Clinical Performance and Levonorgestrel Levels of Sinoplant and Indoplant after Five Years of Continuous Use

Abstract

Objectives: To compared serum LNG concentrations, contraceptive effectiveness, safety, and acceptability between Sinoplant and Indoplant over five years of continuous use to explore their potential for extended use.

Methods: This prospective cohort study was a two-year extension of a three-year multicenter randomized clinical trial conducted at family planning clinics in Yogyakarta and Surabaya, Indonesia. Of the initial 540 participants, 58 voluntarily consented to participate in the extension study. Serum LNG concentrations were measured at 36, 48, and 60 months. Nonparametric tests were used because of the skewed distribution of the data.

Results: Fifty-five participants completed the 60-month follow-up. At month 60, all participants (100%) had negative urine pregnancy test results. Median serum LNG concentrations at months 36, 48, and 60 were 361.95, 555.00, and 400.00 pg/mL, respectively, in the Sinoplant group and 254.52, 210.00, and 230.00 pg/mL, respectively, in the Indoplant group. Significant within-group variation over time was observed only in the Sinoplant group (p = 0.006). No significant between-group differences were observed in overall adverse events or acceptability.

Conclusion: Both implants maintained median serum LNG concentrations above the minimum contraceptive threshold of 180 pg/mL and demonstrated preliminary evidence of continued contraceptive effectiveness through five years of continuous use. However, the small sample size of the extension study and potential selection bias limit the generalizability of these findings. Larger prospective studies are needed before changes to policies regarding extended implant use can be recommended.

Keywords: five years of continuous use; Indoplant; levonorgestrel; Sinoplant; two-rod implant.