Determination of plasma concentrations of d-norgestrel during a one year follow-up in women with a d-norgestrel-releasing IUD.

Eight healthy women had a d-norgestrel-releasing intrauterine device inserted postmenstrually and maintained in the uterine cavity for a one year period. Plasma concentrations of d-norgestrel were measured by radioimmunoassay during the one year treatment period. d-Norgestrel could be detected in the plasma of all the subjects within a fairly narrow range during the whole period. The release rate of d-norgestrel was calculated from two IUDs removed after the treatment.