Placental Transmission and Neonatal Metabolism of Promazine

Blood and urine analyses were conducted on pregnant and non-pregnant subjects who had each received 50 mg promazine intravenously. A typical exponential fall in the concentration of promazine in blood was observed. The obstetric patients were found to excrete, in a 24-hour sample of urine, considerably more promazine (and its primary metabolites) than did the non-obstetric subjects. Two neonates, who were given promazine intramuscularly, resembled the obstetric patients in the latter regard. Promazine could be identified in cord blood 2 minutes after intravenous administration to the mother, and a maximum level of concentration was reached 2–3 minutes later. Allowing for the influence of a “time-lag”, concentration in foetal blood was always lower than that in maternal blood. Results of the urine analyses suggested that approximately 0.5 per cent of the amount of promazine given intravenously to the mother reaches the foetus. A small amount of promazine is retained by placental tissue.