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If you’re one of the 2.7 million Americans who have atrial fibrillation, you have an increased risk of a stroke. You can greatly reduce the risk of a stroke by 50% to 60% by taking a blood thinner (anticoagulant).
A stroke occurs when blood flow to the brain is blocked by a clot, depriving brain cells of oxygen. In people with atrial fibrillation, blood flow is sluggish in the top chambers of the heart, and blood clots can form there. When a piece of a clot breaks off, it can travel to the brain and cause a stroke. That’s where blood thinners come in. Blood thinners, or anticoagulants, decrease the chances of blood clots forming in the heart, reducing the risk of stroke.
But as many as half of the people with atrial fibrillation who could benefit from a blood thinner don’t take them. There are two main reasons for this: Anticoagulants don’t affect how patients feel, and they can cause bleeding.
“Most drugs are used to improve how patients feel or function, but anticoagulants aren’t used this way. They are preventive drugs, used to prevent strokes in people who generally feel well,” says Ellis F. Unger, M.D., the Director of FDA’s Office of Drug Evaluation I in the Office of New Drugs.
“When treatment is successful, patients dramatically reduce their risk of experiencing a stroke, but the drugs don’t improve the symptoms of atrial fibrillation,” Unger adds. “So patients don’t feel any noticeable benefit while taking them. But they are well aware of the downside of the drugs — their inconvenience, bleeding side effects, and cost. But when patients avoid anticoagulants for these reasons, they put themselves at risk of irreversible brain damage and disability. The benefit of a decreased risk of stroke clearly outweighs the risks and inconveniences of these drugs.”
FDA has approved four blood thinners in recent years — dabigatran (Pradaxa), rivaroxaban (Xarelto), apixiban (Eliquis), and edoxaban (Savaysa). Along with warfarin, a drug approved 60 years ago, these drugs are used to prevent stroke in patients with atrial fibrillation.
There are some important differences among these drugs. Warfarin interacts with certain drugs and foods that make it less effective or more likely to cause bleeding, and so its effects must be monitored with periodic blood tests. The new drugs have fewer interactions and don’t require blood monitoring.
Although all anticoagulants reduce the risk of a stroke caused by clots from the heart, they increase the risk of a stroke caused by bleeding into the brain (a hemorrhagic stroke). The newer drugs cause fewer bleeding strokes than warfarin, and the overall rates of strokes (caused by blood clots or bleeding) are lower with some of the newer drugs.
Another difference is how fast the drugs start and stop working. “When starting warfarin, it takes a few days before the drug takes effect,” Unger says. “And when stopping warfarin, it takes a few days for its effects to wear off.”
He adds: “The new drugs start working rapidly, and their effects wear off fairly rapidly. For most patients, this is an advantage.”
He cautions: “Rarely, however, when patients have life-threatening bleeding or need urgent surgery, it can be important to stop the effects of these drugs immediately.”
For the rare patient with life-threatening bleeding, reversal agents can be used to counter the effects of anticoagulants. For example, Vitamin K is the reversal agent for warfarin. FDA recently approved the first reversal agent — Praxbind (idrucizumab) — for Pradaxa. Praxbind can be used in emergency situations when bleeding caused by Pradaxa’s anticoagulant effects can’t be controlled.
Strokes are often devastating to patients and their families.
“A stroke can ruin a life — or end one. Having a stroke can affect your ability to speak, eat, walk, work, care for yourself, and interact with others,” Unger says. Why don’t more people take blood thinners? “Both warfarin and the new drugs can cause bleeding, and we think fear of bleeding is the main reason many patients do not use them,” he says.
But most bleeding is not serious. It can be as minor as what occurs when you brush your teeth or shave. More serious bleeding, such as internal bleeding, can occur, but it’s rarely life-threatening, he says.
“Bleeding is scary, but it is usually treatable and unlikely to cause permanent damage,” he adds. “And it’s much less dangerous overall than a stroke.”
If you have atrial fibrillation, talk to your health care provider to make sure you’re being treated properly to prevent stroke. Some factors increase the likelihood that you will have a stroke. They include being 65 or older, having a history of previous stroke, diabetes, high blood pressure, and heart failure. The risks are also higher in women, patients with diminished kidney function, and people with a prior heart attack.
Some patients believe that because their atrial fibrillation is “mild” there is no need for them to take a blood thinner. They may have this impression because their atrial fibrillation causes few symptoms, or because it comes and goes. In fact, their risk of stroke has more to do with other factors and might be quite high, Unger says. So even if you have mild atrial fibrillation or atrial fibrillation that comes and goes, you should have a frank talk with your health care provider about treatment options.
FDA continues to work with manufacturers that are studying drugs to reverse the effects of some of the new anticoagulants, Unger says. “We hope these drugs will reduce the consequences of bleeding in some patients, and increase acceptance of anticoagulants in the medical community so that fewer patients with atrial fibrillation go untreated,” he adds.
When the new anticoagulants were being studied, the emphasis was on showing that they worked well compared to warfarin, without the need for blood monitoring. Since then, there has been more interest in individualized treatment. For example, this might include using the new drugs with occasional blood monitoring to further reduce the risks of stroke and bleeding.
“Too little use or underuse of anticoagulants in people with atrial fibrillation is a critical, preventable, public health problem. For most patients with atrial fibrillation, taking an anticoagulant as prescribed is the most beneficial thing you can do to reduce your chance of having a life-changing stroke,” he says.
This article appears on FDA’s Consumer Updates page, which features the latest on all FDA-regulated products.
October 16, 2015