Heart Patients May Have New Medicinal Snake

Blood thinner from venom should be safer, easier to use

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By
HealthDay Reporter

TUESDAY, Dec. 30, 2003 (HealthDayNews) -- Coumadin, the popular but troublesome blood thinner, may soon have to make way for a new drug that seems to work more predictably and safely. Patients will have researchers to thank, along with a not-quite-usual suspect: the cobra.

The drug, derived from cobra venom, is expected to reach pharmacies within 18 months under the brand name Exanta. Its manufacturer announced last week it has submitted the drug to the U.S. Food and Drug Administration (FDA) for approval.

Experts say the drug could save time and reduce risks for millions of patients who face potential heart attacks and stroke.

"It would bring a dramatic change to how cardiologists practice," says Dr. Jonathan Halperin, a professor of medicine at Mount Sinai Medical Center in New York City. "This would be an important step forward if the drug is safe and available."

Coumadin, also known by the generic name warfarin, has been on the market for almost 60 years. It thins the blood, reducing the likelihood of blood clots that can block arteries and contribute to stroke or heart attack. The drug is often a second line of defense after aspirin, which prevents blood clots in a different way and is not as powerful.

But taking Coumadin is not as simple as just popping pills. "The problem with warfarin is that everybody absorbs it a little differently. People have to have frequent blood monitoring to adjust the dose," says Dr. Howard Herrmann, director of cardiac catheterization and interventional cardiology at the University of Pennsylvania.

The blood tests are typically required at least once a month. If patients and doctors don't work together to keep an eye on the levels of Coumadin in the body, the blood can become too thin (raising the risk of internal bleeding or hemorrhaging after an accident) or too thick (raising the risk of a clot). Since Coumadin works by interfering with the body's absorption of vitamin K from food, even a minor change in a person's normal diet can disrupt Coumadin levels.

To make matters more complicated, Coumadin interacts with a variety of drugs, making them work improperly or vice versa. "Antibiotics are frequent offenders, as are drugs used to control high cholesterol," Halperin says. "There are hundreds if not thousands of drugs. The list alone goes on for five pages."

Essentially, Halperin says, "a more effective anticoagulant is needed," especially for patients for whom aspirin isn't sufficient.

Here's where Exanta, also known as ximelagatran, comes in. It's derived from the venom of the cobra, which seems to render victims powerless by thinning their blood.

While it has not received federal approval yet, recent studies have reported the drug manages to thin the blood at a steady level without major fluctuations, unlike Coumadin. Patients wouldn't need to undergo regular blood tests to check the thinness of their blood.

"It's given in a fixed dose, and has no significant food or drug interactions," says Halperin. "It's almost like one-size-fits-all."

The drug's manufacturer, AstraZeneca, is seeking FDA approval to offer the drug as a treatment for people with atrial fibrillation (a potentially dangerous irregular heartbeat) and others at risk of blood clots.

Experts caution however, that while Exanta may be a great improvement upon Coumadin, it won't be perfect. The drug appears to affect liver enzymes in about 6 percent of patients, although they did fine later, Halperin says.

"It will be appropriate that people who begin should have certain blood tests taken from time to time to make sure they and the medicine are getting along well with one another," Halperin says.

Then there's the matter of cost. New drugs, not surprisingly, typically cost much more than drugs that are a half-century old. But experts say doctors will save time by not having to order and review monthly blood tests. More cost savings could come if fewer people have strokes because Exanta is easier to use than Coumadin.

According to the manufacturer of Exanta, studies have shown blood thinners reduce the incidence of stroke by 62 percent in patients at risk, but only half of them get the optimal treatment.

On the whole, Halperin says, "there's a good chance that a drug like this could replace warfarin for most people."

More information

Learn about blood thinners from the Texas Heart Institute. Curious about snake venom? Try cobras.org.

SOURCES: Jonathan Halperin, M.D., professor, medicine, Mount Sinai Medical Center, New York City; Howard Herrmann, M.D., director, cardiac catheterization and interventional cardiology, University of Pennsylvania, Philadelphia

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