Levonorgestrel-releasing intrauterine system delivers prolonged effects

The long-acting contraceptive option, 52-mg levonorgestrel-releasing intrauterine system (52-mg LNG-IUS), appears to be highly effective, with high user satisfaction and a favourable safety profile, through 8 years of use, according to data from the Mirena Extension Trial.

The multicentre, single-arm study was conducted in the US and involved women aged 18–35 years who had been using 52-mg LNG-IUS for 4.5–5 years. Researchers evaluated contraceptive efficacy (Pearl Index), the cumulative failure rate (using the Kaplan–Meier method) of 52-mg LNG-IUS during extended use, bleeding outcomes, and adverse events.

Of the 362 participants who were still using 52-mg LNG-IUS at year 6, 243 entered the extension trial and 223 completed 8 years of 52-mg LNG-IUS use. Their mean age was 29.2 years, with everyone aged ≤36 years at the end of year 8. More than half of the participants were parous. There were two pregnancies recorded, with the device in situ in both cases.

The first pregnancy occurred at year 6 and had undetermined location and resolved spontaneously; while the second pregnancy occurred at year 7, was ectopic, and resolved with methotrexate treatment. In both cases, the 52-mg LNG-IUS was removed, and the participants withdrew from the trial.

Over years 6–8, the 3-year Pearl Index was 0.28 (95 percent confidence interval [CI], 0.03–1.00), with a 3-year cumulative failure rate of 0.68 percent (95 percent CI, 0.17–2.71). The respective Pearl Indexes for years 6, 7, and 8 were 0.34, 0.40, and 0.00. The 3-year (years 6–8) ectopic pregnancy Pearl Index was 0.14.

Treatment-emergent adverse events were documented in 249 out of 362 participants (68.8 percent), with 65 (18.0 percent) events deemed to be related to the 52-mg LNG-IUS. The rate of discontinuation was 38.4 percent, and the most common reason was wish for pregnancy (12.2 percent).

During extended use (years 5–8), the participants experienced reduced bleeding/spotting days, with approximately half of them reporting amenorrhea or infrequent bleeding. By year 8, 98.7 percent of the participants who completed the study expressed satisfaction with the continued use of 52-mg LNG-IUS.

Meanwhile, 24 out of the 31 women who discontinued early due to wish for pregnancy reported conceiving within 1 year of device removal, yielding a 12-month return-to-fertility rate of 77.4 percent.