A Cochrane review 1 [Abstract] included 9 trials with a total of 2 776 women. Different types of contraceptive implant were compared. There was no difference between Implanon (etonogestrel, 1 rod) and Norplant (levonorgestel, 6 capsules) for contraceptive effectiveness rates or continuation over 4 years (8 trials, n=1 578). No pregnancies occurred in any of the trials during 26 972 and 28 108 women months of follow up respectively. There was no difference in contraceptive effectiveness or continuation rates between Jadelle (levonorgestrel, 2 rods) and Norplant (1 trial, n=1 198). The most common side-effect with all was changes in bleeding pattern. After two years use the amenorrhoea rate was significantly higher with Implanon than Norplant. Implanon was quicker to insert and Implanon and Jadelle were quicker to remove compared to Norplant.
A prospective observational cohort study 2 (The Contraceptive CHOICE Project, n= 9 256) that provided no-cost contraception to women in the USA compared the rate of failure of different contraceptive methods in the overall cohort and in groups stratified according to age (less than 21 years of age vs. 21 years or older). Among the 7 486 participants 334 unintended pregnancies were identified. Women using contraceptive pills, transdermal patch, or vaginal ring had higher rates of unintended pregnancy than those using long-acting reversible contraception (LARC: IUDs, n=4 200; and implants, n=1 168). Failure rates for the pills, patch, or ring were 4.8%, 7.8%, and 9.4% in years 1, 2, and 3, respectively; the corresponding rates in the group using IUDs or implants were 0.3%, 0.6%, and 0.9% (P<0.001). The failure rates for depot medroxyprogesterone acetate injection were similar to those for IUDs or implants (0.1%, 0.7%, and 0.7% for years 1, 2, and 3, respectively; P=0.96). The contraceptive failure rate among participants using pills, patch, or ring was 4.55 per 100 participant-years, as compared with 0.27 among participants using LARC (hazard ratio after adjustment for age, educational level, and history with respect to unintended pregnancy, 21.8; 95% confidence interval, 13.7 to 34.9). Among participants who used pills, patch, or ring, those who were less than 21 years of age had a risk of unintended pregnancy that was almost twice as high as the risk among older participants.
A prospective cohort study 3 evaluated the effectiveness of the contraceptive implant and the 52-mg hormonal intrauterine device in women using the method for 2 years beyond the current approved 3 and 5 years of use, respectively. There have been no documented pregnancies in implant users during the 2 years of postexpiration follow-up (n=291 with 444 woman-years). Two pregnancies have been reported in levonorgestrel intrauterine device users (n=496 with 696.9 woman-years). The failure rate in the sixth year of use of the levonorgestrel intrauterine device is calculated as 0.25 (95% CI 0.04 to 1.42) per 100 woman-years; failure rate during the seventh year is 0.43 (95% CI 0.08 to 2.39) per 100 woman-years. Among implant users the median etonogestrel level was 207.7 pg/mL (range 63.8-802.6 pg/mL) at the time of method expiration, 166.1 pg/mL (range 67.9 25.0-470.5 pg/mL) at the end of the fourth year, and 153.0 pg/mL (range 72.1-538.8 pg/mL) at the end of the fifth year. Median etonogestrel levels were compared by body mass index at each time point and a statistical difference was noted at the end of 4 years of use with overweight women having the highest serum etonogestrel (195.9; range 25.0-450.5 pg/mL) when compared to normal (178.9; range 87.0-463.7 pg/mL) and obese (137.9; range 66.0-470.5 pg/mL) women (P = .04).
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