Long-Acting Hormonal Methods

Implanon Contraceptive Implant

Average Failure Rate: less than 1%

Implanon is a type of long-term birth control that is inserted under the skin by a doctor. It is a flexible plastic rod, the size of a matchstick, that is surgically placed under the skin of a woman's arm. Implanon contains a synthetic progestin hormone called etonogestrel. Implanon is effective for up to three years.

Implanon is more effective than many other methods of birth control because it eliminates user-error, such as forgetting to take a pill or inserting a barrier method improperly. After insertion it takes seven days for Implanon to become effective. It is not known if Implanon is as effective in women who are more than 30% over their ideal weight because studies did not include many overweight women. However, Norplant, an earlier version of Implanon, was less effective in heavier women. Implanon must be surgically removed after the 3 year period.

How Implanon Works as Birth Control

Like other progestin-only hormonal contraceptives, Implanon prevents pregnancy in several ways. The primary way is by stopping release of an egg from the ovaries. Implanon also changes the mucus in the cervix and this may keep sperm from reaching the egg. Implanon also has post-fertilization mechanisms, whereby the hormone changes the lining of the uterus, making it harder for a fertilized egg to implant and develop. More about how this works...

Side Effects and Health Risks of Implanon

The most common side effect of Implanon is a change in menstrual cycles. Users can expect their menstrual period to be irregular and unpredictable throughout the time Implanon is in place. This may mean more bleeding, less bleeding, or no bleeding at all. Other common side effects that caused women to stop using Implanon in clinical studies were mood swings, weight gain, headache, acne, and clinical depression.

Because Implanon is surgically placed under the skin, it may cause a small scar. If Implant is not placed properly, it may not prevent pregnancy, or it may be difficult or impossible to remove. (This can be especially problematic if the user has an allergic reaction to the implant.) There have been reports of Implanon getting "lost" or breaking inside of a woman, especially during the removal procedure. Removals of deeply inserted implants can lead to serious scarring, nerve damage, or other complications. If the implant cannot be removed, this may result in infertility, pregnancy outside of the womb (ectopic pregnancy), or inability to stop a drug-related allergy.

Implanon does not offer any protection from STDs, and in fact all hormonal methods appear to increase the risk of acquiring HIV and other STDs from an infected partner.

Documented Side Effects of Implanon
Side Effect Approximate Users Affected
Too Much / Very Heavy Menstrual Bleeding 1 in 4
Infrequent Menstruation 1 in 4
No Periods 1 in 5
Headaches 1 in 6
Yeast Infection 1 in 7
Weight Gain 1 in 7
Acne 1 in 7
Breast Pain 1 in 8
Upper Respiratory Tract Infection 1 in 8
Abdominal Pain 1 in 9
Sore Throat (Pharyngitis) 1 in 10
Vaginal Discharge (Leukorrhea) 1 in 10
Flu-Like Symptoms 1 in 13
Increased Cramps / Painful Menstruation (Dysmenorrhea) 1 in 14
Dizziness 1 in 14
Back Pain 1 in 15
Mood Swings 1 in 15
Nausea 1 in 16
Pain 1 in 18
Nervousness/Anxiety 1 in 18
Sinus Infection 1 in 18
Clinical Depression 1 in 18
Pain at Insertion Site 1 in 19

Information listed includes only those symptoms reported by users. Actual numbers may be higher.

Source: Implanon Prescribing Insert for Health Care Providers.

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