Implanon and Nexplanon: The contraceptive implant

Originally Published: February 14, 2003 - Last Updated / Reviewed On: May 1, 2015
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Alice,

Can you tell me all you know about the contraceptive called Implanon and its effects on the body?

Dear Reader,

Kudos to you for seeking out more information about birth control methods; there are a great many options to choose from! To answer your question: Implanon is contraceptive implant that's injected underneath the skin of the upper arm by a health care provider. The small, rod-shaped implant slowly releases a progestogenic hormone called etonogestrel over the course of three years in order to provide long-lasting prevent pregnancy during that time. The etonogestrel works in three ways. First, it tricks the body into thinking it's pregnant, which prevents the ovaries from releasing eggs. It also thickens cervical mucus, making it difficult for sperm to enter the uterus. Lastly, it changes the lining of the uterus, preventing any egg that does happen to get fertilized from implanting itself in the uterine wall. What you may not have known is that Implanon’s manufacturer, Merck, has made a few improvements on this method with a newer version called Nexplanon. It’s virtually the same as Implanon, but has a few additional benefits (more on that in a bit). Both versions of the contraceptive implant are highly effective for most users, but may not be appropriate for everyone.

The rod (for both Implanon and Nexplanon) is 40 millimeters (mm) in length and two mm in diameter (about the size of a matchstick), and is made of a biodegradable synthetic (commonly used in artificial joints). Implanon and Nexplanon are similar in that each one is inserted relatively painlessly into the underside of the upper arm after local anesthetic is used to numb the area — the procedure takes about one minute. The one benefit that Nexplanon has that Implanon does not is that the former has an applicator that allows for one-handed insertion by the health care provider, increasing ease and decreasing time needed for the insertion. With either type, the devices are designed so that the rod isn’t easily visible (unless a user is very thin), but can be felt just underneath the skin. Tissue forms around the rod after insertion to make sure that it doesn't move. Some users may experience slight swelling after insertion, but other issues are rare. The rod contains 68 milligrams of etonogestrel that is released over a three-year period. About 60 to 70 micrograms (µg) per day are released in the first year and the amount decreases over time until only about 25 to 0 µg per day are released in the third year. After the third year, the implant will continue to release some hormone, but it will be at levels too low to prevent pregnancy.

The removal of the rod takes slightly longer than the insertion — about two minutes — but with the use of local anesthetic, it's also relatively painless. A health care provider will make a very small incision in the skin near the tip of the rod and then pull the rod out from underneath the skin. Within several days of removal, etonogestrel will no longer be in the blood stream, and fertility should return to normal within one month. There's a possibility that there will be a small scar (2 mm) where the rod was removed. When inserted properly, a health care provider may use just her/his fingers to feel for the device in order to remove the Implanon implant. When inserted improperly, an ultrasound or other more advanced technique may be necessary to locate it. Nexplanon, on the other hand, can be located using an x-ray machine when necessary, increasing the ease of removal even if not inserted properly (another perk!).

Implanon seems to be highly effective for many individuals. In studies of over 2000 women for three years, not one became pregnant. The makers of Implanon do warn, however, that no method of contraception can be 100 percent effective. Nexplanon has been shown to have comparable efficacy. However, like other forms of hormonal contraception, these methods do have some side effects. A small percentage of women have reported irregular (or missed) periods, weight gain, acne, headaches, breast tenderness, hair loss, changes in mood and/or libido, abdominal pain, painful periods, or an increase in blood pressure. Managing side effects is yet another important to have regular follow-up appointments with your health care provider. Most health care providers see users for six-month checkups while using the implant. During clinical trials (of Implanon), about 30 percent of the women in Europe and Canada discontinued use within two years, primarily due to complaints about irregular bleeding.

The contraceptive implant isn’t for everyone. It is possible that Implanon and Nexplanon are not as effective in individuals who are overweight or obese. Because the amount of hormones released through the implanted rod is the same across the board, individuals who are overweight or obese may not receive enough relative to body size to prevent pregnancy. However, obese women have not yet been included in Implanon and Nexplanon studies. Because more evidence on this topic is needed, talking with a health care provider about whether or not Implanon or Nexplanon would be appropriate to use, given a potential user’s health history, is especially crucial. Additionally, individuals who have a hormone-dependent cancer, active thrombosis, or severe liver disease are advised to consider contraceptive options other than Implanon or Nexplanon. For even more information about birth control options, check out the Go Ask Alice! Contraception category in the Sexual & Reproductive Health archive.

Alice

For more information or to make an appointment, check out these recommended resources:

Medical Services (Morningside)

Student Health Service (CUMC)