An estimated 2 million American women have a Mirena, a T-shaped intrauterine device (IUD) that contains the hormone levonorgestrel, a type of progestin, which is released over time.
The device can remain in the body providing birth control for up to five years. Like other IUDs, Mirena claims to be over 99 percent effective at preventing pregnancy. Levonorgestrel is also taken orally in emergency contraception to prevent pregnancy after unprotected sexual intercourse.
The first levonorgestrel IUD, Mirena, was first introduced by Schering AG in Finland in 1993 and later made available in dozens of other countries. The FDA approved it for the U.S. market in December 2000. Schering was purchased by Bayer in 2006. The device is now available in more than 100 countries.
Bayer also markets two other intrauterine devices that it says are part of the Mirena family – Kyleena and Skyla. According to the company’s 2016 annual report, the product line was one of its top sellers, bringing in almost $1.2 billion worldwide, including nearly $800 million in the United States. That compares to about $1.1 billion worldwide with about $727 million in the U.S. in 2015. The company says its patent on the method of insertion for Mirena doesn’t expire until 2029.
Mirena is considered as effective as sterilization in preventing pregnancy.
A Canadian researcher described Mirena as the “gold standard” among levonorgestrel-releasing IUDs. It has been the subject of more than 2,000 published studies that examined its uses in gynecology and family planning.
News reports said sales of IUDs and other long-term forms of birth control received a boost in the U.S. after the November 2016 elections, as women worried their healthcare coverage would diminish rushed to get contraception that would outlast the presidency.
How Does Mirena Work?
IUDs with levonorgestrel work mainly by making it difficult for sperm to fertilize an egg. Mirena slowly releases 20 mcg of the synthetic hormone into the uterus each day. Birth control pills, in comparison, typically release 150 mcg into the body daily.
Mirena prevents pregnancy in three ways: it slowly releases levonorgestrel which inhibts sperm’s ability to move, causes mucus in the cervix to thicken and thins the lining of the uterus.
Levonorgestrel has a long history of use in many approved hormonal products in the US. These uses include both contraception and menopausal therapy.
In some women, the hormonal secretion of the IUD is enough to prevent ovulation.
As a result, the fluid in the uterus changes to contain a high amount of white blood cells and other cellular changes that inhibit sperm’s ability to move in the uterus.
Another effect is that Mirena thickens the mucus in the cervix, blocking sperm from passing into the uterus or fallopian tubes where fertilization can happen. The thickened mucus may carry additional benefits, such as fewer upper genital tract infections and less pelvic inflammatory disease.
And finally, the Mirena changes the lining of the uterus, thinning it within three months of insertion. In addition to contraception, this can also have the effect of reducing or stopping menstrual bleeding while the Mirena is in place.
Mirena and other IUDs do not protect against sexually transmitted diseases.
Who Should Get a Mirena?
Mirena, which is recommended for women who have already had at least one child, was also approved by the FDA in 2009 to treat heavy periods in women who chose IUDs as their method of contraception. Some experts say that the device need not be limited to women who have given birth, as this restriction is not based on evidence.
Mirena is also usually recommended as contraception for patients with certain medical conditions, such as a history of deep venous thrombosis, type 1 diabetes, liver disease, epileptic seizures, and conditions involving a compromised immune system, such as HIV.
The flexible, plastic device is inserted vaginally by a trained healthcare provider during an office visit. It is made from medical grade polyethylene and has a cylindrical steroid reservoir made of silicone and 51 mg of levonorgestrel covering the vertical part of the T. It releases 20 mcg of levonorgestrel a day for five years.
The device costs about $800 and is covered under the contraception provision of the Affordable Care Act, meaning it should be provided at no charge to most women with insurance as long as the contraception mandate remains in place and the woman’s employer isn’t covered by one of the court-sanctioned religious exceptions.
