Q. For several years, I have been taking warfarin because of atrial fibrillation. I recently suffered several nosebleeds, which took two days to control. The trauma of those episodes makes me want to swear off warfarin, but I am not sure what other options I have.
A. People with atrial fibrillation are at risk of having a stroke because when the atria (the top two chambers of the heart) fibrillate (beat chaotically), blood collects in the heart, giving clots a chance to form. One of those clots can travel to the head, get stuck in a blood vessel there, and cause a stroke.
Warfarin prevents blood clots by blocking the activity of vitamin K. It’s a good, time-tested drug. But warfarin is tricky to use. You’ve experienced firsthand the bleeding problems it can cause. Yet if you rake back the dose too far to avoid bleeding, you’re back to where you started: running the risk that a blood clot may form and cause a stroke. Doctors try to steer people down the middle by monitoring them with international normalized ratio (INR) tests, which measure how fast the blood clots, but people’s response to warfarin is variable, and the drug interacts with a lot of food and medications. A good alternative to warfarin has been on the wish list of many “afib” patients — and their doctors — for years.
Dabigatran (pronounced dah-BIG-ah-tran) might be that alternative. It was approved by the FDA in 2010 and is available only as a brand-name drug, Pradaxa. It acts directly on thrombin, one of the key players in the formation of blood clots. Well-designed research trials have shown that it provides as much protection against stroke as warfarin but is less likely to cause bleeding complications. And because it’s absorbed and used by the body in a more consistent manner than warfarin, people don’t need to be monitored with INR tests.
Sounds great so far. But here are three cautions. First, the largest randomized trial of dabigatran purposely excluded several types of patients, including people with severe heart valve disorders, those who’ve had a stroke within the previous 14 days or a severe stroke within six months, and anyone with kidney problems or active liver disease. So if you have one of those problems, you might not be a good candidate for switching to dabigatran. Second, a year’s supply of dabigatran costs in the neighborhood of several thousand dollars. Generic warfarin costs several hundred. Even if you have insurance, dabigatran could cost you more because of higher co-pays. Third, we have a lot of experience with warfarin. It’s the devil we know. Dabigatran looks safe and effective based on trial results, but a different picture may emerge once tens or even hundreds of thousands of people start taking it.
You should talk about dabigatran with your doctor. If you’re not a candidate for a switch, then you should talk to him or her about possible food and drug interactions with warfarin and perhaps more careful monitoring. Don’t stop taking warfarin on your own. As bad as the nosebleeds were, they’re less serious than the stroke that could occur if you quit warfarin.
— Thomas H. Lee, M.D.
Partners Healthcare System, Boston
Harvard Health Letter Editorial Board