I thought Pradaxa was a good medication, so why is the doctor advising against it?

Kevin45 asked...

Advised Against Pradaxa.

My 86 year old father suffered a ischemic stroke four years ago that was caused by AFIB. He has been on Coumadin (warfarin) ever since and has a well maintained INR of 2 to 3. I asked his cardiologist to switch to Pradaxa, the new anticoagulant, to avoid the weekly blood testing and diet restrictions. He said he no longer blanketly recommends the switch for patients with well controlled INRs. The doctor said his hospital experienced several Pradaxa "failures." These were thrombolytic events - blood clots to the brain with bad outcomes.

I read the testing for Pradaxa was one of the largest ever, with extremely positive results. What happened here?

Expert Answer

Pharmacist William Simonson, also known as "Dr. Si", is a board-certified geriatric pharmacist who is dedicated to improving medication use by seniors. He is a pharmacy educator and is active in publishing and presenting to health professional and consumer audiences and has been active in the area of geriatrics and long-term care pharmacy practice for more than 35 years.

Atrial fibrillation (Afib) is a relatively common disorder of heart rhythm that increases in prevalence with advancing age. More than 2 million Americans have Afib and almost 1 in 10 over age 80 have this condition. Because it causes a disruption of the smooth flow of blood through the heart a significant risk of this condition is the formation of small clots in the heart that can move to other parts of the body, such as the brain, resulting in a stroke.

Before I answer your question I would like to disclose that I am a paid consultant and speaker for a number of different pharmaceutical manufacturers including the company that makes Pradaxa. That being said I will answer your question without bias or inaccuracy. My mission is to optimize drug therapy in seniors and I would not jeopardize my hard-earned reputation by giving you a commercial or slanted message.

Warfarin has been available as a prescription drug for 50 years. It is a powerful product and is quite effective in reducing the risk of stroke when used appropriately but, unfortunately, it is a difficult medication to use. Blood tests must be routinely drawn to measure the effect of the drug in order to modify the dose if necessary. Too much warfarin can result in bleeding which can be life-threatening. Too little, and the risk of stroke increases. Plus, warfarin interacts with many different prescription and non-prescription drugs as well as a number of different foods.

For years health professionals have wished for a drug that could do the work of warfarin without the associated inconvenience and danger. A few years ago such a drug almost came to market, but it was found to be toxic to the liver and was not approved by the Food and Drug Administration. Pradaxa was recently approved by the FDA as the first oral medication to reduce the risk of stroke and systemic embolism in patients with non-valvular atrial fibrillation (that means atrial fibrillation that is not caused by defects in heart valves and it is the most type of Afib). Pradaxa was studied in clinical trials and was found to be at least as effective as warfarin in reducing the risk of strokes in patients with this type of Afib.

As you know, routine blood monitoring is not required when taking Pradaxa, nor is Pradaxa associated with as many potential drug interactions which are significant potential advantages over warfarin. One important caution is that while warfarin may result in bleeding episodes, any medication that influences blood clotting, including Pradaxa, may also result in bleeding complications so that is always something to monitor.

Apparently your Dad's cardiologist prefers to continue using warfarin based on his experience and from discussions with colleagues and that is certainly his prerogative. Warfarin has been the "gold standard" for decades and in spite of its problems it effectively reduces the risk of stroke. I don't know anything about the failures that the cardiologist reported but my first question is "Were these patients actually taking their Pradaxa twice a day, every day?" It is crucial that patients are totally compliant when taking Pradaxa in order to benefit from the stroke risk reduction. Skipping doses and not taking the drug as prescribed will increase the risk of stroke so that could be what happened, but of course I am only speculating. And, it is important to understand that, even when taken correctly, neither warfarin or Pradaxa totally prevent stroke, they only reduce the risk of stroke.

Unfortunately, stroke reduction is not a perfect science. As clinicians and scientists make more discoveries hopefully some day we will be able to completely prevent this serious condition.