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The influence of dose-delivery time interval on neonatal plasma pethidine levels
Plasma pethidine levels were determined by RIA during the first 24h of life in 126 neonates whose mothers had received a single intramuscular dose of 100-150 mg pethidine HCl 0.25 to 19.5 h before delivery. The mean (geometric) maternal and cord venous plasma pethidine concentration and the neonatal capillary plasma levels at 0.5, 1.5 and 12-24 h expressed per unit dose were 125, 98, 71, 59 and 23 ng/ml per mg/kg respectively. The mean (+/- S.E.M.) cord: maternal plasma concentration ratio was 0.741 +/- 0.036 (n = 40). The ratio was significantly correlated with the dose-delivery interval, r = 0.42, p less than 0.01. The pethidine concentration in cord and in neonatal capillary plasma was significantly correlated to the weight related dose, r = 0.25 to 0.48, p less than 0.01. Cord venous levels of pethidine rose rapidly after drug administration but neonatal capillary levels increased slowly to reach peak levels at 2 to 5 h before declining over the next 15 to 18 h. The maternal plasma pethidine half-life, 5.59 h was considerably shorter than that observed in the newborn, 15.94 h.
Plasma pethidine levels were determined by RIA during the first 24h of life in 126 neonates whose mothers had received a single intramuscular dose of 100-150 mg pethidine HCl 0.25 to 19.5 h before delivery. The mean (geometric) maternal and cord venous plasma pethidine concentration and the neonatal capillary plasma levels at 0.5, 1.5 and 12-24 h expressed per unit dose were 125, 98, 71, 59 and 23 ng/ml per mg/kg respectively. The mean (+/- S.E.M.) cord: maternal plasma concentration ratio was 0.741 +/- 0.036 (n = 40). The ratio was significantly correlated with the dose-delivery interval, r = 0.42, p less than 0.01. The pethidine concentration in cord and in neonatal capillary plasma was significantly correlated to the weight related dose, r = 0.25 to 0.48, p less than 0.01. Cord venous levels of pethidine rose rapidly after drug administration but neonatal capillary levels increased slowly to reach peak levels at 2 to 5 h before declining over the next 15 to 18 h. The maternal plasma pethidine half-life, 5.59 h was considerably shorter than that observed in the newborn, 15.94 h.