Genetic Test Approved for Sensitivity to Blood Thinner

Some people who take Coumadin at higher risk of bleeding

TUESDAY, Sept. 18, 2007 (HealthDay News) -- The U.S. Food and Drug Administration has approved a genetic test to help doctors determine if a person is highly sensitive to the blood-thinning drug Coumadin (generic name: warfarin), increasing the risk of excessive bleeding.

About one-third of people who receive the drug, commonly prescribed to prevent dangerous blood clots, metabolize it differently, the FDA said. Two gene variants believed responsible for the unusual response are detected by the new test, produced by Northbrook, Ill.-based Nanosphere Inc.

After insulin, warfarin is the second most common drug implicated in emergency room visits for adverse reactions, the FDA said.

In August, the agency changed the drug's labeling to warn that people with variants of the genes CYP2C9 and VKORC1 could be more prone to excessive bleeding. One of the genes is responsible for an enzyme that helps the body process the drug; the other produces a blood-clotting protein that warfarin is designed to inhibit.

The new test is not meant to replace other diagnostics that help doctors determine the best dosage of the drug for each patient, which can be difficult. People who receive too high a dose are at risk of life-threatening bleeding, while those who get too low a dose could remain at risk of dangerous clots, the FDA said.

More information

To learn more about this approval, visit the FDA.

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