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Implanon is a subdermal implant developed for the purpose of contraception. It was approved by the Food and Drug Agency (FDA) in 2006, and since then, it has been widely used. The active substance contained in Implanon is etonogestrel, a synthetic analogue of the natural female sex hormone progesterone. It is usually inserted beneath the skin, six to eight centimeters above the elbow of the non-dominant arm.

Efficacy and safety issues of Implanon have been extensively studied during the past decade.

Mechanism Of Action

Each implant is 4 cm long and contains a solid core with 68 mg of etonogestrel. As the active substance is released gradually, the implant can be effective in preventing pregnancy for more than three years. Cyclic changes in sex hormone levels during menstrual cycle are necessary for maturation of follicles in ovaries, ovulation, and preparation of uterine mucosa for conception.

Etonogestrel induces changes in hormonal balance of several hormones, thus preventing ovulation and making mucosa of the uterus unsuitable for conception.

Efficacy Of Implanon

In a study conducted in 2009, which compared results of 11 studies assessing efficacy of Implanon and included nearly 1000 patients, no pregnancies were reported. Based on these results and the results of many other randomized clinical trials, Implanon has proven to be as efficient as other commonly used types of contraception, including sterilization. However, a mutual limitation of these studies was that they did not include obese women, even though there are scientific grounds to believe that Implanon could be less efficient in women with a higher percentage of fat tissue. This is due to etonogestrel being highly dissolvable in fat. A significant number of pregnancies were detected in Australia during post marketing surveillance, but the investigation showed possible flaws in the process of implant insertion.

The efficacy of Implanon highly depends on proper insertion and the absence of complications, so regular checks by your health care provider are necessary.

Side Effects And Safety Issues

Implanon is well tolerated, although it can produce side effects as a consequence of changed hormonal balance.

The most common complaint of women using Implanon was irregular bleeding. It is important to mention that slight changes in amount and frequency of bleeding are expected with any hormone-based contraceptive method. According to the results of recent studies, infrequent bleeding was present in almost 30 percent of women using Implanon, prolonged bleeding in 15 percent, while only 11 percent of women had normal bleeding patterns. Your gynecologist should assess the severity of your bleeding abnormality and whether it is an indication for implant removal.

Bleeding abnormalities are the most common reason for premature removal of Implanon.

Other side effects include dermatological, psychiatric, and weight disturbances. New onset or worsening of the existing acne was reported in 10 to 15 percent of women using Implanon. Similar percentage of women also reported different levels of weight gain. Some patients experienced episodes of psychiatric disorders, such as depression, emotional lability, and anxiety.

Some drugs can interact with etonogestrel, thus lowering its efficacy, especially those which are metabolized in liver.

Always consult your doctor about all the medications you use in order to prevent unwanted drug interactions.

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