The Placental Transfer of Pancuronium and its Pharmacokinetics During Caesarian Section

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Abstract
The placental transfer of pancuronium and its pharmacokinetics were investigated in 33 pregnant women undergoing caesarean section. After a single intravenous injection of 60–100 μg/kg, the serum pancuronium concentration was measured (using a fluorimetric method) in serial samples of maternal blood and in umbilical arterial and venous blood obtained at the time of delivery. Detectable amounts of pancuronium were found in all foetal blood samples. The cord vein to maternal concentration ratio of pancuronium averaged 0.22; it increased significantly with prolongation of the induction‐delivery interval. The mean cord arterial to cord venous ratio of pancuronium was 0.66 (range 0.2–1.0), suggesting foetal drug uptake. Apgar scores were above 9 at 5 min in all cases, and there was no clinical evidence of any adverse effect in the newborns which could be related to the presence of a muscle relaxant.The distribution and elimination of pancuronium were compared in 18 normal subjects and in 21 women undergoing caesarean section. Plasma pancuronium concentration declined biexponentially with fast (α) and slow (β) phases, with half‐lives in the control group of 13 min and 146 min (mean values), respectively. In the women undergoing caesarean section, t 1/2 α was not changed, while t 1/2 β decreased slightly but significantly to 114 min.