News Review From Harvard Medical School -- Drug May Allow Long-Term Clot Prevention
A new drug may help to prevent blood clots in the legs without causing a risk of bleeding, new research suggests. Venous thromboembolism (VTE) is a blood clot that forms in a vein. If it travels to the lungs, heart or brain, it can be deadly. After hospital treatment, people with VTE take warfarin (Coumadin) for 6 to 12 months to help keep new clots away. The risk of new clots continues after this time. But people don't take warfarin longer because of a risk of bleeding. The new study included nearly 2,500 people who had completed standard treatment with warfarin after VTE. They were randomly assigned to receive apixaban or placebo (fake pills) twice a day. Apixaban reduces the risk of clots in a different way than warfarin. During the next year, 9% of those taking the placebo and 1.7% of those taking apixaban had a new VTE. People taking the drug also had much lower rates of death from heart or blood vessel problems. There was no increase of major bleeding. The New England Journal of Medicine published the study online. HealthDay News wrote about it December 8.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Venous thromboembolism (VTE) is a term few people have heard. It's the new name for blood clots inside veins. It includes deep-vein thrombosis and clots that break off and travel to the lung. These travelling clots are called pulmonary emboli. They can be deadly.
VTE is more common than most people appreciate. It affects more than 2 million Americans each year. About half of them require a hospital stay. Deaths from VTE may be as high as 200,000 yearly in the United States.
VTE is treated first with heparin. This drug is an anticoagulant, sometimes called a "blood thinner." It can stop a blood clot from getting larger and prevent new clots from forming. It can be given by shots under the skin or in a vein (intravenously).
In most cases, doctors prescribe warfarin (Coumadin) within a day or two after heparin therapy begins. Warfarin is an anticoagulant pill. Unlike heparin, which starts to "thin" blood right away, warfarin takes a few days to reach its full action.
People who have their first VTE are treated for 3 to 12 months with warfarin. Treatment can be as short as 3 months if the VTE occurred after an event known to cause a short-term risk of VTE. Examples of short-term risk include a long hospital stay or recent surgery, especially bone or joint surgery. For people with these short-term risks, warfarin usually can stop after 3 months.
But people who don't have a known risk factor need longer treatment. Doctors call these unprovoked VTEs. They require 6 to 12 months of treatment with warfarin.
People with unprovoked VTE also remain at risk for another event once warfarin stops. So why not continue warfarin for another year or two, or perhaps with no definite end planned? The main reason is the risk of major bleeding. Over time, the risk of bleeding becomes higher than the risk of another VTE.
Warfarin also is not easy to take. Doctors adjust the dose based on blood tests that need to be performed at least once every one to two months. For some people, getting the dose right can mean blood tests weekly.
Apixiban might offer a way to extend anticoagulant treatment for longer than a year. The results of this study suggest that it's effective, with no increased risk of bleeding. But it is only one study. And apixiban is not yet approved by the U.S. Food and Drug Administration (FDA).
Apixiban needs to be taken twice per day. And you can't skip doses. Warfarin is a once-per-day drug. The big advantage for apixiban over warfarin: no need for blood testing. Everyone takes the same dose.
Besides warfarin, two anticoagulant pills are FDA-approved. They are rivaroxaban (Xarelto) and dabigatran (Pradaxa). Doctors can prescribe them instead of warfarin in people with atrial fibrillation to help prevent stroke. Recently, the FDA approved rivaroxaban as an alternative to heparin plus warfarin for 6 to 12 months of treatment of VTE. Longer-term use of VTE has not yet been studied.
What Changes Can I Make Now?
Whether or not you have ever had VTE, here are some good ways to help prevent it:
- Stay physically active. At work or at home, get up from your chair often. Short walks contract the muscles in your legs that help pump blood back toward your heart.
- Drink plenty of liquids. This is especially important when you are going to be sitting for a long time, such as in an airplane.
- Move your legs. If you are bedridden and can't take frequent walks, contracting your leg muscles will help prevent blood from pooling and clotting.
- Maintain a healthy body weight. Obesity increases the risk of VTE.
- If you are in the hospital for some reason, ask your doctors and nurses to make sure you are receiving measures to prevent blood clots. These include wearing special stockings or getting low-dose heparin.
If you have had an unprovoked VTE, some doctors recommend taking warfarin for longer than 12 months. You and your doctor will decide on the benefits vs. risks. For those who stop warfarin, aspirin can also help prevent VTE recurrence. It's not as effective as warfarin. But the bleeding risk is lower.
What Can I Expect Looking to the Future?
Apixiban will likely get FDA approval next year. This one study does not mean that everyone with an unprovoked VTE should take the new drug after 6 to 12 months of warfarin. But for some patients with an especially high risk of another VTE, this may be a very good option.
As I noted, the FDA now approves using rivaroxaban instead of heparin plus warfarin for treatment of VTE. I personally will wait until this treatment has a longer record of equal effectiveness and safety before prescribing it.