Moral of the story: Warfarin has a very narrow therapeutic index and genotyping will help to prevent complications that are so very common.

Source: AMA Morning Rounds 3/17/2010

Data indicates warfarin genotyping may reduce hospitalization rates.

USA Today (3/17, Sternberg) reports, "Doctors who used a genetic test to personalize treatment with warfarin, the world's most widely prescribed blood thinner, cut their patients' hospitalization rates by almost a third," according to a presentation made during the American College of Cardiology meeting. The study, led by Medco Health Solutions' Robert Epstein, "marks the first nationwide attempt to incorporate genetic testing into the routine use of a drug whose effects vary so much from one person to another that it carries a 'black box' warning, the government's most urgent safety alert."

        Apparently, "too much warfarin can lead to bleeding, too little can lead to clots, and either one can kill," the AP (3/17, Marchione) reports. Even "certain foods can throw it off," and "up to 20 percent of patients wind up in the hospital in their first six months on the drug." But Mayo Clinic trial participants "given gene tests to set their initial warfarin dose had about a 30 percent lower risk of being hospitalized than similar patients whose doses were set by trial and error."

        And, "Epstein said that the cost of the genetic testing -- $250 to $400 -- would be justified by reduced hospitalization costs," HealthDay (3/16, Preidt) reported. Notably, the "study included 896 people who, shortly after beginning warfarin therapy, gave a blood sample or cheek swab that was analyzed for expression of two genes -- CYP2C9 and VKORC1 -- that revealed sensitivity to warfarin."