Warfarin is often prescribed to prevent blood clotting and help combat the most common type of stroke, known as ischemic stroke. However, warfarin itself has been linked to intracerebral brain hemorrhage, another type of stroke caused by ruptured blood vessels and subsequent bleeding in the brain.
"Warfarin use increased during the 1990s, because it was proven to be effective in preventing ischemic strokes among people who have an abnormal heart rhythm called atrial fibrillation," said lead author and neurologist Dr. Matthew L. Flaherty.
Flaherty and colleagues from the University of Cincinnati collected information on all patients hospitalized with their first intracerebral hemorrhage during the years of 1988, 1993, 1994 and 1999 in the greater Cincinnati area. The researchers determined the annual rate of intracerebral hemorrhage associated with warfarin to be 0.8 cases per 100,000 people in 1988, but 4.4 cases per 100,000 people in 1999. The rate jumped from 2.5 per 100,000 in 1988 to 45.9 per 100,000 in 1999 for patients 80 and older.
"We are seeing more of these patients," noted Flaherty. "And we need better treatments once the bleeding has happened."
Flaherty said it was important that patients on warfarin get their International Normalized Ratio -- a test that measures blood's ability to clot -- monitored regularly as the drug can directly affect the INR and change it depending on what other drugs the patient is taking. An INR above three represents a greater danger of bleeding. He added that keeping blood pressure low was crucial because high blood pressure is already a risk factor for bleeding, and warfarin increases that risk.
Doctors also need to exercise caution about prescribing warfarin in the first place, Flaherty noted, especially in patients 80 and older.
"Some of those patients are better off being on warfarin," he said. "The message isn't that no one should use warfarin. There needs to be a balance between the benefit of preventing ischemic stroke and the risk of bleeding."
Dr. Michael B. Rothberg, an associate professor of medicine at Tufts University School of Medicine, said that doctors considering warfarin should first weigh the patient's risk of stroke against their risk of bleeding.
"This study demonstrates that we need to be careful when we use these therapies," he said. "Not all patients with atrial fibrillation should be getting warfarin. Patients at the highest risk for stroke will benefit the most, and patients at the highest risk for bleeding will benefit the least."
Flaherty said that more research should be performed to uncover drugs that are safer than warfarin.
"Right now, warfarin is the best medication we have for preventing ischemic strokes in patients who have atrial fibrillation," he said. "There are other drugs being worked on, but, right now, none of them are available."