Objective: To investigate the contraceptive efficacy, cycle control and acceptability of Implanon, a new single-rod, progestogen-only contraceptive implant.

Methods: In a non-comparative, open, multicenter study, a contraceptive implant containing the progestogen etonogestrel was inserted into 200 healthy women. The study duration was 2 years, with an optional extension up to 4 years.

Results: Women were exposed to Implanon for 644.6 woman-years. There were no pregnancies during the study. Per 90-day reference period, the median number of bleeding-spotting days ranged between 18 and 21 and the median number of bleeding-spotting episodes was two. The mean overall incidence of prolonged bleeding fell markedly during the study, from 69% in the first reference period to 26% in the 16th period. The most common adverse events were related to disturbed bleeding pattern and amenorrhea. Heavy or prolonged bleeding caused 18 subjects to withdraw from the study. Only a few subjects discontinued the study early due to irregular bleeding (2%) or amenorrhea (2%). A slight increase in mean body weight was observed. The implant was removed in an average time of 2.9 min.

Conclusions: Implanon demonstrated excellent contraceptive efficacy for 4 years of use and was well tolerated. The incidences of prolonged bleeding and amenorrhea both fell markedly with continued implant use. Because of its single-rod design, Implanon was quickly removed with few complications and proved to be a highly acceptable method of contraception.