Placental transfer of dexamethasone in near-term sheep

The placental transfer of ³H-dexamethasone was studied in six near-term sheep. The placental clearance of ³H-dexamethasone was 18.8+-3.5 ml/min per kg of fetal weight. The clearance of dexamethasone by the fetal tissues was 9.3+-2.5 ml/min per kg and the degree of diffusion limitation to the placental transfer of dexamethasone was 78+-4%. The placental transfer of dexamethasone is therefore limited primarily by the nature of the placental barrier.