• E Weisberg, I S Fraser, M Lacarra, D R Mishell, F Alvarez, V Brache, and H A Nash.
• Sydney Centre for Reproductive Health Research, Family Planning NSW, Australia. eweisberg@s055.aone.net.au
• Contraception. 1999 May 1; 59 (5): 311-8.

AbstractA combined contraceptive vaginal ring designed to last 12 months was tested at three clinic sites. This ring released approximately 1 mg of norethindrone acetate (NET-Ac) and 20 micrograms of ethinyl estradiol (EE) daily. A total of 60 women were enrolled to use the ring in a schedule of 3 weeks in/1 week out. Serum norethindrone (NET) and ethinyl estradiol (EE) levels were assayed twice weekly in cycles 6, 9, and 13. Mean NET concentrations between cycles 6 and 9 were relatively stable between 13 and 19 nmol/L but showed a 10%-21% decrease in all centers between cycles 9 and 13. Mean EE concentrations ranged from 75 to 103 pmol/L, but did not have the same decrease as NET between cycles 9 and 13. Cycles with progesterone peaks (> 9.6 nmol/L) compatible with some luteal activity occurred in 4% of cycles sampled in Sydney, 3% in Santo Domingo, and 26% in Los Angeles. Half of these cycles exhibited at least one progesterone value > 32 nmol/L with three of 18 occurring in noncompliant cycles. Heavier body weight was associated with increased probability of luteal activity. Based on serum estradiol peaks > 400 pmol/L, eight of 81 cycles appeared to have marked follicular activity with no luteal activity. No pregnancies occurred. Nausea was reported by about half the subjects in approximately 10% of the visits (mainly in the first 1-2 days in the first cycle immediately after ring insertion). Vomiting was reported by 20% of subjects early in the first cycle only. Headache was reported on occasion by nearly 50% of the women, but the relationship to ring use was uncertain. Vaginal discharge was reported by 17 women (82% of these were from one clinic). Of 60 women, 14 discontinued before completing the study, but only two discontinuations were for medical reasons. Small but statistically significant changes occurred in lipid levels in two of the three centers. All changes remained within normal limits and were similar to those seen with many oral contraceptives. It appears that this ring may perform slightly differently in different populations, but is a highly satisfactory method of contraception for many women. Minor modifications in design could provide higher levels of steroid release and in the later months of the ring life span would assure continuing high levels of contraceptive protection for heavier women.

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