Effects of a single contraceptive Silastic implant containing nomegestrol acetate on ovarian function and cervical mucus production during 2 years

Abstract

Objective: To study the mechanism of action of Uniplant (South to South Corporation in Reproductive Health, Salvador, Brazil), a single Silastic capsule containing nomegestrol acetate (Lutenyl, Theramex, France) in women during 2 years.

Design: Comparison between the hormonal levels, follicular development, cervical mucus (CM) production, and endometrial thickness in the menstrual cycle before implant insertion and at 1, 6, 12, 18, and 24 months after implant insertion.

Participants: A total of 15 women of reproductive age were enrolled for the 1st year of use. Twelve of these women continued for a 2nd year of Uniplant use.

Main outcome measures: Hormonal plasma levels were measured in control cycles and at 1, 6, 12, 18, and 24 months of Uniplant use. Cervical mucus, follicular development, and endometrial thickness also were evaluated.

Results: In this study, Uniplant blocks ovulation in 86 percent of cycles studied. Disturbances in follicular growth were observed also. Cervical mucus was scanty and viscous in all women during this study. Endometrial thickness was <8 mm in all cycles studied.

Conclusion: This study shows that Uniplant is a long-acting contraceptive that probably acts at the hypothalamic-pituitary levels, on the ovary, on CM production, and on the endometrium. These properties suggest the use of Uniplant as a contraceptive agent, especially if one considers the lack of androgenic and metabolic effects and the maintenance of periodic bleeding similar to menstruation.

PIP: A total of 15 healthy women volunteers were enrolled in this study. Their mean age was 23 +or- 1.2 years (range, 18-33 years), mean weight was 55.7 +or- 2.6 kg (range, 40-72 kg), and mean parity was 1.1 (range, 0-4). Venous blood samples were drawn every other day from day eight of the cycle until sonographic evidence of a 12-mm follicle, and then every day until sonographic evidence of follicular rupture and thereafter every other day until the next menstrual bleeding. The capsules were removed at the end of one year of Uniplant use, and a new capsule was inserted in 12 subjects. The blood samples for hormonal analyses were taken after 18 and 24 months of Uniplant use in the 12 women who continued in the study. Levels of luteinizing hormone (LH) were significantly lower than in the control cycles during the observation period (p .01, p .05). According to transvaginal sonography, four different patterns of follicular development were found: normal follicular growth and rupture, persistent follicle, follicular cysts, and no follicular growth. Follicular growth and rupture were observed in 20% of the treated cycles. Persistent follicles were present in approximately 15% of the treated cycles. Follicular cysts were observed in 29% of the cycles studied during 24 months of Uniplant use. All subjects had normal cervical cytology before starting treatment, after 12 months, and after 24 months of Uniplant use. The maximum cervical mucus score for pretreatment cycles was 12.8 +or- 0.4. Endometrial thickness was 8 mm in all cycles studied. 58% (7 of 12) of the women showed a normal menstrual cycle (26 to 32 days). 33% (4 of 12) of the women experienced one or two episodes of amenorrhea (90-134 days), whereas 8.3% of women (1 of 12) experienced episodes of spotting, six times in a period of 24 months of Uniplant use (10-30 days). Before Uniplant insertion, plasma concentration of sex hormone binding globulin was 72.3 nmol/L. After 24 months of Uniplant use, the concentration was 78.0 nmol/L.