The study goal is to conduct a randomized controlled trial to compare safety and accuracy of dosing based on clinical information including the clinical reason for your taking coumadin, your age, gender, your body surface area, and other medical conditions you may have with dosing estimated by a dosing calculator which adjusts for factors affecting coumadin dosing variability including genotypes for genes important in Coumadin metabolism and response. The hypothesis to be tested by this trial states that:when compared to patients managed with a best practices standard-of-care coumadin dosing regimen, patients randomized to coumadin dosing based on genetically programmed metabolic capacity and other known clinical and environmental factors affecting dose will: 1)show reduced risk of adverse events (using surrogate measures of such events); and 2)more rapidly achieve Coumadin dosing.

The study goal is to conduct a randomized controlled trial to compare safety and accuracy of dosing based on clinical information including clinical reason for taking coumadin, your age, gender, your body surface area, and other medical conditions you may have and dosing with dosing estimated by a dosing calculator which adjusts for factors affecting coumadin dosing variability including genotypes for genes important in Coumadin metabolism and response. The hypothesis to be tested by this trial states that:when compared to patients managed with a best practices standard-of-care coumadin dosing regimen, patients randomized to coumadin dosing based on genetically programmed metabolic capacity and other known clinical and environmental factors affecting dose will: 1)show reduced risk of adverse events (using surrogate measures of such events); and 2)more rapidly achieve Coumadin dosing

Inclusion Criteria:

• Caucasian male and female patients(including Hispanic white) greater than or equal to 40 years of age;
• Patients initiating coumadin therapy without a documented history of stabilized dose of coumadin therapy;
• Target INR of 2 to 3.5;
• Women of childbearing potential must use an effective method of birth control(e.g. condom,oral contraceptives, indwelling intrauterine device, abstinence.

Exclusion Criteria:

• Age less than 40 years;
• Patients of known Native American, Asian, or African descent;
• Patients with thrombocytopenia(platelet count<50x10 cells/ml);
• Patient has previously received coumadin and information on dosing of the patient is known at time of restarting coumadin;
• Patients with severe to moderate hepatic insufficiency (AST or ALT less than 2x the upper limit of normal;
• Clinical contraindication for coumadin therapy;
• Female patients with a positive pregnancy test or women who are breastfeeding