Genetic Variation Can Affect Warfarin Doses for African Americans

A genetic variation that affects how some black patients respond to blood thinners could improve the effectiveness and safety of the drug, warfarin.

According to the study, those found with the genetic variation may need a significantly lower dose than others.

"Adding this genetic marker -- found in more than 40 percent of African-American patients in the study -- to standard dosing algorithms improved the predictability of warfarin dosing by 21 percent in these individuals, which has the potential to increase the safety and effectiveness of this notoriously hard-to- dose drug," study leader Julie Johnson, of the University of Florida, said in a journal news release, according to U.S. News and World Report.

Previous studies have identified two genes that account for approximately 30 percent of the difference seen in warfarin responses for people of European and Asian ancestry. However, these genes have less of an effect in blacks.

Study authors analyzed health information and DNA samples from hundreds of blacks to determine that there was a strong association between the rs12777823 variant on chromosome 10 and warfarin dose.

These findings may suggest that various lower doses of the drug are required for blacks with one or two copies of the variant. Researchers say this could be anywhere from 7 to 9 milligrams (mg) less per week.

The drug is often used to help prevent blood clots from forming or growing larger in patients blood and blood vessels. It's often prescribed for people with various types of irregular heartbeat, prosthetic (replacement or mechanical) heart valves and people who have suffered a heart attack. It can also be used to treat or prevent venous thrombosis and pulmonary embolism.

However, health officials note that it can be difficult to prescribe the correct amount for certain individuals, and side effects can be risky and even result in death. 

The researchers report online June 4 in The Lancet.