Tell me more about the contraceptive implant


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 from which to choose. There’s a good amount to know about the contraceptive implant — and the first item to address is that the version called Implanon is no longer available! Implanon’s manufacturer, Merck, has made a few improvements on this device with a newer version called Nexplanon. It’s virtually the same as the older version, but has a few additional benefits (more on that in a bit). Generally speaking though, this method is injected underneath the skin of the upper arm by a health care provider. The small, rod-shaped implant slowly releases a hormone called etonogestrel (a type of progestin) over the course of three years in order to provide long-lasting pregnancy prevention for the duration of use. The etonogestrel works in three ways: First, it prevents ovulation so that there isn’t an egg released to be fertilized. 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. This device is considered highly effective for most users, but may not be appropriate for everyone.

A few more specifics about this method: The plastic rod (for both the old and new versions of the device) is 40 millimeters (mm) in length and two mm in diameter (about the size of a matchstick). It’s inserted relatively painlessly (for many) into the underside of the upper arm after local anesthetic is used to numb the area and the procedure takes about one minute. The implant is designed so that the rod isn’t easily visible, but can be felt just underneath the skin. Some users may experience slight swelling or bruising after insertion, but it tends to go away within a short period of time. The rod contains 68 milligrams of etonogestrel that is released over a three-year period (though there is some evidence to indicate that the hormones from the device may remain at levels that would be enough to protect against pregnancy for up to the fifth year of use). The removal of the rod takes slightly longer than the insertion, but with the use of local anesthetic, pain from removal can be minimized. 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. A new one can be inserted immediately after the old one has been removed. If it isn't replaced or use is discontinued, users usually quickly return to fertility (i.e., have the ability to conceive).

The newer version, Nexplanon, differs in a few ways to the benefit of both the user and the provider. First, the updated device has an applicator that allows for one-handed insertion by the health care provider, increasing ease with and decreasing time needed for the insertion. The other improvement with the newer version is encountered when the device is ready to be removed. It can be located using an x-ray machine when necessary, making removal a bit easier even if not inserted properly.

The implant seems to be highly effective for many individuals. Due to the reduction of risk associated with user error (because it's inserted by a medical professional and no daily maintenance is required), the method is upwards of 99 percent effective at preventing pregnancy. If inserted within five days after the start of a user’s menstrual period, the method becomes effective immediately. Despite this high effectiveness rate, the method doesn't provide protection against sexually transmitted infections (STIs). So, it's wise to consider complementary methods of prevention, such as condoms. That said, the device can be used safely by those who are breastfeeding, which isn’t the case with all birth control methods. Like other forms of hormonal contraception, however, it’s key to know that there are some side effects associated with the use of the implant. Of note is the potential to experience irregular bleeding, changes in how long users have their periods (either shorter or longer than is typical for them), or not having a menstrual period at all. Other commonly reported side effects include weight gain, acne, headaches, breast tenderness, changes in mood, and abdominal pain. Mayo Clinic mentions that if a user develops breast lumps, heavy vaginal bleeding, symptoms of a blood clot, jaundice, infection, possible pregnancy, changes in blood pressure, migraine with aura, or significant depression, that it be brought up with a medical professional. Experiencing these issues may indicate that it would be best that the device be removed.

With that in mind, the implant may not be the contraceptive choice for everyone. The device isn’t recommended for folks who are or may be pregnant, have allergies associated with any part of the device, genital bleeding that hasn’t been diagnosed, certain cancers, have had a history of blood clots or stroke, or liver tumors or disease. There are also some medications and supplements that may decrease the implant’s effectiveness when used at the same time, such as St. John’s wort, some medications to treat seizures, certain sedatives, and some medications used to treat human immunodeficiency virus (HIV). Further, for those with a with a body mass index (BMI) above 30, there is some concern that the method may be less effective — though there is some evidence to suggest it may provide sufficient protection against pregnancy at any BMI. Because more evidence on this topic is needed and every individual is different, talking with a health care provider about whether or not the implant would be appropriate to use, given a potential user’s health history, is especially crucial.

For even more information about birth control options, check out the Go Ask Alice! Contraception category in the Sexual & Reproductive Health archives.

Last updated Feb 15, 2019
Originally published Feb 14, 2003

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