A 4-year pilot study on the efficacy and safety of Implanon, a single-rod hormonal contraceptive implant, in healthy women in Thailand.

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

Methods: In an open, non-comparative pilot study, 100 healthy women received a contraceptive implant containing the progestogen etonogestrel (3-ketodesogestrel) for 2 years with an optional extension up to 4 years.

Results: Subjects were exposed to Implanon for 296.1 woman-years. There were no pregnancies during the study. Per 90-day reference period, the median number of bleeding-spotting days was 10 and the median number of bleeding-spotting episodes was 2. Amenorrhea occurred in 24-39% of subject during the first 2 years and in about 20% in those who continued in the 3rd and 4th years. The most common drug-related adverse event was headache (7%). A slight increase in body mass index was observed. Only a few subjects discontinued treatment early, due to bleeding irregularities (6%) or amenorrhea (1%). The cumulative discontinuation rates were 13.4% after 2 years, 25.3% after 3 years and 28.0% after 4 years of use. Within 3 months of implant removal, six normal pregnancies occurred, indicating a rapid return of fertility. The average time taken for insertion of the implant was 0.5 min, compared with 2.5 min for removal.

Conclusions: Implanon demonstrated excellent contraceptive efficacy and was well tolerated during up to 4 years of use. The vaginal bleeding pattern was variable and was characterized by relatively few bleeding events, but proved acceptable to most subjects. Because of its single-rod design, Implanon was quickly inserted and removed without complications.