Human maternal and fetal plasma glyceryl trinitrate concentrations

Objective This study was undertaken to determine the maternal and fetal steady-state concentrations of glyceryl trinitrate (GTN) and its dinitrate metabolites during transdermal administration, at the time of fetal blood sampling for obstetric indications. Study design Transdermal GTN (0.4 mg/h) was applied approximately 2 hours before investigative fetal blood sampling to maintain uterine quiescence. Serial maternal venous (MV) and a single fetal venous (FV) plasma samples were collected and assayed for GTN and its metabolites, 1,2- and 1,3-glyceryl dinitrate. Results The steady-state MV plasma concentration was 4.3±0.84 nmol/L (mean±SEM, n = 7), and the dinitrate metabolites were detectable in the MV but not quantifiable. GTN was detectable in the FV (n = 7) but was not quantifiable as the levels were less than the lower limit of sensitivity of the assay (<1 nmol/L). Conclusion During transdermal GTN administration, the steady-state FV/MV concentration ratio is less than 0.23 at the time of fetal blood sampling.