Women Who Shouldn’t Use Mirena
Mirena is not recommended for women who:
- Have or get pelvic infections
- Are or may be pregnant
- Have or have had known or suspected breast cancer or other progestin-sensitive cancer
- Have uterine anomaly, including fibroids, if they distort the uterine cavity
- Have lower, uncontrolled genital tract infections
- Have unexplained uterine bleeding
- Have or have had a history of acute pelvic inflammatory disease
Caution is recommended for women who:
- Are taking anticoagulants or have coagulopathy
- Have migraine, focal migraine with asymmetrical vision loss or other symptoms of transient cerebral ischemia
- Experience exceptionally severe headaches
- Have anomalies or cancers of the reproductive system
- Have a marked increase of blood pressure or severe arterial disease, such as a stroke or heart attack
- Have liver disease
Insertion of Mirena
Mirena can be inserted by a doctor during a regular office visit. The procedure can be painful, with some women feeling pain similar to mild cramps, and others experiencing more severe pain. Many women, however, experience little or no pain. The procedure typically takes about five minutes and involves a speculum, an instrument to manipulate the uterus and another instrument to measure it so the Mirena is placed properly in the uterus.
The two horizontal arms of the T are folded upward during insertion so the device is shaped like a matchstick. At the conclusion of the insertion, the arms extend to the side. When in place, the Mirena is 32 mm tall and 32 mm across the top of the T.
The device has two threads attached to it, which are used to make sure Mirena is in place and to assist in its removal. Women are instructed to check their threads monthly. If the threads are not in place or have significantly shortened, they may have broken or retracted into the cervical canal or uterus.
Makers of Mirena recommend that patients see a doctor four to six weeks after having a Mirena inserted. The device becomes effective seven days after insertion.
Although use of IUDs was once thought to increase the risk of pelvic inflammatory disease, Mirena may actually help protect against infection, especially in women who have not previously given birth.
Side Effects and Complications
Some women report extreme pain during insertion and for several days after, while others experience relatively minor discomfort or cramping. The most common side effect of Mirena is changes in menstrual bleeding.
If pregnancy occurs in a patient who has Mirena, there is a danger of spontaneous abortion, preterm labor and ectopic pregnancy, which can be fatal.
Another risk associated with Mirena is that the device could perforate the wall of the uterus and travel to other parts of the body, potentially damaging other organs and tissue. Sometimes the Mirena spontaneously comes out of the body through the vagina. This happens most often in the first three months after placement and is rare later than that.
The Mirena can also have an effect on mood and some women experience dizziness. If the woman becomes pregnant, she must have her doctor remove the Mirena because of the danger of spontaneous abortion and preterm labor. However, removing it or manipulating it may result in the loss of the pregnancy.
The device can be removed at any time a patient would like to become pregnant. Bayer says 8 out of 10 women who have Mirena removed succeed in becoming pregnant within a year.
Some women report developing a condition called intracranial hypertension or pseudotumor cerebri, which is an unexplained increase of pressure inside the head, which can seem like the symptoms of a brain tumor and can lead to vision loss.
Regulatory and Legal Issues with Mirena
The FDA warned Bayer in 2009 that it was in violation of the federal Food, Drug and Cosmetics Act because advertising for Mirena contained false or misleading statements, suggesting using the device would lead to “increased levels of intimacy, romance and by implication, emotional satisfaction.” The FDA said there is no evidence to support that. The FDA also castigated Bayer for suggesting that women who use Mirena will “look and feel great” even though the device is sometimes linked to weight gain, breast and back pain, as well as acne.
According to the Bayer 2016 annual report, the company was facing lawsuits from approximately 2,600 users of Mirena as of the end of January 2017. The lawsuits allege that Mirena is defective and that women were harmed by the device. The plaintiffs claim they suffered injuries including perforation of the uterus, ectopic pregnancy and idiopathic intracranial hypertension, also known as pseudotumor cerebri. The company is expecting more lawsuits to be filed.
Most of the pending U.S. federal cases have been consolidated in a multidistrict litigation proceeding for common pre-trial management in New York. These do not include approximately 1,230 cases that were dismissed in July 2016 by a judge who excluded the plaintiffs’ expert witnesses, whom the judge said were not qualified to testify that Mirena could cause secondary perforation. Many of the cases pending in state court are consolidated in multicounty litigation in New Jersey.
As of January 23, 2017, five Canadian lawsuits relating to Mirena seeking class action certification had been served upon Bayer.
Bayer says it intends to defend itself vigorously.
Elaine Silvestrini is a career journalist with a strong desire to learn, explain, and help people. While working at Drugwatch, Elaine has reported on breaking news involving prescription drugs and medical devices and has written pieces on several large pharmaceutical companies and other topics. She is dedicated to telling people what they need to know about developments in the news, and helping consumers understand what they can do when something goes wrong with their drugs and medical devices.