Often called “blood thinners,” these medications do not “thin” the blood. What they do is interfere with the blood’s ability to clot; medically, we call them “anticoagulants” (“coagulate” means “to clot”). They’re used to treat and prevent the formation of various abnormal blood clots, for reasons such as:
- Pulmonary Embolism: a blood clot in the lungs (if large, can be fatal), usually comes from a clot that began in leg or pelvic veins
- Deep Venous Thrombosis: blood clots in a vein, usually in the legs, usually for a specific reason (recent immobility due to cast or general anesthesia, cancer, pregnancy, etc.)
- Atrial Fibrillation: to prevent a clot forming in the heart that can then jar loose & flow to the brain, causing a stroke
- Metal Heart Valve: same risk as for Atrial Fibrillation, above
- Certain diseases that cause abnormal clotting: Lupus, some hereditary conditions, etc.
- NOTE that clots are dangerous when they form inside the blood stream, in veins or arteries. Bruises, which are clotted blood that has seeped out of our tiniest blood vessels (capillaries) into the skin, present no danger at all.
The main risk of anticoagulants is that, by preventing the blood from clotting appropriately, they can cause abnormal bleeding, which can also be fatal. We’re especially careful among people with known tendencies to bleed, & among the elderly who may fall more easily, with bleeding in the brain from even minor head trauma.
There are three kinds of anticoagulants (“blood thinners”):
- Warfarin (Coumadin®), the oldest type. It works well, but can be hard to manage, because it requires regular blood tests to be sure the dose isn’t becoming too high or too low. Dosing can change in the body for both known & unknown reasons, even though the dose of the pill is the same
- Direct Acting Anticoagulants, which are new (& thus quite expensive). They work as well as warfarin, and are easier to manage since there’s no need for regular blood testing. A disadvantage is that some of them have to be taken twice a day, and for some there’s no way to stop the drugs actions if a person has major bleeding & needs to clot. They can be used for the first 3 conditions listed above, but usually not the others, since they haven’t been studied for them. Examples include Dabigatran (Pradaxa®), Rivaroxaban (Xarelto®), Apixaban (Eliquis®), And Edoxaban (Savaysa®).
- Heparin: Injected, either IV or subcutaneously (under the skin). This is usually only used briefly, while transitioning to one of the first two medication, since long-term use of heparin can occasionally be dangerous.
Aspirin, Clopidogrel (Plavix®), and various other medications interfere with the body’s platelets, which are also necessary for blood clotting. These drugs are primarily used to prevent heart attacks, and for patients who’ve had strokes. We don’t call them “blood thinners” or “anticoagulants,” because they’re less powerful, & also less risky.