Mirena® (levonorgestrel-releasing intrauterine system) 52 mg

Who is not appropriate for Mirena

Use of Mirena is contraindicated in women with: known or suspected pregnancy and cannot be used for post-coital contraception; congenital or acquired uterine anomaly, including fibroids if they distort... Continue below

Mechanism of Action (MOA)

Locally Acting


The local mechanism by which continuously released levonorgestrel (LNG) enhances the contraceptive effectiveness of Mirena® has not been conclusively demonstrated.

Studies suggest that the continuous release of LNG begins a cascade of effects that work together locally to achieve contraceptive effectiveness:


Thickening of cervical mucus
Inhibition of sperm capacitation or survival
Alteration of the enometrium
  • Initially, LNG is released at a rate of approximately 20 mcg/day. This rate decreases progressively to approximately 10 mcg/day after 5 years and 9 mcg/day after 6 years.

  • A stable serum concentration, without peaks and troughs, of LNG of 150-200 pg/mL occurs after the first few weeks following insertion of Mirena. LNG concentrations after long-term use of 12, 24, 60 and 72 months were 180±66 pg/mL, 192±140 pg/mL, 159±59 pg/mL, and 121±49 pg/mL, respectively.

  • Low doses of LNG are administered into the uterine cavity

In the event of pregnancy
  • If pregnancy should occur with Mirena in place, remove Mirena because leaving it in place may increase the risk of spontaneous abortion and preterm labor. Removal or manipulation may result in pregnancy loss. Evaluate women for ectopic pregnancy because the likelihood of a pregnancy being ectopic is increased with Mirena. Tell women about the signs of ectopic pregnancy and associated risks, including loss of fertility. Women with a history of ectopic pregnancy, tubal surgery, or pelvic infection carry a higher risk of ectopic pregnancy