The ethynylestradiol concentration--in the presence of ethynodiol diacetate--in serum after oral administration was measured by a rapid radioimmunoassay method developed by the authors. It was found that the peak level was reached 1 h after administration, and even after 12 h a significant amount of free ethynylestradiol was present in the serum. The transfer of ethynylestradiol into the placenta was also studied in subjects who were 10-12 weeks pregnant. Placenta/serum quotients were calculated for the ethynylestradiol, and were found to increase in parallel with the dose of the drug administered, proving that an ethynylestradiol enrichment of the placenta occurred as early as 10-12 weeks of pregnancy.
PIP: The ethinyl estradiol concentration--in the presence of ethynodiol diacetate--in serum following oral administration was measured by a rapid radioimmunoassay method developed by the authors. It was found that the peak level was reached 1 hour after administration, and even after 12 hours, a significant amount of free ethinyl estradiol was present in the serum. The transfer of ethinyl estradiol into the placenta was also studied in subjects who were 10-12 weeks pregnant. Placenta serum quotients were calculated for the ethinyl estradiol, and were found to increase in parallel with the dose of the drug administered, proving that an ethinyl estradiol enrichment of the placenta occurred as early as 10-12 weeks of pregnancy.