The Food and Drug Administration (FDA) has expanded the approval of Mirena (levonorgestrel-releasing intrauterine system) for up to 7 years of pregnancy prevention. Previously, the intrauterine device was indicated for contraception for up to 6 years.
Mirena contains 52mg of levonorgestrel, which initially releases at a rate of approximately 20mcg/day. This rate decreases progressively to approximately 10mcg/day after 5 years and 8mcg/day after 7 years. By the end of the 7th year, Mirena should be removed and replaced at the time of removal with a new system if continued use is desired.
The approval was based on data from the phase 3 Mirena Extension Trial (ClinicalTrials.gov Identifier: NCT02985541) that evaluated the efficacy of Mirena during extended use beyond 5 years. The study included 362 women aged 18 to 35 years who had been using Mirena for not less than 4.5 years and no more than 5 years at enrollment. The primary endpoint was the pregnancy rate calculated as the Pearl Index (PI) at the end of year 6 and 7.
Results showed that the PI for the 7th year of use was 0.45 with a 95% upper confidence limit of 2.49 based on the 1 pregnancy that occurred during year 7 and within 7 days after Mirena removal or expulsion. The PI for the 6th year of use was 0.35 with a 95% upper confidence limit of 1.95 based on the 1 pregnancy that occurred during year 6 and within 7 days after Mirena removal or expulsion. The cumulative 2-year pregnancy rate for years 6 and 7 was 0.71 with a 95% upper confidence limit of 2.84 based on 2 pregnancies and 7269 exposure cycles.
Mirena is also indicated for the treatment of heavy menstrual bleeding for up to 5 years in women who choose to use intrauterine contraception as their method of contraception. For this indication, it should be replaced after the end of the fifth year if continued treatment of heavy menstrual bleeding is needed.
Mirena [package insert]. Whippany, NJ: Bayer HealthCare Pharmaceuticals Inc.; 2021.