Mirena Facts

Mirena is an intrauterine device (IUD), which a doctor or nurse practitioner inserts to prevent pregnancy. This IUD is a small, soft plastic t-shaped device containing the hormone Levonorgestrel, a form of progesterone. The contraceptive is effective for up to five years, after which it must be removed, but it can be replaced at that time. Unlike oral contraceptives, Mirena does not contain estrogen.

Function

• Mirena primarily works by altering the texture of cervical mucus and the uterine lining. This makes it difficult for sperm to reach an egg. In the event an egg does become fertilized, the effects of Mirena prevent the egg from implanting in the uterus. In some women, Mirena prevents ovulation. The effectiveness rate is 99.9 percent, according to the Mayo Clinic, so one woman out of 1,000 using the device for one year will get pregnant.

Considerations

• Because 20 percent of women who discontinue using Mirena in order to get pregnant have trouble conceiving over the next year or longer, the manufacturer recommends women only use this IUD if they already have children or do not want children. Menstruation can be irregular for up to the first six months after the IUD has been inserted. The woman must check after each period for the threads that are connected to the IUD. If she cannot locate the threads, the IUD may have fallen out or have become displaced, and she should contact the doctor.

Side Effects

• Any IUD can cause side effects, and additional effects also are possible with Mirena because the device contains progesterone. Many women do not experience negative side effects, but some possibilities include acne and other skin problems, breast tenderness or pain, changes in sex drive, hair loss, low back pain, nausea, abdominal pain and weight gain. Most women experience lighter periods and a decrease in menstrual cramps. Rarely, Mirena can result in liver problems, blood clots or pelvic inflammation.

Contraindications

• Women may not be able to use Mirena if they have any abnormal conditions of the uterus or have had any disorders or infections in the pelvic area. These disorders include uterine fibroids, pelvic inflammatory disease, ectopic pregnancy, endometriosis, recent infected abortion, unexplained vaginal bleeding, vaginal or cervical inflammation, or a sexually transmitted disease. Additionally, any cancers which could be worsened by hormone use may be a contraindication for Mirena, including breast, cervical, ovarian or uterine cancer.

Drug Interactions

• Many drugs interact with Levonorgestrel, and a woman taking these medications may not be able to use Mirena. These include certain antibiotics and antifungal medications, anticoagulants, barbiturates, beta-adrenergic blockers, carbamazepine, corticosteroids, insulin, medications to treat human immunodeficiency virus (HIV), modafinil and selegiline. These drugs can increase or decrease the effectiveness of Levonorgestrel.