Ovarian function with a novel combined contraceptive vaginal ring

Titia M.T. Mulders1, Thom O.M. Dieben1,3 and Herjan J.T.Coelingh Bennink2

1 Clinical Development Department, NV Organon, Oss, The Netherlands and 2 Centre for Reproductive Medicine, Academic Hospital V.U.B., Laarbeeklaan 101, B-1090 Brussels, Belgium


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
BACKGROUND: NuvaRing® is a combined contraceptive vaginal ring designed for 3 weeks continuous use followed by a 1 week ring-free period. The present study evaluated ovarian function in women who were instructed to either adhere to, or deviate from, the recommended regimen of use. METHODS: In this open-label, randomized study, 45 women aged between 18 and 35 years used NuvaRing for one cycle in which the ring was used according to the recommended regimen. Women in group A (n = 15) then continued with a ‘normal’ 3 week period of ring use after which the restoration of ovarian function—i.e. the time to ovulation—for each woman was determined by daily vaginal ultrasound and serum hormone levels. For women in group B (n = 15), the second cycle consisted of only 3 consecutive days of ring use, after which each woman was monitored until ovulation. Women in group C (n = 15) were not permitted to start a second ‘normal’ cycle until a follicle with a diameter of 13 mm was observed by vaginal ultrasound; subsequently, the development of these follicles during the second cycle of ring use was monitored daily. RESULTS: Irrespective of the length of the second cycle, 3 weeks (group A) versus 3 days (group B), a new cohort of follicles needed to be recruited and the time to ovulation after ring removal was similar (19 versus 17 days). The median time needed to develop a follicle up to 13 mm in diameter (group C) was 11 days (range 8–21 days); none of the women ovulated after insertion of the second ring. CONCLUSION: NuvaRing is a highly effective, reversible method of hormonal contraception. Ovulation, at least until the stage of a 13 mm dominant follicle, is prevented and as little as 3 consecutive days of NuvaRing use interferes with follicle growth.

Key words: compliance/etonogestrel/ovarian function/vaginal ring


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
NuvaRing® (NV Organon) is a combined contraceptive vaginal ring containing etonogestrel (ENG) and ethinyl estradiol (EE). ENG is the biologically active metabolite of desogestrel. Each ring releases an average of 120 µg ENG and 15 µg EE per day and is designed for one cycle, comprising 3 weeks of continuous use followed by a 1 week ring-free period. NuvaRing is a flexible, soft, transparent ring with an outer diameter of 54 mm and a cross-section of 4 mm, that can be easily inserted and removed by the woman herself.

The pharmacokinetics and pharmacodynamics—i.e. interference with follicle development and inhibition of ovulation—of NuvaRing have been studied during normal and prolonged use, where the ring was left in place for an additional 2 weeks. This study showed controlled release concentration–time profiles for ENG and EE (Timmer and Mulders, 2000Go). Using NuvaRing for the recommended period of use resulted in complete inhibition of ovulation, as assessed by vaginal ultrasound and serum concentrations of FSH, 17ß-estradiol (E2), LH and progesterone. Inhibition of ovulation was maintained during the additional 2 week period of NuvaRing use (Mulders and Dieben, 2001Go).

As with any contraceptive method, compliance with the prescribed regimen is essential to maintain reliability. The aim of the present study was to test the robustness of this novel form of contraception if the usage schedule was deviated from. This was done by evaluating ovarian function with NuvaRing in women who were instructed either to adhere to, or to deviate from, the recommended regimen of use.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
This open-label, randomized, pharmacodynamic study was conducted at the Kendle Clinical Pharmacology Unit in Utrecht, The Netherlands between January 1999 and June 1999. The study was conducted in accordance with the Declaration of Helsinki, the International Committee for Harmonisation for Good Clinical Practice and current regulatory guidelines. The study protocol was approved by the Institutional Review Board of the Academic Hospital in Utrecht, The Netherlands, and all subjects entering the trial provided written informed consent.

Study population
Fifty-one women, aged 18–35 years, in good physical and mental health and with a body mass index (BMI) between 18 and 29 kg/m2 were enrolled into the study. All subjects were required to have good visibility of both ovaries by vaginal ultrasound and good venous accessibility. Subjects were excluded if they had any contraindications to contraceptive steroids. Other exclusion criteria specific to vaginal ring use comprised: the presence at screening of a cervicitis, vaginitis or a bleeding cervical erosion; diagnosis at screening of a Papanicolaou (PAP) Class III, IV or V cervical smear result; cystocele, rectocele or prolapse of uterine cervix; severe or chronic constipation; dyspareunia or other coital problems.

