New contraception: Implanon?

Originally Published: February 14, 2003 - Last Updated / Reviewed On: April 20, 2007
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Can you tell me all you know about the contraceptive called Implanon and its effects on the body?

Dear Reader,

Implanon is a relatively new contraceptive technology that's injected underneath the skin of the upper arm by a health care provider. It was approved by the U.S. Food and Drug Administration in 2006. It's much like Norplant (which is no longer available in the United States), but with only one rod. The Implanon rod slowly releases a progestogenic hormone called etonogestrel over the course of three years.

Implanon 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. A woman won't be able to see the rod (unless she is very thin), but she can feel it with her fingers. Tissue forms around the rod after insertion to make sure that it doesn't move. Some women may experience slight swelling after insertion, but other problems are rare.

The rod itself is 40 mm in length and 2 mm in diameter (about the size of a match stick), and is made of a biodegradable synthetic material that is commonly used in artificial joints. Implanon can be inserted at any time, but health care providers recommend having it inserted between the first and fifth day of menses or, if a woman is on the pill, the day after she takes the last pill for the month. If Implanon is inserted at any other time, it's recommended that a woman use other contraception for the next seven days.

The Implanon rod contains 68 milligrams of etonogestrel that is released over a three-year period. About 60 - 70 micrograms (µg) per day are released in the first year and the amount decreases over time until only about 25 - 0 µg per day are released in the third year. After the third year, Implanon will continue to release some hormone, but it will be at levels too low to prevent pregnancy.

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.

While using Implanon, most health care providers see users for 6-month checkups. During clinical trials, about 30 percent of the women in Europe and Canada discontinued use within 2 years, primarily due to complaints about irregular bleeding. This number is not significantly different from discontinuation rates for Norplant.

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.

Implanon seems to be highly effective. 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.

Like other forms of hormonal contraception, Implanon does have some side effects. According to a review of Implanon published in The Annals of Pharmacotherapy in 2001, about 47 percent of women reported at least one side effect during the three years. Irregular (or missed) periods, weight gain, acne, headaches, or breast tenderness each occurred in about 5 percent of Implanon users. Another 2.5 percent of users experienced hair loss, changes in mood and/or libido, abdominal pain, or painful periods. Another known side effect is an increase in blood pressure, which is why it's important to have regular follow-up appointments with your health care provider.

Women who have a hormone-dependent cancer, active thrombosis, or severe liver disease need to consider contraceptive options other than Implanon.