<prompt> Mirena releases ___ of LNG per day.20 mg20 microgram52 mg52 microgram  <response>: Mirena contains a total of 52 mg levonorgestrel LNG. LNG is released into the uterine cavity at a rate of approximately 20 microgramday. The LNG IUD is about as effective as sterilization, but, unlike sterilization, it is easily reversible. These devices act mainly by local progestogenic effects and act for up to 5 years. 