Study design
All trial medication was supplied by NV Organon, Oss, The Netherlands. All subjects received at least one pretreatment cycle of a combined oral contraceptive (COC) containing 150 µg desogestrel and 30 µg EE (Marvelon®; NV Organon). Following the usual 7 day pill-free period, all women were randomly allocated to one of three treatment groups, A–C (Figure 1Go). The women were assigned to one of the groups and given a subject code number according to a randomization list. Forty-five women used NuvaRing according to the recommended regimen of use (3 weeks of continuous ring use followed by a 1 week ring-free interval) for the first cycle. The second cycle differed depending on the treatment group (15 women per group). Six randomized subjects did not receive NuvaRing treatment but were held in reserve in case there were drop-outs.



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Figure 1. Treatment schedule for each of the three groups. Treatment periods are in bold boxes; ring-free periods are in fine boxes. In group C, the first ring-free period extended until a 13 mm follicle was detected by ultrasound.

 
Women in group A used NuvaRing according to the recommended regimen in the second cycle, after which restoration of ovarian function for each subject was determined by vaginal ultrasound and serum hormone levels. The second cycle for women in group B consisted of only 3 consecutive days of ring use, after which each woman was monitored until ovulation. Women in group C were not permitted to start a second normal cycle until a follicle of 13 mm was observed. The development of these follicles during the second cycle of ring use was then followed by ultrasonography.

Before the start of the first treatment cycle, women were instructed how to insert and remove the ring. Temporary ring removal was not allowed and condoms were used as additional protection against pregnancy if follicles with a diameter >=13 mm were observed during the vaginal ultrasound assessments.

Study assessments
At screening, all subjects provided a medical and gynaecological history and underwent a medical and gynaecological examination. Immediately before insertion of the first vaginal ring, a home pregnancy test was performed. NuvaRing treatment was only started if this test was negative.

Vaginal ultrasonography was performed and blood samples were collected for assay of serum hormones according to the following schedule. (i) Group A (3 week cycle): on day 21 of the second cycle and daily thereafter until the detection of ovulation by vaginal ultrasound. Maximal follow-up period was 28 days following ring removal. After ovulation, daily blood sampling continued for an additional period of 7 days, but never beyond the maximum period of follow-up. (ii) Group B (3 day cycle): on the first, second (ultrasound only), and third day of the second cycle (3 day cycle), and daily thereafter until the detection of ovulation by vaginal ultrasound. Maximal follow-up period was 28 days following ring removal. After ovulation, daily blood sampling continued for an additional period of 7 days, but never beyond the maximum period of follow-up. (iii) Group C (13 mm follicle): on day 21 of the first cycle and daily thereafter up to and including the day of removal of the second vaginal ring.

Vaginal ultrasonography was performed using a Toshiba Capasse SSA-220A with a 5 MHz transvaginal transducer. Follicle size was determined based on the measurement of follicular diameters (measured in the longitudinal and transverse planes). The mean of the two axes was to be recorded. Only follicles with a diameter >=5 mm were recorded. Endometrial thickness was measured by vaginal ultrasound of the sagittal plane of the uterus and calculated by measuring the sum of both endometrial layers.

Blood samples were processed to serum and stored at –20°C until assays were performed. FSH, E2, LH, and progesterone levels in serum were determined by time-resolved fluoroimmunoassay (AutoDelfia®; Wallac Oy, Turku, Finland). Samples from one subject were analysed in one series (one batch) as much as possible. The inter-assay precision for FSH, E2, LH, and progesterone varied from 1.9 to 6.4%. The intra-assay precision varied from 0.9 to 6.5%.

During the whole study period, women recorded compliance to the NuvaRing treatment schedule on diary cards. Compliance was documented as the number of hours of ring use per day. Questioning regarding the occurrence of adverse events and use of concomitant medication took place throughout the trial. In addition to medications known to interfere with the effect of sex steroids, concomitant use of sex steroids other than the trial medication was prohibited. After completion of the study, women underwent a physical and gynaecological examination.

Statistical methods
The sample size of 15 subjects per treatment arm was justified by sufficiently narrow confidence intervals for the mean time to ovulation (groups A and B) and for the relative frequency of non-ovulating subjects (group C), taking into account a 20% discontinuation rate (i.e. three subjects) per treatment arm.

