Anticoagulants are often given to patients with a type of heart rhythm abnormality known as atrial fibrillation to prevent strokes. The reasoning is that in people with atrial fibrillation, the upper chambers of the heart pump abnormally causing blood to pool in the atria. When that happens, blood clots are more likely to form. If a blood clot gets pumped out of the heart and lodges in a blood vessel in the brain, it can cause a stroke. Anticoagulants thin the blood and help prevent clots from forming, which, in turn, help prevent strokes from occurring in patients with atrial fibrillation.
For decades, doctors widely used the blood thinner warfarin, also known by the brand name Coumadin, to treat atrial fibrillation patients. However, the dosing can be tricky and is not always uniform in patients. If the dosage is too low, a clot can form. It if is too high, bleeding problems can occur.
Another factor is that there are a lot of contraindications associated with warfarin, which can increase or decrease its anticoagulant quality. Thus, patients who are given warfarin also have to be monitored on a regular basis to ensure the proper level of drug is in their systems.
In 2010, the Food and Drug Administration (FDA) approved a new alternative to warfarin for atrial fibrillation patients. Pradaxa (dabigatran) was almost an instant hit with doctors and patients alike because, unlike warfarin, patients on the medication did not need regular monitoring because its effect on the blood is more predictable. It also appeared to be just as effective as warfarin at preventing strokes in atrial fibrillation patients.
However, there are two risks associated with Pradaxa. First, the drug has a short half-life, meaning that it is almost completely out of one’s system after 24 hours. Thus, patients who miss a dose are more at risk for developing a blood clot than if they miss a dose of warfarin. Secondly, there are no antidotes available that can reverse the coagulant effects of Pradaxa once it is in the system. Thus, there is nothing available to thicken the blood in patients who are injured and start bleeding profusely. This contributes to the concern with Pradaxa. In the first 14 months since the drug hit the market, it was associated with more than 900 gastrointestinal bleeds and 500 bleeding deaths.
Researchers are currently working on reversal agents for Pradaxa but they could take years to reach the market. There are currently antidotes available for warfarin.