Transplacental transfer and metabolism of 17-α-hydroxyprogesterone caproate

Objective: Determine transplacental transfer and metabolism of 17-α-hydroxyprogesterone caproate and its distribution between the tissue and the maternal and fetal circuits of the dually perfused placental lobule. Study Design: 17-α-Hydroxyprogesterone caproate (21 ng/mL) and its dual-labeled isotope, 17-α-hydroxy-[³H] progesterone [¹⁴C] caproate were added to the maternal circuit. The concentrations of the drug and its metabolite in trophoblast tissue and both circuits were determined by high performance liquid chromatography and liquid scintillation spectrometry. Results: 17-α-Hydroxyprogesterone caproate was transferred from the maternal to fetal circuit. After a 4-hour perfusion period, a metabolite of 17-α-hydroxyprogesterone caproate that retained both progesterone and caproate moieties was identified in the tissue and the maternal and fetal circuits. Neither 17-α-hydroxyprogesterone caproate nor its metabolite, at the concentrations tested, had adverse effect on determined viability and functional parameters of placental tissue. Conclusion: 17-α-Hydroxyprogesterone caproate was metabolized by term placental lobule during its perfusion and both parent compound and its metabolite(s) transferred to the fetal circuit.