng/g norbuprenorphine, 1.7-4.2 ng/g buprenorphine-glucuronide, and 8.3-23 ng/g norbuprenorphine-glucuronide. Cord concentrations were similar to those in plasma, and lower (16-210-fold), although statistically correlated, than those in meconium. Significant positive correlations were observed for buprenorphine-glucuronide concentrations in umbilical cord and mean maternal BUP daily dose throughout pregnancy and third trimester, but buprenorphine biomarker concentrations did not predict neonatal outcomes. Opiate concentrations were lower (200-fold) in umbilical cord than in meconium, and when cocaine was present in meconium, it was not identified in cord. Umbilical cord can serve as an alternative matrix for identifying prenatal drug-exposure, but is much less sensitive than meconium. Buprenorphine provided a controlled drug administration model for evaluating drug disposition in the maternal-fetal dyad.