Jan. 9, 2003 -- Medications come in many different forms, from many different sources. But a vampire bat?

Research in this week's issue of Stroke: Journal of the American Heart Association says a rare protein in the saliva of vampire bats appears promising in the treatment of acute ischemic stroke — the kind of stroke caused by a blood clot that blocks blood supply to the brain.

Vampire bats are found throughout Central and South America. They have a wingspan of about eight inches and a body about the size of an adult's thumb. But it's their saliva that has medical researchers so excited. Some call it the most effective clot buster they've ever seen.

Once a vampire bat bites its sleeping prey it uses this remarkable saliva to keep the victim's blood flowing freely so that it can continue feeding for an indefinite period.

Now, scientists have now turned this clot-busting protein in the bat's saliva into a drug to dissolve the blood clots that cause a stroke. It's called Desmodus rotundus salivary plasminogen activator, or DSPA.

"In animal models, in preliminary research, this bat saliva clot-busting drug works faster, better and lasts longer" than the currently available drug, said Dr. Anthony Furlan, a stroke care specialist at the Cleveland Clinic Foundation and the principal investigator in the drug trial.

Current Drug Has Short Window

The problem with the one and only drug approved by the Food and Drug Administration for the treatment of acute ischemic, (rt-PA), is that it can only be given safely within the first three hours of a stroke. That's rarely enough time for patients to recognize the symptoms and get to a hospital.

As a result, only about two percent of stroke patients get the emergency treatment they need.

Early research suggests the drug made from bat saliva might be safe and effective hours later.

"The promise and excitement," said Dr. Furlan, "is that it can help many more patients with stroke. It can reverse paralysis. It can reverse blindness, restore the ability to speak and restore the ability of patient's ability to return to a relatively normal lifestyle."

Four medical centers in the United States, including the Cleveland Clinic Foundation and the University of Kentucky at Lexington have ordered the bat saliva drug for their emergency rooms and will soon begin testing the compound on stroke patients. Similar studies are already underway in Europe and Asia.

"I think it has the potential for being safer than the existing clot busting drug," says Dr. Creed Pettigrew of the University of Kentucky College of Medicine and one of the investigators.

Pettigrew says the bat saliva drug appears to target blood clots much more specifically and, in animal studies, "has shown much less potential for causing bleeding complications in other parts of the body."

"I think it will revolutionize the way acute stroke care is rendered in this country," he says. "I think it has that potential."

Researchers say they should know within the next two years whether the bat saliva drug lives up to its potential.