Ovarian function during use of vaginal rings delivering three different doses of Nestorone (R)

Contraceptive vaginal rings delivering various progestins alone or in combi nation with estrogen have been previously studied, showing adequate steroid vaginal absorption and acceptability by the users. Nestorone (R) progestin (NES) is a potent 19-nor-progesterone derivative, inactive by the oral rou te, but an excellent option for vaginal delivery. The purpose of this study was to evaluate ovarian function during 6 months of continuous use of prog estin-only vaginal rings delivering 3 different doses of NES: 50, 75, and 1 00 mug per day. Blood samples were taken twice a week for 5 consecutive wee ks during a control cycle and on months 1, 3 and 6 of use, for the measurem ent of estradiol (E2), progesterone (P), and NES, A total of 87 volunteers randomly received each of the 3 doses. After an initial peak, NES serum lev els remained fairly constant throughout the duration of the study at about 125, 200 and 250 pmol/L, respectively, decreasing slightly with time. Lutea l activity occurred very rarely (1.2-2.6% of sampling periods) with no appa rent difference between doses. Low E2 levels (less than or equal to 100 pmo l/L) in all samples of a run were rare (5%) and only with the high dose rin g (100 mug/day). E2 remained within normal levels (101-1500 pmol/L) in most of the segments studied. We conclude that the 50 and 75 mug/day NES rings provide adequate ovulation inhibition without hypoestrogenism, while the 10 0 mug/day ring may deliver an unnecessarily high dose. (C) 2001 Elsevier Sc ience Inc. All rights reserved.