The transfer of diazepam across the placenta during labour.

The transfer of diazepam through the placenta during labour was studied by the gas chromatographic method developed by us using a Ni⁶³-electron capture detector. 10 mg of diazepam was given intramuscularly to 37 patients during the first stage of labour 5-401 min before delivery, after which blood samples were immediately collected from the umbilical cord and the maternal vein. Diazepam was found in all the plasma samples with very great individual variation in the concentrations. In one particular case, in which the delivery took place 5 minutes after the diazepam injection, the corresponding diazepam concentrations in the cord plasma and in the maternal plasma were 506 ng/ml and 504 ng/ml. In 31 cord plasma samples collected 26-401 min after the diazepam injection the mean diazepam concentration was 70 ng/ml, and in the maternal plasma was 38 ng/ml. The average foetal/maternal concentration ratio during the same time period was 2.0 and in the whole series 1.8. Neither the diazepam concentrations in the cord plasma nor the foetal/maternal ratios of the concentrations had any significant influence on the Apgar scores of the newborns. The cause of the diazepam accumulation in the foetal circulation is unclear. The better binding of diazepam with the foetal plasma proteins is discussed. The importance of individual drug doses to parturients according to their weight is emphasized. [ABSTRACT FROM AUTHOR]