Placental transfer of org nc 45 in women undergoing Caesarean section.

Org NC 45 60-80 microgram kg-1 was administered to 20 pregnant women undergoing general anaesthesia for Caesarean section. Org NC 45 plasma concentrations were measured fluorimetrically in samples of maternal, venous and arterial cord blood obtained at delivery. The venous cord to maternal concentration ratio averaged 11% and was not influenced by the interval between induction and delivery. The venous cord plasma concentration averaged 40 ng ml-1. The arterial cord concentration was less than the venous cord concentration in every instance and was undetectable in four patients. It is concluded that Org NC 45 crosses the human placental barrier to a very limited extent and that its use during anaesthesia for Caesarean section is safe for the newborn.