Summary statistics (median with interquartile ranges) were calculated for vaginal ultrasound measurements (follicular diameters and endometrial thickness) and serum hormone levels. The median values and ranges as presented apply to the diameters of the largest follicles or the highest serum hormone levels per subject per day. Summary statistics (mean, median, minimum and maximum) were also calculated for the time to ovulation and the time to detection of the largest follicle (in groups A and B), or the time needed to develop a follicle with a diameter of 13 mm (group C). The exposure data were summarized for each treatment group by listing the total hours of NuvaRing use. The tolerability analyses were restricted to descriptive statistics.


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
Patient characteristics
A total of 45 women used NuvaRing; each treatment group consisted of 15 subjects. There were no relevant differences between the three groups in baseline demographic characteristics (Table I). The physical and gynaecological examinations revealed no abnormalities and all pregnancy tests were negative.


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Table I. Baseline demographics in groups A (3 week cycle), B (3 day cycle) and C (ring-free until 13 mm follicle)
 
The NuvaRing treatment regimen scheduled by the protocol was correctly followed by all women except one in group B, who inserted the second ring after a ring-free period of 6 instead of 7 days. One subject in group A discontinued the trial 1 day after removal of the second ring because of a sinusitis judged unrelated to NuvaRing. It was decided not to replace this woman.

Ovarian function
The pattern of restoration of ovarian function after using NuvaRing according to the recommended regimen (group A) or for 3 consecutive days only (group B) is displayed in Figures 2–4GoGoGo.



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Figure 2. Maximal follicular diameter and serum FSH levels after removal of the second ring in (a) group A (3 week cycle), and (b) group B (3 day cycle). Day 0 is day of ring removal. Values are median ± interquartile range.

 


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Figure 3. Maximal luteinizing hormone and progesterone levels after removal of the second ring in (a) group A (3 week cycle), and (b) group B (3 day cycle). Day 0 is day of ring removal. Values are median ± interquartile range.

 


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Figure 4. Maximal endometrial thickness and serum estradiol levels after removal of the second ring in (a) group A (3 week cycle), and (b) group B (3 day cycle). Day 0 is day of ring removal. Values are median ± interquartile range.

 
Immediately after removing the second ring, FSH levels rose, with peak levels occurring after 3 (group A) and 4 (group B) days. FSH levels subsequently decreased slowly with time. The LH surge occurred around 17 (group A) and 16 (group B) days following ring removal. The accompanying rise in FSH levels was also apparent around these days (after 18 days in group A and 17 days in group B).

In group A, follicle growth started 3 days after ring removal, increasing from a median maximum follicular diameter <=5 mm after ring removal to 18 mm at the time of the LH surge. In group B, follicle growth started 7 days after ring removal, increasing from a median maximum follicular diameter of 9 mm after ring removal to 19 mm at the time of the LH surge.

Concomitant with follicle growth, serum E2 levels started to rise 3 (group A) and 2 (group B) days after ring removal, with peak levels occurring around the time of LH surge. The endometrial thickness in women of group A decreased after removal of the ring (withdrawal bleeding), followed by growth from ~2 mm on day 5 to 10 mm at the time of LH surge. The endometrial thickness in women of group B also increased from day 5 onwards.

Vaginal ultrasound assessments showed that post-treatment ovulation occurred, within the maximum period of follow-up of 28 days, in 27 of 29 women in groups A and B. In both groups, ovulation was confirmed by adequately high serum progesterone levels in the luteal phase. The median time to ovulation was 19 (group A) and 17 days (group B) after removing the ring (Table IIGo), with the first ovulation occurring after 13 (group A) and 12 (group B) days.


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Table II. Time to ovulation after removing the second vaginal ring in groups A (3 week cycle) and B (3 day cycle), and time to develop a 13 mm follicle during an extended ring-free period between two NuvaRing treatments in group C
 
Women in group C did not insert the second NuvaRing until the vaginal ultrasound assessment indicated the presence of a follicle with a diameter of 13 mm; the median time for this to occur was 11 days (range 8–21 days; Table IIGo), i.e. 50% of the women needed an extension of the ‘normal’ ring-free period of >=4 days. None of the women in this group ovulated during the second treatment cycle.

In group C (Figures 5 and 6GoGo), the pattern of ovarian function in the ring-free period of the first cycle resembled that of group A after removal of the second ring (Figures 2–4GoGoGo). Ring removal resulted in a rise in FSH levels and accompanying stimulation of follicle growth, as evidenced by the increase in follicular diameters and serum E2 levels. Please note that (of course) in Figure 5Go the sample size decreases over time.



