If asked what the most dangerous prescription drug was, what would you answer? Given the news about opioid addiction, a lot of people would likely answer something like OxyContin or fentanyl.

As it turns out, according to a recent report published by the Institute for Safe Medication Practices (ISMP) the prescription medications most likely to require an emergency room visit are anticoagulants – also known as blood thinners. These include drugs like Xarelto, Pradaxa, and warfarin, all of which use different biochemical interactions to prevent blood from clotting.

Based on CDC data analyzed by the ISMP, there were nearly 22,000 severe injuries, including more than 3,000 deaths, reported by patients and health care workers relating to blood thinners last year. Of those, nearly half of the adverse events required a hospital stay. These are just some of the reasons that so many have taken legal action by filing Xarelto lawsuits recently, a reminder of the $650 million Pradaxa lawsuit settlementannounced by Boehringer Ingelheim in 2014.

But this only tells part of the story. Because the FDA only tracks voluntary reports, the true number of people injured by blood thinners each year is significantly higher. In fact, a different CDC study indicates that the annual number of people harmed by anticoagulants could be as much as ten times greater than voluntary reports indicate, reaching nearly a quarter of a million people.

Why Are Blood Thinners So Dangerous?

Blood thinners interrupt the blood clotting process, which is useful for treating or preventing certain medical problems that can be caused by blood clots, including strokes, pulmonary embolisms, deep vein thrombosis, and atrial fibrillation. The risk of blood clots are typically very high after certain types of surgery (such as knee or other joint replacement) and for people who tend to live a sedentary lifestyle.

The problem with blood thinners is that blood clots are sometimes a good thing. When you cut yourself, you want the blood to clot so that you stop bleeding. If blood didn’t clot, then even something as small as a tiny scratch could cause someone to eventually bleed out and die (known in the medical community as exsanguination). Thankfully, most people have blood that clots normally, so this situation does not occur.

When taking a blood thinner, however, the medication interrupts the natural formation of blood clots. Depending on the specific type of blood thinner you are taking (anticoagulant or antiplatelet), the mechanism works a little differently. But the end result is the same, in that your blood will be prevented from clotting.

The good news is that some blood thinners – like warfarin (Coumadin) – have “antidotes” to reverse their effects. If a person taking warfarin sustains an injury, a medical professional can administer some vitamin K to reverse the effects of the drug and restore the blood’s normal clotting behavior.

However, not all blood thinners have such antidotes, and others that have antidotes today did not have them until very recently. For example, the antidote for Pradaxa was only approved in 2015, so anyone taking the drug before then was at a risk of severe bleeding if they injured themselves. Individuals taking Xarelto still have that risk today, since no antidote for the anticoagulant has yet been approved by the FDA.

Minimizing the Dangers of Blood Thinners

Given that blood thinners are so dangerous, what can be done to reduce their effects? Here are a few ideas:

To be sure, blood thinners are legitimate medications with many beneficial uses for many people. However, using them safely and understanding their potential harms is an important part of making sure they remain helpful to people rather than harmful.