Merck’s popular hormonal contraceptive Implanon (etonogestrel) has recently been linked to life-threatening blood clots and other serious side effects. A growing body of evidence seems to suggest that the progestin released by Implanon may increase a woman’s risk of developing deep vein thrombosis (DVT), a potentially life-threatening type of blood clot that usually forms in the legs. Signs and symptoms of an Implanon-induced DVT may include swelling, warmth, redness, and pain at the site of the clot.
How Does Implanon Work?
Implanon is a small, matchstick-shaped flexible plastic implant designed to be inserted under the skin of the upper arm. Like a number of other types of birth control, Implanon releases a hormone known as progestin. Hormones are chemicals made in our bodies that control a variety of different functions. The progestin contained in Implanon works by keeping a woman’s body from releasing eggs (ovulation). When there is no egg to join with the sperm, pregnancy cannot happen. Progestin also prevents pregnancy by thickening a woman’s cervical mucus, which blocks sperm and keeps it from joining an egg.
Implanon Blood Clots
Despite its relative effectiveness at preventing pregnancy, Implanon has been increasingly linked to a potentially life-threatening type of blood clot known as deep vein thrombosis (DVT). This condition occurs when a blood clot that forms in a vessel (usually the legs) dislodges itself and migrates through the bloodstream. If the clot becomes stuck in the lungs, it can block vital blood flow and result in a pulmonary embolism (PE).
Signs and symptoms of an Implanon-induced deep vein thrombosis may include:
- swelling in one or both legs
- pain or tenderness in one or both legs which may occur only while walking or standing
- warmth in the skin
- red or discolored skin
- visible surface veins
- leg fatigue
If you are using Implanon and are experiencing any of these symptoms, you should contact your healthcare provider immediately. Depending on your particular case, the doctor may recommend an MRI, ultrasound, blood test or venography to make a conclusive diagnosis.
DVT Risk Factors
While all forms of birth control have risks, it is often possible to reduce risk factors by taking certain steps. Before undergoing treatment with Implanon, discuss your individual level of risk for deep vein thrombosis with your doctor. You may be at an increased risk if you:
- are a smoker
- are overweight
- travel frequently, particularly in cramped situations (like flying)
- have a personal or family history of blood clots, heart disease, heart defects, or stroke
- have high blood pressure over 160/100 mmHG
- suffer from severe migraines
Side Effects of Implanon
In addition to being linked to blood clots, Implanon may also have the potential to cause the following side effects:
- pseudotumor cerebri (PTC)
- idiopathic intracranial hypertension (IIH)
- irregular bleeding
- change in sex drive
- discoloring or scarring of the skin over the implant
- infection or pain in the arm
- pain at the insertion site
- sore breasts
- weight gain