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

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 Ist 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% 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.