The widely-prescribed contraceptive implant Nexplanon has recently been linked to an increased risk for serious blood clots. This alternative method of birth control is implanted into the arm, and gradually releases a low dose of the progestin etonogestrel over a three year period. Nexplanon manipulates key female hormones, and in doing so, increases the likelihood the user will develop a potentially life-threatening type of blood clot known as deep vein thrombosis (DVT).
How Does Nexplanon Work?
Manufactured and marketed by Merck & Co., Nexplanon is a small plastic implant designed to be inserted under the skin of the upper arm to prevent pregnancy for up to 36 months. The implant is approximately 4cm long and 2mm in diameter. Nexplanon contains a synthetic hormone known as etonogestrel, which is continuously released into the bloodstream to prevent pregnancy in two ways.
In a woman’s normal menstrual cycle, an egg matures and is released from the ovaries each month in a process known as ovulation. The ovary then produces a hormone called progesterone which prevents the release of additional eggs and readies the lining of the womb for a possible pregnancy. If the woman does become pregnant, progesterone levels in her body remain elevated, maintaining the womb lining. If pregnancy does not occur, progesterone levels fall and the menstrual period begins.
The etonogestrel contained in Nexplanon tricks the body into thinking that ovulation has already occurred by maintaining high levels of the synthetic progesterone. This prevents the release of eggs from the ovaries, and is the main way in which Nexplanon reduces the likelihood of an unwanted pregnancy. Etonogestrel also increases the thickness of natural mucus in the cervix, creating a condition that makes it more difficult for sperm to cross from the vagina into the womb. By preventing sperm from entering the womb, successful fertilization of an egg is far less likely to occur.
Nexplanon Blood Clots
Since it was first approved by the U.S. Food & Drug Administration (FDA) in November 2011, Nexplanon has been increasingly linked to potentially life-threatening blood clots. These clumps occur when blood hardens from a liquid to a solid. A blood clot that forms inside a blood vessel and stays in place is referred to as a thrombus. A thrombus that breaks free and migrates from one location to another is called an embolus. When an embolus travels through the circulatory system and ends up clogged in the lungs it is called a pulmonary embolism.
Signs & Symptoms
Deep vein thrombosis (DVT), the type of blood clot most often associated with Nexplanon, usually occurs deep in the leg veins. DVTs in the leg cause swelling, pain, increased warmth, and redness at the site of the clot. The classic symptoms of deep vein thrombosis include:
- tenderness or pain over a vein
- sharp, shooting pain when the foot is being flexed
- warm sensation
- dull, aching throb in the calves, especially when the person is walking
- widening or dilation of the surface veins
Treatment & Prognosis (Outlook)
Treatment for Nexplanon-induced deep vein thrombosis usually involves anticoagulation, which is intended to inhibit further growth of the blood clot and prevent it from developing into an embolus that can travel to the lungs. Anticoagulation is usually accomplished through treatment with Coumadin (generic: warfarin) and Lovenox (generic: enoxaparin), two drugs that work by different mechanisms to thin the blood. In rare cases where these anticoagulants are ineffective, surgical intervention may be the next option. Surgery typically involves placing an IVC (inferior vena cava) filter to prevent future clots from migrating to the lungs.
Even though the prognosis for recovery from deep vein thrombosis is generally quite favorable, there is a significant risk of chronic venous insufficiency (also known as post-thrombotic syndrome). In this situation, patients may experience persistent swelling and tenderness of the affected leg and an increased risk of recurrent ulceration. After an asymptomatic DVT, the risk of these complications is only about 5%. Two years after a symptomatic above-the-calf (proximal) DVT has been treated, the incidence of complications is 25 to 50%. Seven to 10 years after treatment, the incidence is as high as 70 to 90%. The recurrence rate of DVT in untreated patients is 50% within the first three months.