Sustained intrauterine release of d-norgestrel.

Clinical experience with seventy-two first insertions of a d-norgestrel-releasing IUD is reported. Plasma d-norgestrel concentrations were measured in twelve subjects. No pregnancies occurred in the 522 woman-months of use (averaging 7.3 months/subject) that have been accumulated. Removals were performed in six subjects for medical reasons and in seven subjects for personal reasons. Plasma concentrations of d-norgestrel were highest during the first two weeks of use. A decline in the plasma concentration of d-norgestrel occurred and was only 0.05 ng/ml between 30 and 90 days after insertion.