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Figure 5. Vaginal ultrasound measurements and serum hormone levels during the ring-free period (extended until follicular diameter >=13 mm) of the first NuvaRing treatment cycle in group C. Day 0 is day of ring removal. Values are median ± interquartile range.

 


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Figure 6. Vaginal ultrasound measurements and serum hormone levels during the second NuvaRing treatment period in group C (after the extended ring-free period). Day 1 is first day of ring use. Values are median ± interquartile range.

 
After 7 ring-free days, equivalent to the standard ring-free period, the median follicular diameter in group C was 8 mm (range: 5.2–10.6 mm); this is similar to that found 1 week after ring removal in group A (median 7.2 mm). Furthermore, women in group A needed ~12 days for a follicle with a diameter of 13 mm to develop. This is comparable with the 11 days noted for women of group C.

Insertion of NuvaRing after the extended ring-free period by women in group C interfered with ovarian function, as shown by the difference in patterns between Figure 6Go (group C) and Figures 2–4GoGoGo (group A). Follicle growth was disrupted as the median diameter of the largest follicle remained ~13–14 mm during days 1–11 of the second cycle, and serum E2 levels decreased after insertion of the second ring. Individually, an equal number of subjects showed an increase, a decrease or no change in the size of the largest follicle during the first week of the second cycle. The highest serum E2 levels were achieved during the extended ring-free period in all women except three with highest levels in the first week of the second cycle and one with the highest level on day 9 of the second cycle. These four women all had follicles that grew in the first half of the second cycle.

The inhibition of ovulation in group C demonstrated by vaginal ultrasound was confirmed by the absence of an LH surge and by low progesterone levels, during both the extended ring-free period of the first cycle and the normal ring-use period of the second cycle.

Tolerability
Twenty of the 45 subjects had drug-related adverse events (AEs). Most of these were classified as ‘female reproductive disorders’ and within this group ‘leukorrhoea’ and ‘dysmenorrhoea’ were most frequently reported. All cases of leukorrhoea concerned increased vaginal discharge. All reported adverse events were of mild-to-moderate intensity.

Results of the physical and gynaecological examinations and the haematology and blood biochemistry analyses performed at baseline and at the end of the study were comparable (data not shown).


    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
NuvaRing is a novel combined contraceptive vaginal ring that releases ENG and EE at a continuous daily rate of 120 and 15 µg respectively. This contraceptive ring is designed for use during one cycle, comprising a 3 week period of continuous use followed by a 1 week ring-free period. The present study assessed ovarian function with NuvaRing in women who were instructed to adhere to, or deviate from, the recommended regimen of use.

Irrespective of whether the length of the second NuvaRing treatment period was 3 days or the normal 3 weeks, ovulation required a similar time period after removal of the ring. The median time to ovulation after 3 days or 3 weeks NuvaRing use was 17 and 19 days respectively; the time for the first women to ovulate was also similar for these groups (12 and 13 days respectively). Although as a result of the different period of ovarian suppression the size of the follicles on the removal day was larger after 3 days compared with 3 weeks of NuvaRing exposure, the similarity in the time to ovulation in the two treatment groups shows that women in both groups needed to recruit a new cohort of follicles. Therefore, this study indicates that as little as 3 days of NuvaRing use is sufficient to suppress the hypothalamic–pituitary–ovarian axis, in contrast to the generally acknowledged requirement of 7 days with combined oral contraceptives (Guillebaud, 1987Go; Korver et al., 1995Go).

The median time needed for the development of a 13 mm follicle was 11 days, meaning that the standard ring-free period had to be extended by >=4 days to achieve this diameter in 50% of the women. The most rapid development of a 13 mm follicle required an extension of the ring-free period by only 1 day, whereas the slowest required a ring-free period of 21 days for the development of such a follicle. Since none of these women ovulated after inserting the second ring, these data indicate that ovulation of follicles with a size up to 13mm can be blocked by NuvaRing treatment.

The NuvaRing data (on extension of the ring-free period, group C) are in agreement with results from studies with several COC. Extension of the pill-free period by 3–4 days was associated with a large inter-individual variation in follicle growth, combined with a low risk of ovulation (Killick, 1989Go; Killick et al., 1990Go; Landgren and Csemiczky, 1991Go; Hedon et al., 1992Go; Elomaa et al., 1998Go). In one study (Killick 1989Go), the pill-free period was extended until follicles reached a diameter of 12 mm. The median pill-free period needed for development of such a follicle was 11 days (range: 7–16 days). Despite resumption of COC intake, most follicles continued to grow, and even responded to hCG administration by both rupture and luteinization. These data show that dominant follicles maintain the capacity to ovulate after exposure to contraceptive steroids. It is most likely that ovulation does not occur due to prevention of the LH surge by the combined contraceptive.

