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Utah heart doctors discover 75 percent of patients taking popular blood thinners are getting wrong dose

Published: Tuesday, Nov. 6 2012 9:10 a.m. MST

In this June 14, 2011 photo, the blood thinner medication Plavix is displayed at Medco Health Solutions Inc., in Willingboro, N.J. Because of decades of poor diets and insufficient physical exercise, and sometimes heredity, millions of Americans require daily medications to keep their blood flowing.

Matt Rourke, ASSOCIATED PRESS

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SALT LAKE CITY — Because of decades of poor diets and insufficient physical exercise, and sometimes heredity, millions of Americans require daily medications to keep their blood flowing.

The use of blood thinners before and after various heart surgeries is common, but doctors with Intermountain Healthcare have recently discovered that most patients are taking the wrong doses of at least two largely prescribed medications, and those patients may be at risk for unnecessary complications.

"There's a sweet spot, an appropriate range for each patient. But we found that not many people are falling into that range," said Dr. Brent Muhlestein, a cardiologist and cardiac researcher at the Intermountain Medical Center Heart Institute.

While the goal remains preventing coronary artery disease in the first place, once a person is diagnosed, proper use of medications can lead to better outcomes, Muhlestein said.

Heart disease, which leads to heart attacks and stroke, he said, is still the most common cause of death in the United States, as it accounts for more than half of deaths annually.

The new study found that of more than 520 patients tested at the hospital, 75 percent taking either clopidogrel (Plavix) or prasugrel (Effient) were receiving the wrong dose of their medication.

Current guidelines recommend that all patients take the same standardized dose, which is 75 milligrams per day for Plavix or 10 milligrams per day for Effient.

"We showed that by performing a simple blood test to see whether or not the blood is clotting properly, we can determine whether patients are getting an appropriate, individualized dose of the medications," Muhlestein said. "The test is easy to perform, but not widely used."

Using the Accumetrics VerifyNow System, blood is tested after a loading dose is given at the hospital, two weeks later to ensure maintenance dose is accurate and again if the dose is changed. If the blood flow is greater than 200, which means it is too thick, it could result in clotting or stroke. If it is less than 100, or too thin, bleeding complications can occur.

"If they are out of range, they are more likely to have complications. It seems like it would be beneficial to get them in range and improve their outcomes," Muhlestein said.

Drug companies, he added, can get approval for medications by testing just one dose and proving that it is better than no dose at all. So, there has been no need to conduct additional testing.

Half of the study's patients taking Plavix or its generic, clopidogrel, were getting too little of the drug to prevent clotting most effectively. A quarter were getting too much, and the remaining quarter were getting a more accurate dose.

Similar results were found for patients taking Effient or its generic, prasugrel, except half were getting too much of the drug, Muhlestein said. He will be presenting the findings of the Intermountain study at the American Heart Association Scientific Sessions 2012 in Los Angeles on Tuesday.

The study also found that there is no way to predict for which patients either drug would work, nor an appropriate dose. The blood test, which has to be done correctly, was the only way to differentiate dosage.

Finding the lowest effective dose of a medication for patients, Muhlestein said, could conceivably cut pharmacy bills in half.

E-mail: wleonard@desnews.com

Twitter: wendyleonards

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