title: Human maternal and fetal plasma glyceryl trinitrate concentrations.
abstract: 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.
  
  
  METHODS
  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).
  
  
  CONCLUSIONS
  During transdermal GTN administration, the steady-state FV/MV concentration ratio is less than 0.23 at the time of fetal blood sampling.
authors.affiliation: Department of Pharmacology and Toxicology, Queen's University, Kingston General Hospital, 76 Stuart Street, Kingston, Ontario, Canada K7L 2V7.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Bustard
authors.forename: Greg
authors.initials: G
authors.lastname: Ryan
authors.forename: Gareth
authors.initials: G
authors.lastname: Seaward
authors.forename: Mary-Ellen
authors.initials: ME
authors.lastname: Saleniak
authors.forename: Graeme N
authors.initials: GN
authors.lastname: Smith
mesh_terms: D000279:Administration, Cutaneous; D001682:Biological Availability; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D005865:Gestational Age; D006801:Humans; D008431:Maternal-Fetal Exchange / Q000187:drug effects; D005996:Nitroglycerin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D007752:Obstetric Labor, Premature / Q000517:prevention & control; D011247:Pregnancy / Q000097:blood*; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D015149:Tocolytic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D015149:Tocolytic Agents; D005996:Nitroglycerin