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.