Pradaxa, an anticoagulant medication made by the pharmaceutical company Boehringer Ingelheim, has become controversial because of its alleged association with an increased risk of excessive bleeding.

Recent studies have explored the pros and cons of taking Pradaxa as opposed to the older anticoagulant warfarin, also sold under the brand name Coumadin.

Pradaxa is part of a new generation of blood thinners, along with Xarelto (rivaroxiban) and Eliquis (apixaban), that entered the market relatively recently, which had been dominated by warfarin.

These newer anticoagulants are approved by the FDA to treat atrial fibrillation, and they are also frequently prescribed for off-label use as treatments for deep vein thrombosis or blood clots. They work by thinning the blood and reducing its ability to clot. The disadvantage to that mechanism is that it makes bleeding episodes more serious.

One major selling point common to these new medications is that they do not require regular monitoring and dosage adjustments, as does warfarin. However, unlike warfarin, these new drugs do not have what’s called a “reversal agent” or an antidote, which is a complementary drug that can stop excessive bleeding.

Once excessive bleeding starts when someone is taking Pradaxa, it does not stop until the body rids itself of the drug. In November 2014, Boehringer Ingelheim submitted a new drug, idarucizumab, for FDA approval as a reversal agent for Pradaxa bleeding. FDA approval for that drug is still pending.

Studies Compare Pradaxa to Warfarin

A study published online in the American Heart Association’s journal Circulation in October 2014 examined the differences in side effects between Pradaxa (identified by its generic name dabigatran in the study) and warfarin.

The study followed over 134,000 elderly Medicare patients between October 2010 and December 2012. In patients who took two 150 milligram doses of medication per day, researchers found those who took Pradaxa had less risk of ischemic stroke, intracranial hemorrhage, and death.

However, those patients had a greater risk of major gastrointestinal hemorrhaging compared to those who took warfarin. For those patients who took a smaller dose of 75 milligrams twice per day, the study found comparable outcomes between Pradaxa and warfarin except for a decreased risk of intracranial hemorrhage associated with Pradaxa.

Another study published online in JAMA Internal Medicine in January 2015 examined Medicare data from over 1,300 Pradaxa users and over 8,100 warfarin users from 2010 and 2011. The researchers found Pradaxa was associated with a higher risk of any kind of bleeding event and an 85 percent greater risk of gastrointestinal bleeding.

Among Pradaxa users, the risk of major bleeding was particularly high in African-American patients and those with chronic kidney disease. The study also found a lower risk of intracranial hemorrhage with Pradaxa than with warfarin.

Some scientists also question Boehringer Ingelheim’s claim that Pradaxa does not require ongoing monitoring. They say Boehringer’s own data shows wide variance in Pradaxa’s blood thinning effect from patient to patient, resulting in a given dose failing to provide its therapeutic effect in one patient and exposing another patient to an excessive risk of bleeding.

Symptoms of Pradaxa Internal Bleeding

The FDA warns Pradaxa patients to consult their physician immediately if they experience any of the following symptoms: unusual gum bleeding, frequent nose bleeds, heavier than normal vaginal bleeding, any bleeding that the patient cannot control, pink or brown urine, stools that are red or black or that look tarry, easy bruising, coughing up blood or clotted blood, or vomiting that appears to contain blood or looks like coffee grounds. These can all be symptoms of Pradaxa bleeding.