A new study being published in the September 30, 2008, print issue of Neurology, the medical journal of the American Academy of Neurology, states that patients taking the popular blood thinner warfarin may have larger amounts of bleeding in the brain and experience an increased risk of death if they suffer a hemorrhagic stroke. Warfarin is commonly prescribed to prevent blood clotting. The study was supported by the National Institute of Neurological Disorders and Stroke as well as a University of Cincinnati College of Medicine Medical Student Summer Research Fellowship.
Studies indicate warfarin helps prevent ischemic stroke for those patients with an abnormal heart rhythm called atrial fibrillation, but if warfarin overthins the blood, there is an increased risk of brain hemorrhage, a type of stroke caused by bleeding in the brain.
The study involved 258 people who had suffered brain hemorrhage, 51 of whom were taking warfarin. On average, patient participants were 69 years old and lived in or near Cincinnati. To confirm the type of stroke they had suffered, the group underwent brain scans, which were also used to measure the size of the blood clots. The study revealed that those who took warfarin and suffered a brain hemorrhage while their international normalized ratio (INR) was above three had about double initial bleeding as those not taking warfarin. This effect was not seen in people whose blood was less likely to clot; this was determined by an INR of under three. INR tests measure the blood’s ability to clot.
“Warfarin is very effective for preventing ischemic strokes among people with atrial fibrillation and for most patients with this condition it is the right choice,” said study author Matthew L. Flaherty, MD, with the University of Cincinnati and member of the American Academy of Neurology. “However, people who have bleeding into the brain while taking warfarin are at greater risk of dying than other people with hemorrhagic stroke. Our study may help to explain why. Fortunately, we did not see larger blood clots in people with an INR of less than three. For most patients on warfarin, the goal INR is between two and three. This shows the importance of good monitoring and adjustment of warfarin dose. People should talk to their doctors about the proper management of warfarin and learn the signs of stroke so they can get to an emergency room immediately if a stroke occurs.”
Late last year we reported that warfarin was among a few drug whose side effects send more senior citizens to the emergency room than any other medications because the correct dosages for warfarin are extremely difficult to determine.
Warfarin is also known under the brand names of Coumadin, Jantoven, Marevan, and Waran and is administered orally or, very rarely, by injection. It is used to prevent blood clots and embolisms, and is often prescribed to people with a history of stroke and heart attacks. Hemorrhage is a common side effect of warfarin. Between 2004 and 2005, warfarin adverse reactions resulted in 58,000 ER trips per year by senior citizens.
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