* pre-existing indication for anticoagulation (e.g., pulmonary embolism or deep vein thrombosis; atrial fibrillation; mechanical cardiac valve) * contraindication to antithrombotic therapy (e.g., known bleeding within the last 30 days requiring emergency room presentation or hospitalization; major surgery within 14 days; ischemic stroke, intracranial bleed or neurosurgery within 3 months. * platelet count \< 50,000/mcl * hemoglobin \<8 gm/dl * renal insufficiency (egfr \< 30 ml/min/1.73 m2) * pregnancy * prison inmate * life expectancy less than 90 days * unwilling or unable to provide informed consent/unwilling or unable to complete the study protocol * dual antiplatelet therapy that cannot be discontinued * concomitant need for strong inducers/inhibitors of p-gp or cyp3a4

* pre-existing indication for anticoagulation (e.g., pulmonary embolism or deep vein thrombosis; atrial fibrillation; mechanical cardiac valve) * contraindication to antithrombotic therapy (e.g., known bleeding within the last 30 days requiring emergency room presentation or hospitalization; major surgery within 14 days; ischemic stroke, intracranial bleed or neurosurgery within 3 months. * platelet count \< 50,000/mcl * hemoglobin \<8 gm/dl * renal insufficiency (egfr \< 30 ml/min/1.73 m2) * pregnancy * prison inmate * life expectancy less than 90 days * unwilling or unable to provide informed consent/unwilling or unable to complete the study protocol * dual antiplatelet therapy that cannot be discontinued * concomitant need for strong inducers/inhibitors of p-gp or cyp3a4

- pre-existing indication for anticoagulation (e.g., pulmonary embolism or deep vein thrombosis; atrial fibrillation; mechanical cardiac valve) - contraindication to antithrombotic therapy (e.g., known bleeding within the last 30 days requiring emergency room presentation or hospitalization; major surgery within 14 days; ischemic stroke, intracranial bleed or neurosurgery within 3 months. - platelet count < 50,000/mcl - hemoglobin <8 gm/dl - renal insufficiency (egfr < 30 ml/min/1.73 m2) - pregnancy - prison inmate - life expectancy less than 90 days - unwilling or unable to provide informed consent/unwilling or unable to complete the study protocol - dual antiplatelet therapy that cannot be discontinued - concomitant need for strong inducers/inhibitors of p-gp or cyp3a4

- pre-existing indication for anticoagulation (e.g., pulmonary embolism or deep vein thrombosis; atrial fibrillation; mechanical cardiac valve) - contraindication to antithrombotic therapy (e.g., known bleeding within the last 30 days requiring emergency room presentation or hospitalization; major surgery within 14 days; ischemic stroke, intracranial bleed or neurosurgery within 3 months. - platelet count < 50,000/mcl - hemoglobin <8 gm/dl - renal insufficiency (egfr < 30 ml/min/1.73 m2) - pregnancy - prison inmate - life expectancy less than 90 days - unwilling or unable to provide informed consent/unwilling or unable to complete the study protocol - dual antiplatelet therapy that cannot be discontinued - concomitant need for strong inducers/inhibitors of p-gp or cyp3a4