Abnormal Heartbeat Rx May Pose Major Bleeding Risk

Dabigatran to prevent strokes in atrial fibrillation patients may cause more bleeding than warfarin, but warfarin may have higher intracranial bleeding risk

(RxWiki News) When the US Food and Drug Administration (FDA) approved dabigatran in 2010, it highlighted the medication's ability to prevent stroke. Since then, some have raised concerns that the blood-thinning medication may cause severe bleeding.

The FDA gave dabigatran its stamp of approval based on a trial that showed it may be better than warfarin — another blood thinner — for stroke prevention in patients with atrial fibrillation (AFib or AF). That study also found no significant differences between the medications when it came to major bleeding.

A new study, however, has found that dabigatran may be linked to a higher rate of major bleeding and a higher risk of stomach and intestinal bleeding than warfarin. On the other hand, warfarin may come with a greater risk of intracranial hemorrhage (bleeding within the skull).

Warfarin (brand names Coumadin and Jantoven) has been used for many years to ward off stroke in patients with AFib (an irregular heart beat). Dabigatran (brand name Pradaxa) reduces blood clotting in arteries, veins or the heart. It is also prescribed to prevent stroke in AFib patients.

Inmaculada Hernandez, PharmD, a researcher with the University of Pittsburgh, and colleagues wrote the study.

They reviewed Medicare data on patients newly diagnosed with AFib from October 2010 to October 2011. A total of 1,302 dabigatran users and 8,102 warfarin users were represented. The American Heart Association estimates that 2.7 million Americans have AFib. AFib is a common heartbeat abnormality in people older than 65.

Nine percent of the dabigatran patients and 5.9 percent of the warfarin group had major bleeding, the study authors found.

The rates for any type of bleeding were 32.7 percent in dabigatran users and 26.6 percent for those taking warfarin. Dabigatran was tied to a greater risk of blood in the urine (hematuria), vaginal bleeding, bleeding in joint spaces (hemarthrosis) and coughing up blood (hemoptysis). The risk of stomach and intestinal bleeding was especially high. Dabigatran users were 85 percent more likely to have this condition than warfarin users.

Blacks and those with kidney disease who took dabigatran faced an especially high risk of major bleeding. Their risk was about twice that of the corresponding groups — blacks and patients with kidney disease — who were taking warfarin.

The risk of bleeding when taking warfarin was only higher than the risk with dabigatran when it came to bleeding in the brain, the study authors found.

Sarah Samaan, MD, FACC, cardiologist and physician partner at the Baylor Heart Hospital in Plano, TX, told dailyRx News that warfarin was the only blood thinner option for years to help prevent stroke in AFib patients. She warned, however, that warfarin can be cumbersome to use, since blood levels have to be monitored closely. Diet, other medications and illness can affect the levels.

On the other hand, she said that dabigatran can be taken at the same dose every day, and only routine blood testing once or twice yearly is usually required.

"This study shows us that we have to be very vigilant for any signs of gastrointestinal bleeding, since there appears to be higher risk with dabigatran than indicated by the initial studies of the drug," Dr. Samaan said. "On the other hand, bleeding into the brain, the most feared and dangerous bleeding complication, appears to be lower with dabigatran than warfarin. And other studies have found that the drug is superior to warfarin in preventing strokes."

Dr. Samaan advised patients taking dabigatran to be sure to let their doctors know of any worrisome stomach trouble, blood in the stools or any other gastrointestinal concerns.

This study was published online Nov. 3 in JAMA Internal Medicine.

A grant from the Commonwealth Foundation and the Agency for Healthcare Research and Quality funded the research. The authors disclosed no conflicts of interest.

Review Date: 
November 6, 2014