A clinical pharmacological study of a new type of vaginal delivery system for levonorgestrel

The pharmacokinetic and pharmacodynamic effects of a new type of levonorgestrel-releasing vaginal device (with an in vitro release rate of 25 micrograms/24 h) were studied in a group of 18 normally menstruating women during a period of 90 days of continuous use. Peripheral blood samples were drawn three times weekly (Mondays, Wednesdays, Fridays) during a pretreatment (control) cycle and during the 90 days (3 segments) of exposure to levonorgestrel and the levels of levonorgestrel, progesterone and estradiol were analyzed. Blood samples were also drawn at frequent intervals during the first day and daily during the first week with the devices in situ. In addition, endometrial biopsy specimens were obtained during days 20-22 of the control cycle and then 6 and 10 weeks following the insertion of the devices for morphometric analysis and for the assay of progesterone and estradiol levels. Following insertion of the devices, plasma levels rapidly rose to 1 nmol/l in 12 hours; a plateau of approximately 1.6 nmol/l was reached in 3-4 days, after which the plasma levels declined in a linear fashion with a daily average rate of 7.4 pmol/l to 60% of the initial level in 90 days' time. Of the 54 treatment segments of 30 days, 68% were anovulatory and 24% showed normal, ovulatory-like estradiol and progesterone levels. A complete set of three biopsies were obtained from 15 of the 18 subjects. Of the biopsies obtained during exposure to levonorgestrel only one exhibited signs of atrophy, 80% showed suppressed or arrested proliferation, and 10% had a normal cyclic appearance.(ABSTRACT TRUNCATED AT 250 WORDS)