In a similar study (Elomaa and Lähteenmäki, 1999Go), follicles were allowed to continue to grow to a diameter of 16 mm before the start of the next pill cycle. As expected, the median time for the development of 16 mm follicles was greater (18 days; range: 14–26 days) than that for a 12 or 13 mm follicle. However, the ovulatory potential of a 16 mm functional follicle was not inhibited by the resumption of pill intake. This illustrates that only a substantial extension of the pill-free period may reduce the efficacy of combined contraceptives.

In conclusion, this study demonstrates that ovulation, at least until the stage of a 13 mm dominant follicle, is prevented and 3 consecutive days of NuvaRing use already interfered with follicle growth. In the meantime, large efficacy studies have demonstrated that NuvaRing (standard usage regimen of 3 weeks of continuous use followed by a 1 week ring-free period) is a highly effective, reversible method of hormonal contraception (Roumen et al., 2001Go). The results of the current study support this and show that NuvaRing remained a robustly effective method of contraception after some deliberate deviations from the standard usage regimen, provided that users adhered to the recommended regimen in the previous or subsequent cycle.


    Acknowledgements
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
We are grateful to T.Haring, MD (principal investigator) and H.Tennekes-Veldhuizen (ultrasound technician) of the Kendle Clinical Pharmacology Unit (Utrecht, The Netherlands) for their contribution to this study.


    Notes
 
3 To whom correspondence should be addressed at: Clinical Development Department, NV Organon, P.O.Box 20, 5340 BH Oss, The Netherlands. E-mail: thom.dieben{at}organon.com Back


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 Acknowledgements
 References
 
Elomaa, K. and Lähteenmäki, P. (1999) Ovulatory potential of preovulatory sized follicles during oral contraceptive treatment. Contraception, 60, 275–279.[ISI][Medline]

Elomaa, K., Rolland, R., Brosens, I., Moorrees, M., Deprest, J., Tuominen, J. and Lähteenmäki, P. (1998) Omitting the first oral contraceptive pills of the cycle does not automatically lead to ovulation. Am. J. Obstet. Gynecol., 179, 41–46.[ISI][Medline]

Guillebaud, J. (1987) The forgotten pill—and the paramount importance of the pill-free week. Br. J. Fam. Plann., 12, 35–43.

Hedon, B., Christol, P., Plauchut, A., Vallon, A.M., Desachampts, F., Taillant, M.L., Mares, P., Pizelle, A.M., Laffargue, F. and Viala, J.L. (1992) Ovarian consequences of the transient interruption of combined oral contraceptives. Int. J. Fertil., 37, 270–276.[ISI][Medline]

Killick, S.R. (1989) Ovarian follicles during oral contraceptive cycles: their potential for ovulation. Fertil. Steril., 52, 580–582.[ISI][Medline]

Killick, S.R., Bancroft, K., Oelbaum, J. et al. (1990) Extending the duration of the pill-free interval during combined oral contraception. Adv. Contracept., 6, 333–340.

Korver, T., Goorissen, E. and Guillebaud, J. (1995) The combined oral contraceptive pill: what advice should we give when tablets are missed? Br. J. Obstet. Gynaecol., 102, 601–607.[ISI][Medline]

Landgren, B. and Csemiczky, G. (1991) The effect of follicle growth and luteal function of ‘missing the pill’. A comparison between a monophasic and a triphasic combined oral contraceptive. Contraception, 43, 149–159.[ISI][Medline]

Mulders, T.M.T. and Dieben, T.O.M. (2001) Use of the novel combined contraceptive vaginal ring NuvaRing for ovulation inhibition. Fertil. Steril., 75, 865–870.[ISI][Medline]

Roumen, F.J.M.E., Apter, D., Mulders, T.M.T. and Dieben, T.O.M. (2001) Efficacy, tolerability and acceptability of a novel contraceptive vaginal ring releasing etonogestrel and ethinyl estradiol. Hum. Reprod., 16, 469–475.[Abstract/Free Full Text]

Timmer, C.J. and Mulders, T.M. (2000) Pharmacokinetics of etonogestrel and ethinylestradiol released from a combined contraceptive vaginal ring. Clin. Pharmacokinet., 39, 232–242.

Submitted on October 5, 2001; resubmitted on February 22, 2002; accepted on May 14, 2002.