320 Placental Transfer and Fetal Elimination of Morphine

Abstract

Placental transfer of morphine (M) was studied to determine: 1)the rate of transfer of M across the placenta; 2)the degree that the fetus is responsible for its own elimination of M; 3)the selective directional clearance of M across the placenta. We placed chronic catheters in the descending aorta and inferior vena cava (IVC) of six pregnant ewes and their fetuses, and into the uterine (UTV) and umbilical (UMV) veins. Electromagnetic flow transducers were placed around the common uterine (UTA) and umbilical (UMA) arteries. M was infused into the maternal IVC at 15.8 mg/hr until steady state conditions were achieved. UTA, UTV, UMA, UMV M concentrations and UTA and UMA blood flows were measured at 5 and 6 hours. The next day, M was infused into the fetal IVC at 3.28 mg/hr and the same procedure followed.RESULTS: Maternal Infusion- The rate of intrinsic loss of M by the mother was 15.73 mg/hr or 99.6% of the infusion rate. The rate of loss of M from the mother to the fetus was 0.06 mg/hr or 0.4% of the infusion rate. Fetal Infusion- The rate of intrinsic loss of M by the fetus was 2.44 mg/hr or 74.4% of the infusion rate. The rate of loss of M from the fetus to the mother was 0.84 mg/hr or 25.6% of the infusion rate. There was no significant difference between maternal to fetal (1386 ml/hr) and fetal to maternal (984 ml/hr) clearances of M. Thus, 1)the rate of M transfer from the mother to the fetus is low relative to the infusion rate and the fetus is not a significant route of elimination of M by the mother; 2)the fetus is primarily responsible for elimination of M entering it's circulation; and 3)there is no selective clearance of M across the placenta in either direction.Supported by NIH grants DA02280 and GM26691

DOI: 10.1203/00006450-198104001-00331

Cite this paper

@article{Cohen1981320PT, title={320 Placental Transfer and Fetal Elimination of Morphine}, author={Martin S Cohen and Lewis B. Sheiner and Leslie Z Benet and Abraham M. Rudolph}, journal={Pediatric Research}, year={1981}, volume={15}, pages={493-493} }