The pros and cons of atrial fibrillation medications

DEAR DR. ROACH: I was put on Coumadin several years ago for atrial fibrillation. It was a perpetual pain in the butt, all those tests and never knowing from day to day how much the blood had been changed from meal to meal. Both extremes were dangerous. I had two friends on Coumadin who were in remote areas when they fell, both hitting their head. Both died from brain hemorrhage before they could be treated at a hospital. My doctor suggested Pradaxa, a more expensive product, but with no testing required. From what I read, there is no more danger of internal bleeding from one than from the other, and apparently Coumadin can be reversed medically in an emergency room while Pradaxa cannot (true or false?).

It would be helpful for you to explain the chemical/medical differences between the two drugs; how they work and why they work differently; and an opinion as to which is the safer to use, and why. – C.L.

ANSWER: Atrial fibrillation, the chaotic beating of the upper part of the heart, puts people at higher risk for blood clots, and is one of the most common reasons to prescribe warfarin (Coumadin). Warfarin really did start off as rat poison, but, like many drugs, it's useful as a medicine in small doses even if it is potentially deadly in high doses. It has been in use for 60 years.

Unfortunately, it is ineffective if you don't give enough and can cause serious bleeding if too much is given, as happened to your friends. The INR blood test (international normalized ratio) is used to determine the correct dose, and the usual desired range is 2-3, although people with mechanical heart valves need a slightly higher dose, 2.5-3.5. Blood testing needs to be done at least every few weeks, and much more often when just starting and in people whose levels go up and down.

Since warfarin works by blocking vitamin K, people on warfarin need to have a consistent vitamin K intake, which is mostly found in green, leafy vegetables. Vitamin K will reverse the effects of warfarin in half a day or so, but blood products can be used to immediately reverse the effect.

Dabigatran (Pradaxa) is a new medication that works by directly blocking thrombin, a key protein in making clots. Dabigatran should not be given to people with poor kidney function or disease of heart valves. There is no way to reverse its effects.

Studies comparing warfarin and dabigatran have shown similar rates of effectiveness and a slightly lower risk of brain hemorrhage with dabigatran. Some studies show a slightly higher risk of heart attack in people taking dabigatran.

In my opinion, both are reasonable choices. Pradaxa may be more convenient since it doesn't require testing and appears to be about as effective, and with a lower risk of brain hemorrhage. However, there is no antidote, and it needs to be taken twice daily.

READERS: Atrial fibrillation affects some 2 million Americans. To learn more, order the booklet Heartbeat Irregularities by writing: Dr. Roach – No. 107W, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient's printed name and address. Please allow four weeks for delivery.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected]. To view and order health pamphlets, visit rbmamall.com, or write to P.O. Box 536475, Orlando, FL 32853-6475. (c) 2014 North America Synd. Inc. All Rights Reserved